CHAPTER VII

Analytical Method Development

CHEMISTRY OF THE IRON-THIOCYANATE COMPLEX IN THE PRESENCE OF

SURF ACT ANTS AND OTHER REAGENTS

Analytical ShJdks on the Atmospheric /kposltions

ANALYTICAL METHOD DEVELOPMENT

CHEMISTRY OF THE IRON-THIOCYANATE COMPLEX IN THE PRESENCE OF SURF ACT ANTS AND OTHER REAGENTS

1. ABSTRACT

The sensitivity of the reaction between the iron(III) and thiocyanate is largely

dependent on the number of the thiocyanate ions co-ordinated with iron(III). The

reaction mechanism and composition of the iron(III)-thiocyanate complex in the

presence of the surfactant mixture is elucidated. This composition is compared with

few other reported complexes to describe the chemistry of the iron complexation. A

new spectrophotometric method for the trace determination of various chemical

species of iron has been developed and applied for its determination in the rainwater,

groundwater and the boiler feed water. In the method, iron(IIl) complexes with

thiocyanate ions in the presence of a cationic surfactant (e.g. CPC) and an anionic

surfactant (Tx-100). Other reagents evaluated in the conjunction with the cationic

surfactants are various amides. Molar absorptivities of the various thiocyanate

complexes in organic solvents with these reagents lie between (1.1-3.5) xl04 L mole ·l

cm·1 at absorption maxima between 460-500 nm. Effect of various reagents on the

spectral characteristics of the complex, optimisation of the analytical variables and the

effect of foreign ions has been described. None of the foreign ions tested in the

environment samples and boiler feed water interfered up to the normal levels

observed in the applications described. Iron is quantitatively pre-concentrated at the

least I 0-15 fold by the proposed method. The detection limit at 6-fold pre­

concentration is 4-ppb iron. The proposed method has been applied for the field

determination of total iron and its speciation in the above-mentioned samples.

Key words: Iron, spectrophotometry, thiocyanate, surfactants, amide, boiler feed water,

groundwater, rainwater.

}OJ

Analytical studies on tht Atmospheric Depositions

2. INTRODUCTION

Iron is one of the most widely distributed elements in the earth. It is also an essential

element biologically, required for a variety of enzymatic and biochemical reactions.

Iron is the major trace element identified in the atmospheric particulate near ferrous

metallurgical industries. Presence of higher concentration of iron in the boiler feed

water is an industrial problem. Chemical characterisation of iron is also required in

various other disciplines like toxicology, chemical process analysis, geology, aquatic

studies, etc. (Eljalde eta!., 1992; Beyer et al., 1975; Parry eta!., 1973, Zhu et al., 1992;

Anderson et a!., 1982). Major physico-chemical properties of iron are presented in

Table 1.

Table 1. Properties of Iron

Name: Iron

Name ..

Anglo-Saxon: iron; symbol Description: Malleable, ductile, silvery-white ongm: from Latin: ferrum (iron). metal. Fourth most abundant element in the

earth's crust (56,300 ppm). Ninth most abundant element in the universe.

Discovered by: Known to the ancients. Year: Unknown, Location: Unknown

Uses: used in steel and other alloys. Essential Sources: Obtained from iron ores. Pure metal for humans. It is the chief constituent of produced 1fi blast furnaces by layering haemoglobin, which carries oxygen in blood limestone, coke and iron ore and forcing hot vessels. Takes part 1fi vanous other gasses into the bottom. This heats the coke enzymatic reactions. Its oxides are used in red hot and the iron is reduced from its magnetic tapes and disks. oxides and liquefied where it flows to the

bottom

Symbol: Fe Group: Transition Metal

Crystal Structure: Cubic: Body centred Lattice parm. a: 2.8665 A Lattice parm. b: Lattice parm. c or axial angle:

Atomic number: 26 Atomic weight: 55.847

Shells: 2,8,14,2 Orbitals: (Ar) 3d• 4s2

Melting point: 1535°C Boiling point: 2861 °C

Electronegativity: 1.83 Covalent radius: 1.17 A Ionic radius: .55 (+3) A Atomic radius: 1.72 A Atomic volume: 7.1 cm'/mol First ionisation potential: 7.9024 V

Second ionisation potential: 16.18 V Third ionisation potential: 30.651 V

Oxidation states: 2,(3) Density@ 293 K: 7.86 g/cm'

Specific heat: 0.44 J/gK Heat of vaporisation: 349.60 kJ/mol

Heat of fusion: 13.80 kJ/mol Electrical conductivity: 0.0993 10 •!em ohm

'111cnnal conducti,·ity: 0.802 W/cmK ~lodulus of elasticity: 21110' ~!Pa

Coefficient of thennal exp.: 11.8 I 0 • K' Valence: 2,3,4,6

Ana!ytJCal Method Development

Ana!ytJcal Studies on the Atmospheric Deposltlons

Iron

Element nuclides: Nuclide

Fe 52: 0% Fe 54: 5.82%

Fe 55: 0% Fe 56: 91.66%

Fe 57: 2.19% Fe 58: 0.33%

Fe 59: 0% Fe 60: 0%

ENVIRONMENTAL SIGNIFICANCE OF IRON

Because of its greater abundance in the earth crust, iron is a major component of the

soil, sediment and of water. The dissolution reactions of iron in weathering process

depend on the Eh-pH system of the environment and on the oxidation state of its

compounds. Low pH and redox potential levels favour the ferrous form. On the

contrary, high pH or redox levels create a stable environment for ferric iron. The

electrode potential for Fe(II)/Fe(III) couple is --0.771 V (Bodek et al., 1988).

Aqueous solutions may contain hydrolysed products of Fe(II) or Fe(III) depending

on the pH. Natural waters may contain iron mainly in the complexed form with both

the inorganic and organic ligands. Ferric iron forms stronger complexes with the

organic substances than does the ferrous form. It can also form complexes with

chloride, fluoride, phosphate, and sulphate. Natural stream water could contain iron

as particulate ferric hydroxide or its organic complexes. Of special significance is the

presence in the ferrous form, which could be encountered in oxygen deficient water

such as at the bottom of lakes and rivers. This generates a low Eh leading to the

reduced condition of iron, which may lead to a high concentration of iron in the

water.

As far as the environmental significance is considered iron itself is not toxic, still it

plays a very important role in the cycling of the toxic metals. Iron oxide can absorb

many elements and thus participate in the attenuation of most of the trace and heavy

metals. In non-reducing soils and sediments, the solid iron oxide can absorb a large

amount of trace metals thus exercising a great control on their distribution. In an

aerobic sediment or water system, the metal bonding has been found almost

irreversible. If the oxides are dissolved by reduction, then the absorbed metals may

reappear in the solution or may sometimes precipitate as any other compound such

as sulphide (Kabata-Pendias, 1984). Conversely, b.rge presence of ferrous iron ";n

Analytical studies on th~ AtmosphMc tkposltlons

deplete other complexing ligands, e.g., sulphide thus not providing sufficient amounts

to precipitate other heavy metals (Khalid eta!., 1977).

In wastewater treatment iron and manganese oxides are used as scavengers and thus

retard the harmful effects of the pollutants (Drever, 1982). Similarly, the deep-sea

nodules, which are now considered an important source of many important metals,

could concentrate trace metals viz. Co, Ni, Zn, and Pb due to iron and manganese

oxides only.

A similar effect could be seen on the soils also where trace metals are concentrated

by iron oxide. These metals include Zn, Pb, Mn, Ni, Cu, Co, V, Mo, and Cr. The

absorption is dependent on pH and is greatest for various ions on iron oxide at pH

of 4-5 (Kabata-Pendias, 1984). Thus, it can be seen that determining the iron levels

and its speciation could provide a valuable data to predict the distribution of many

other toxics or trace metals.

BIOLOGICAL SIGNIFICANCE OF THE IRON FOR HUMANS

Iron is an essential element, which is intimately involved in the oxygen transport and

oxygen utilisation in the body. As the oxygen is vital for the various life processes,

iron can also be considered as the most important metal, biologically. Its deficiency in

humans can lead to various disorders viz., anorexia, depressed growth, decreased

resistance to the infections, iron-deficiency anaemia, abnormalities of the gastro­

intestinal tract etc. The symptoms of the deficiency are fatigue, listlessness,

palpitation on exertion, sore tongue angular dysphagia and koilonychia etc. (Oehme,

1973). Iron deficiency is much more common in women than in men as they lose a

large quantity of blood in the fertile cycles, pregnancy and lactation. Haemoglobin

levels of less than 13.5 and 12.5 mg/ dl in men and women respectively are considered

low. The worldwide prevalence of the iron deficiency anaemia in the year 1996 was

1,788,600,000 people and it is ranked as the top most deficiency disorder (WHO,

1997).

The increase m the serum or plasma iron can be brought about by the certain

conditions viz., the increased red cell destruction (t.e., haemolytic anaemia where the

sunival time of the red cell is remarkably decreased), lower utilisation of the iron

(decrea.~ed blood formation in case of lead poisoning), in situations where release of

.lJO

Analytfcal Studies on the Atmosphtt!rlc Depositions

iron occurs (necrotic hepatitis) and in conditions where there is an increased

absorption of the iron take place (e.g., in hemochromatosis, and hemosiderosis)

(Oehme, 1973). A large number of people particularly belonging to the 'Sahu'

community in the Chattisgarh region, are affected by a particular type of 'Sickle Cell

Anaemia.' This disease is attributed to some defective genes and is hereditary in

nature.

INDUSTRIAL SIGNIFICANCE OF THE IRON IN CONDENSER AND BOILER FEED

WATER

The boiler operations hold a place of utmost importance in thermal and nuclear

power plants. The boiler is the device where the water is heated by the energy

obtained by sources such as coal or nuclear reactions and the super-heated steam

obtained is used to operate the turbines for generating the electricity. Thus, boilers

could act as a huge concentrator of the impurities depending on the feed water

quality. These impurities then can lead to the problems viz., a carry-over of the

impurities with the steam, priming, foaming, scales and sludge formation and the

corrosion of boiler walls, turbines, condensers etc. These problems can pose a grave

hazard to the safe and economic operations of the various industries.

Only the effect of metallic impurities will be briefly considered here. The presence of

the metallic impurities in boiler feed water leads to the problem of formation of

internal deposits in the boiler walls. These deposits being the poor conductor of the

heat can lead to the over-heating of the boiler tubes at the spots where such deposits

exceed a certain thickness. In other words, the heat transfer from the fireside through

the tube to the boiler water is reduced at such spots, which becomes over-heated.

Consequently, blisters appear on the boiler tube that may ultimately burst. This type

of problem may also take place with tubes of super-heater and re-heater. The deposit

analysis usually shows the presence of the oxides of Fe, Cu, Ni and Zn that originate

either naturally or from the components bearing these metals in the pre-boiler

section (Venkateswarlu, 1997). Modem boilers of the chemical industries and power

plants operate at high heat transfer rates and posses the evaporation capacities in the

range of 20,000 kg/h. The pressure in the boiler can be 15 kg/ cm2 (Low-pressure

boilers) to more than 64 kg/cm2 (lligh-pressure boilers). Higher is the boiler pressure

more strict is the quality control regime for the feed water quality. Therefore, it is

needed that the feed water may be analysed Ycry correctly at Yery low leYcls to ensure

211

Analytical Studies 011 th~ Atmosph~rlc ~positions

a safe boiler operation. The permissible iron content of the feed water depends on

the boiler pressures etc. and it can range from as high as 10 mg/L to as low as 5

Jlg/L.

METHODS OF THE DETERMINATION OF IRON

Several techniques; polarography (Beyer eta!., 1975; Parry et al., 1973; Kennedy et al.,

1990), spectrophotometry (Bruguera et al., 1984; Senior et al., 1987), photochemical

analysis (Liu et al., 1992) and the X-ray fluorescence spectroscopy (XFS) (Battison et

al., 1993) have been in vogue for the characterisation of iron. Now the atomic

absorption spectrophotometry (AAS) and the inductively coupled plasma- atomic

emission spectrophotometry have become the method of choice in view of their

sensitivity and the selectivity (Cox et al., 1988, Zhu et al., 1988, Dixon et al., 1993,

Zach eta!., 1994, Carrion et al., 1994, Gorm et al., 1994). However, these advance

techniques are not applicable for the field detection and determination of iron and

the availability of the instrument is limited due to the cost factor.

The spectrophotometric approaches are very simple and cheap and are readily

adaptable for the fieldwork. Such methods are based on inter-conversion of one

redox state to another and subsequent complexation with organic, inorganic or both

types of ligands. There are many colorimetric methods but the thiocyanate method

has always been a method of choice as it is cheap, rapid, simple and can be used in

the acid medium. In the presented work, a simple extraction-spectrophotometric

method is described, which is selective and sensitive for the determination of iron.

The proposed method modifies the thiocyanate method to make it even more

sensitive and selective. The presented method is fully adaptable for the field

application and has been successfully used for many such applications. Examples are

the determination and speciation of the iron in groundwater of the Rajnandgaon

district of 1\fll, in the atmospheric particulate and the rainwater of Bhilai city and in

the boiler feed water of a steel industry at Raipur.

In the method, the iron(III) is complexed with thiocyanate ions in the presence of a

cationic surfactant, cetylpyridinium chloride (CPq and an anionic surfactant, Triton­

X-100 (Tx-100) and is subsequently extracted in organic solvents. ll1e complexation

wtth the thiocyanate in the presence of the surfactants greatly enhances the scnsiti,;ty

}I]

of the plain thiocyanate complex and its extraction in the organic phase helps in

furthering the sensitivity and the selectivity.

3. EXPERIMENTAL

Apparatus

A Sicco-Feedback (Digispec-110 D) matched with 1-cm quartz cells was used for the

spectrophotometric determination. A GBC make atomic absorption

spectrophotometer (902BC) was employed for the calculation of the percentage

extraction and comparison of the data. Systronics make pH-meter type MK-VI was

used to measure the pH of solution.

Reagents

All reagents used in this experiment were of analytical grade (E. Merck). The standard

solution of iron was prepared by digesting pure iron wire with acids, and by

dissolving the residue in 1 Lit of double distilled de-ionised water. Other solutions

used were: 3.4x1o-J,potassium dichromate, 2.8 x 10-~CPC and 4.0 M solution of

ammonium thiocyanate and, 1.8 x 10 -~solution of Tx-100. The 5 M HCl was used

for acidity or pH adjustment of the solution. De-ionised and double distilled water

was used for the solution preparation.

Procedure of the determination

An aliquot of the standard iron solution containing up-to 10 j..lg iron was placed in a

100-ml separatory funnel. It was then mixed with 0.1-ml K2Cr,07, 1.5-ml HCl, 2.0-ml

NH,SCN, 0.5-ml CPC, and 0.1-ml Tx-100 and was diluted to 30-ml with distilled

water. The aqueous phase was extracted with 5-ml chloroform and washed with a

1x2-ml portion of chloroform. The extract was dried over anhydrous sodium

sulphate (2g). Volume of the combined extract was made up to 10 ml in a volumetric

tlask_ A blank was run in the same manner excepting the addition of iron.

Absorbance of the sample extract was measured against a blank at the wavelength of

500 nm_

AIM/ytlc31 Studies on the Atmospheric Depositions

Determination of the percentage extraction

Determination of the percentage extraction is a convenient way to fmd out the

completeness of the extraction. Use of atomic absorption spectrophotometry (AAS)

was made here to fmd out the percentage extraction as it provides very accurate

results. General procedure for this determination was that a 30-ml solution

containing up-to 10 ].lg iron was extracted, explained as above. Extracted organic

phase was then evaporated and the residue was carefully taken into 10-ml dilute

hydrochloric acid (0.1 M). The iron content in this was determined by the ASS at the

instrumental parameters described in Table 2.

Table 2. Instrumental parameters employed in AAS determinations

Parameter Wavelength

Spectral band-width Lamp current

Flame composition Flame stoichiometry

Sensitivity Detection limit

Value 248.3nm 0.2 nm SmA

Air-acetylene Oxidising

0.045 ].lg/ml 0.006 ).lg/ml

Sample collection for the application and its preparation

Rainwater was collected in the rainy season on episodic basis. Samples collected were

filtered through a Millipore filter paper (0.5 J.l.m size). Treated boiler feed water was

obtained from the NECO Steel Plant, Raipur .. For groundwater analysis, the freshly

pumped water was filtered through the Whatman (40) filter paper and the filtrate was

used as such.

4. RESULTS AND DISCUSSION

CHEMISTRY OF THE THIOCYANATE COMLEXATION

Seven metals: iron(III), cobalt, uranium(VI), niobium(\'), molybdenum(\\

tungsten(\') and rhenium form complexes \\ith the thiocyanate coloured enough to

be determined spectrophotometrically. For iron determination the thiocyanate

Analytical StUdll$ on th~ Atmosph~rlc D~posltions

method is attractive as the determinations can be carried out even in the strongly

acidic solution with good sensitivity. It is because the thiocyanic acid is highly ionised.

Nevertheless, the selectivity of the method is low because of its reactions with the

above-mentioned metals, if present and other probable elements viz. titanium,

ruthenium, osmium, iridium and bismuth. Generally, the thiocyanate forms a series of

consecutive complexes wherein the absorption peaks are shifted to longer

wavelengths with the increasing thiocyanate concentrations but the exact

compositions are still not very clear (Sandel, 1959, Home, 1978). A maJor

shortcoming in the thiocyanate chemistry is the instability of the coloured solutions

that may be caused by the reducing property of the thiocyanates, its decomposition

products causing the fading of the Fe(III)-cyanate complex or by the slow

decomposition of the thiocyanate in acidic medium. The decomposition caused

essentially by the polymerisation of the thiocyanic acid results in the formation of

yellow coloured products (Sandel, 1959) and is the main cause of the colour

instability. The use of acetone to improve the colour constancy and the intensity was

extensively studied (Crouthamel et al., 1952, 54). Still, there are many drawbacks

associated, such as the increased interference and the volume limitations. Thus, need

to increase the selectivity and the stability of the iron -thiocyanate complex for

determining the trace quantities of iron in various type of samples, is evident. This

can be done by an understanding of the Fe(III)-thiocyanate chemistry and suitable

modifications to it.

This study has attempted to address the aforesaid issues and to make the method

applicable for the field determination of iron. The iron(III)-thiocyanate complex can

not be extracted into non-polar solvents, which is desirable to minimise the

interferences associated with the use of polar solvents. Such an extraction in a non­

polar solvent can be achieved by adding a reagent or a mixture of such reagents that

can act as the counter ions or the adducts, to cause the extraction. In the paper

communicated for publication (Pandey, Chandrawanshi, Patel, 1997) the use of a two

pronged strategy had been proposed. First is the use of a cationic surfactant in

conjunction with amides and the second is the use of a mixture of cationic and

anionic surfactant for the extraction of iron. Both methods prO\;de good extraction

efficiency over a wide range of acidity with increased scnsiti,;ty. Part of the work

concerning the surfactant-amide usage has been presented in a Ph.D. thesis

(Chandrawanshi, 1997). This chapter reports here the usc of the surfactant mixtures

]JS

Analytical Stud/a on the Atmospheric Depositions

for the extraction of iron and the chemistry involved in these extraction methods is

elucidated. The absorption spectra of Fe(III)-SCN-CPC-Tx-100 and Fe(III)-SCN­

CTAB-OAA complex against the relevant regent blank is shown in Figure 1. These

complexes exhibit an absorption maximum around 480-500 nm with a negligible

absorption by the respective reagent blanks (Fig. 1). A bathochromic shift of"' 20-40

nm takes place in the formation of these complexes. Values of molar absorptivity of

the complexes in organic solvents viz. chloroform or toluene lies in the range of (1.2-

3.5) x 104 at their respective absorption maxima as shown in the Table-3.

Spectral study of the complexes

0.5.------

Q) 0

0.4

ai 0.3

-e 0 .2 0.2 <(

I

--0.1-rs:--0 - ' :::::~~~\":=;'~~~~--~-=--~~

400 460 520

Wavelength nm

-e- A -e-- B -e- C ....,._ D __.,._. E

Figure 1. Absorption spectra of the complexes

[Fe(III)] ='7~ g/10 ml, in respective extractant used l To~ l1~ ml·)

[HCl] = 0.25MforA&DandO.l MforB,C,E

[NH.SCN] "' 0.27 M

(A) Fe(lll)- SCN-CPC-Tx-100 complex.

(B) Fe(lll) -SCN-CPC-OAA complex.

(C) Fe(lll) -SCN-CTAB-OAA complex.

(D) SCN-CPC-Tx-100 reagent blank

(E) SCN- CTAB -OAA reagent blank as in tbe procedure.

600

}16

Ana/ytlal studies on th~ Atmospheric Depositions

Table 3. Spectral data of the complexes studied.

Surfactant Reagent Absorption Molar Extractant used Maxima Absorptivity

nm L mole ·1

cm-1

CTAB N-Phenylacetamide 480 22,000 Toluene

CTAB N-Butylacetamide 480 24,200 Toluene

CTAB N-Pentylacetamide 480 24,200 Toluene

CTAB N-Hexylacetamide 480 24,200 Toluene

CTAB N -Octylacetamide 480 24,200 Toluene

CPC N -Octylacetamide 480 26,000 Toluene

CPC Tx-100 500 35,000 Chloroform

Extraction efficiencies of some selected complexes are shown in the following table

(Table 4). These data show an increase in the extraction efficiency with the addition

of the reagents capable to act as adducts. High extraction efficiencies (>99%) could

be achieved using the surfactant mixtures or the surfactant and amide mixture.

Table 4. Extraction efficiencies of the iron(III) complexes with thiocyanate, amides and surfactants

Reagent

SCN-

SCN-+ OAA

SCN-+ CTAB

SCN- + CTAB + OAA

SCN- + CPC + OAA

SC'-.1· + CPC

SOH CPC + Tx-100

0.\A N-ocl)lacNamzde, CTAB 100 = tnton-x-100

Percentage Absorption Molar Solvent extraction maxtma absorptivity

%E ;\.max E

nm L mole -1 em·' Nil - - Toluene,

chloroform

51.3 480 12,500 Toluene

82.9 480 20,200 Toluene

99.0 480 24,000 Toluene

99.4 480 26,000 Toluene

85.0 490 23,800 Chloroform

99.8 500 35,000 01loroform

uryl tnmethJI ammoruum brorrud<". CPC- uryJ rrndinmm chlonde. Tx-

)17

Analytical Studies on the Af:mosph~rlc ~positions

OPTIMISATION OF THE ANALYTICAL PARAMETERS FOR THE DETERMINATION OF

IRON(III)-THIOCYANATE-CPC-TX-1 00 METHOD

Effect of the extracting solvent

Various water immiscible organic solvents were tested for their efficacy of extraction

of the complex. Organic solvents were found to increase the colour intensity and the

stability. The complex is quantitatively extracted in the benzene, toluene, chloroform,

1-pentanol, methyl isobutyl ketone (MIBK) and ethyl acetate. The molar absorptivity

of the complex in various solvents lies between (2.42 - 3.5) x 104-l mole _, em·' at

respective absorption maxima (Table 5). Evidently, the chloroform is the best solvent

to offer the maximum colour strength and low toxicity.

Table 5. Effect of the organic solvent on the extraction

[KzCrt:O,] = 1.13 x 10-5M

[HCI] = 0.25 M

[CPq = 4.6 X 10 -4 M

[NH,SCN]= 0.27 M

[fx-100] = 6.0 x 10 -5

Solvent Absorption maxima Molar absorptivity A max E

nm L mole -t cur'

Benzene 490 34,900

Toluene 500 34,800

Chloroform 500 35,000

Ethyl acetate 500 25,000

1-pentanol 490 29,000

MIBK 500 24,200

Effect of the acidity

The effects of acid VIZ., hydrochloric acid, sulphuric acid and nitric acid were

examined. The sulphuric acid reduces the colour intensity as expected. Nitric acid

provided good colour development but was less stable. Hydrochloric acid was found

more suitable. Acidity of the solution does not affect much the colour strength of tl1e

Fe(III)-thiocyanate complex. The normal stable range is the 0.05 ~I to 0.8 M acidity

in the solution. However, the range of acidity is a little narrower, whereYer the

.218

Analytical studies on the Atmospheric Depositions

surfactants are involved in the chemical reactions. This happens probably because the

effect of the acidity on the ionisation and the attainment of the critical micellar

concentration (C.M.C.) of the surfactants. In the present method, the optimum range

of hydrochloric acid is 0.15 M to 0.35 M (Table 6). Based on that the optimum acidity

value of 0.25 ± O.OlM HCl was maintained for other experiments.

Table 6. Effect of acidity on the extraction of the Fe(III)- SCN-­CPC- Tx-100 complex

[K2CrL07

] = 1.13 x 10 _, f'l] [V org: V aq] = 1:3

[Fe]

[CPC]

= 7.0 f!g in 30-ml aqueous phase

= 4.6 X 10-4M

[NH.SCN]= 0.27 M

[fx-100] = 6.0 x 10 -5

Concentration of the f(ydroch!oric acid Absorbance at 500 nm in aqueous phase

M 0.10 0.378

0.15 0.438

0.20 0.435

0.25 0.440

0.30 0.439

0.35 0.438

0.40 0.400

Effect of the ammonium thiocyanate

A relative excess of the thiocyanate ions is desirable in the iron-thiocyanate reactions.

As it increases the sensitivity, colour intensity and reduces the errors caused by the

presence of chlorides, phosphates and other such ions capable to form complexes

with the ferric iron in the acidic medium. This has been found applicable to the

present method also.' A minimum concentration of the 0.06-l\l thiocyanate was

necessary for the complete colour development and the further addition unto 1.5-:\l

had no adverse effect (Table 7). \"\'orking concentration adopted was 0.25-:\1

thiocyanate.

AndlytJca/ Method lJeo.elopment 219

Analytical Stud!~ on th~ Almospht!tlc ~positions

Table 7. Effect of the concentration of ammonium thiocyanate on the extraction of the complex

[K,Crz07] = 1.13 x 10 -sM

[Fe]

[CPC]

= 7.0 ~gin 30-ml aqueous phase

= 4.6 X 10-4M

Concentration of the ammonium thiocyanate in aqueous phase

M 0.04

0.06

0.08

0.10

0.20

0.40

0.60

1.0

1.5

2.0

Effect of the surfactants

A. Effect of the natUie and type of the surfactants

[V org: Vag]= 1:3

[HO]= 0.25M

[Tx-100] = 6.0 x 10 -s

Absorbance at 500 nm

0.349

0.439

0.439

0.438

0.440

0.440

0.444

0.445

0.439

0.395

In this method, the surfactants govern the process of the complex formation, colour

intensity, extraction efficiency and other analytical parameters. A surfactant is made

of a strongly hydrophobic group and a strongly hydrophilic group combined in a

single molecule. The surfactants' hydrophobic group is generally a hydrocarbon

radical (R) containing 10 to 20 atoms. The hydrophilic group can be either ionic or ',- - '

non-ionic in nature th~s, making the surfactant an ionic surfactant or a non-ionic

surfactant. Ionic surfactants, thus, can be of two types: cationic or anionic depending ,·· '

on the charge on the surfactant body on ionisation. To study the effect of the

surfactant all three major type of surfactants namely the cationic, anionic and non­

ionic were tested. Among these surfactants, the cationic surfactants play a decisi\·e

Analytical Stud/~ on the Atmospheric Depositions

role in the chemistry of colour formation and extraction and the reactions are

influenced by the non-ionic surfactants. Table 8, presents the effect of the types of

surfactan ts.

Table 8. Effect of the type of surfactant on the extraction of the complex

[K,Crz.O,] = 1.13 X 10 -S M [V org: V aq] = 1:3

[HCI] = 0.25 M [NH,SCN]= 0.27 M

[Surfactant] = 4.6 x 10-4M

Surfactant

Brij-35

SLS

Tx-100

Tx-300

CTAB

CPC

Nature

Anionic

Anionic

Non-ionic

Non-ionic

Cationic-·

Cationic

Absotption maxima Molar absotptitity

A-max E

nm L mole - 1 cnr1

No extraction

No extraction

500 18,300

500 17,000

500 20,200

500 23,800

SLS= sodium Iaury! sulphate, Tx-100 =Triton x-100, Tx-300 = Triton-x-300, CPC =cetyl pyridiniurn chloride, CT AB = Cetyl trimethyl ammonium bromide

Based on above, the CPC and the Tx-100 were chosen for the further investigations

as both of them have shown the maximum molar absorptivity and thus, the

extraction efficiency among their respective class.

B. Effect of the cetylpyridinium chloride

Cetyl pyridinium chloride (CPq has been found effective over a range of 3.5 x I 0 · 4

;'II to 6.0 x 10 -4

M concentration (fable 9). The final CPC concentration used for

the rest of the experiments was 4.6 x 10 -.• J\1.

221

AnHiytlcal Studies on th~ AtmosphMc Depositions

Table 9. Effect of the concentration of CPC on the extraction of the complex

[K,Cn:O,] = 1.13 X 10-5 1\']

IFeJ = 7.0 f(g in 30-ml aqueous phase

[HCl] = 0.25 M

Concentration of cetylpyridinium Chloride in aqueous phase

Mx 10·4

3.0

3.5

4.0

4.5

5.0

5.5

6.0

6.5

C. Effectofthe Tx-100

[V org: V aq] = 1:3

[NH,SCN]== 0.27 M

[Tx-100] = 6.0 x 10 ·5

Absorbance at 500 nm

0.415

0.434

0.442

0.440

0.440

0.438

0.440

0.420

The anionic surfactant Triton-X (Tx-100) has been found effective from a

concentration of0.4 x 10 ·• M to over 6.0 x 10 -• M concentration. The final Tx-100

concentration used for the rest of the experiments was 6 x 10 -s M (Table 10).

Table 10. Effect ofTx-100 concentration on the extraction ofthe complex

Analytical Studies on the Atmospheric ~positions

Table 10. Effect ofTx-100 concentration on the extraction of the complex

[K2CaO,] = 1.13 x 10 -s M

[Fe]

[CPC]

= 7.0 flg in 30-ml aqueous phase

= 4.6 X 10-4M

Concentration ofTx-100 in aqueous phase M X 10-•

0.3

0.4

0.6

0.8

1.0

3.0

6.0

Effect of the dilution

[V org: V aq] = 1:3

[NH.SCN]= 0.27 M

[HCI] = 0.25 M

Absorbance at 500 nm

0.378

0.435

0.440

0.442

0.440

0.441

0.440

Effect of the dilution, that is the ratio of organic phase to that of the aqueous phase

was studied by taking 1 0-ml chloroform or toluene as organic phase and varying the

volume of the aqueous phase. It was observed that stable readings could be obtained

if the ratio V-organic : V-aqueous was at-least 1:2. This phenomenon can be

explained on the basis of the critical micellar concentration (c.m.c.) concept wherein

the surface active ions associate at certain concentration to form the larger units

(micelles) responsible for the surfactant action (Tadros, 1989). Instability of the

colour was observed when 1:1 to 1:2-ratio between the organic phase and the

aqueous phase was maintained. This explains that the c.m.c. value of the surfactant

mtxes used could not be achieved if the V org :V aq was less than 1:2 or more than

1:4 (fable 11). The fmal ratio used for experiments was 1:3 (V org: V aq).

Analytict~lstudles on th~ Atmospheric Depositions

Table 11. Study of the effect of dilution on the extraction of the complex

[KzCrL07] = 1.13 x 10 -5 M

[Fe]

[CPC]

= 7.0 Jlg in 30-ml aqueous phase

= 4.6 X 10-4M

Volume ratio of organic to aqueous phase

1:1

1:2

1:3

1:4

1:5

Effect of the temperature

[HCI] = 0.25 M

[NH.SCN]= 0.27 M

[Tx-100] = 6.0 x 10 -5

Absorbance at 500 nm

0.390

0.433

0.440

0.440

0.361

Temperature affects the colour intensity and the stability of the ferric thiocyanate

solutions and a decrease of about 7% has been reported (Sandel, 1959) when the

temperature is raised from 15° to 30° C. The rate of fading is greater at higher

temperature. The present method too is subject to the effects of the temperature and

it affects the reproducibility and the molar absorptivity of the complex, particularly

when only a mixture of the surfactant was used. The Kraft temperature of the

surfactants probably governs this wherein the temperature affects the process of

attainment of the critical micellar concentration (Tadros, 1989). The results were

reproducible between 20-25°C, which is the normal temperature. Therefore, the

experimental work was carried at room temperatures (23 ± 2°C).

Calibration Curve and Correlation Coefficient for the Detennination of lron(/11) with

Thiocyanate, CetylPyridinium Chloride and Triton·X

The calibration curve was plotted by taking standard Fe(III) solution containing 0.1

to 1.0 !lg iron(Ill) per ml of organic phase (1-10 !lg/per 10 mQ corresponding to

about 33.33, I 00.00, 200.00, 233.33, 266.66, 300.00, and 333.33 ppb of iron in 30-ml

water and was extracted as in the procedure. The Beer's law is followed from 0.0 to

1.0 llg/pcr ml of organic phase (0-10 !lg/per 10 mQ. The regression statistics (I'able

13) show a high R-square ,-alue (0.994). The line fit plot of the iron concentration

Anil/yt/cill studies on the Atmospheric Depositions

and its absorbance (Fig. 3) and the calibration curve with probable variations

corresponding to the standard error (Fig. 4) show a good agreement between the

values obtained.

[Fe]

[CPC]

[HCI]

Table 12. Calibration cnrve and the correlation data for the determination of iron

= 7.0 f.1g in 30-ml aqueous phase

= 4.6x 10-4M

= 0.25M

[V org: V aq] = 1:3

[NH,SCN]= 0.27 M

[Tx-100] = 6.0 x 10 .s

Concentration of Iron(III) Absorbance at 500 run Correlation

J.lg/per ml of organic phase Coefficient

0.1 0.070

0.3 0.190

0.6 0.370

0.998 0.7 0.440

0.8 0.500

0.9 0.550

1.0 0.600

1.1 0.630

Table 13. Regression study on the calibration data

Analytical Studt~ on th~ Atmosph~rlc CMposltions

Table 13. Regression study on the calibration data

Multiple R

R Square

Adjusted R Square

Standard Error

Observations

Regression statistics

0.997

0.995

0.994

O.DlS

8

Calibration Curve for the Iron Determination

0 0.3 0.6 0.9

Concentration of Fe(IIQ micr<H}ramhn/ of organic phase

• Absorbance at 500 nm -Linear (Absorbance at 500 nm)

Fig. 2. Calibration curve of the iron complex

1.2

"' " E c c .2 0 6 0

"' ~ -"'

Calibration curve of Iron Determination Line Fit Plot

0.8

r ~

_ _; -.2·"'": 0.6 .. -;',· ..

0.4 ,, '': _',.;/

·--<~:.

0.2

__ ,,,

C, • i ·, ... . 0 --, I . I

0 0.5 1 1.5

Concentration of Iron (Ill) per ml of organic phase

• Absorbance at 500 nm • Predicted Absorbance at 500 nm

Fig. 3. A line fit plot of the iron concentration and its absorbance

0

Calibration Curve for the Tron Determination talcing the standard error as probable deviation

0.3 0.6 0.9

Concentration of Fe(lll) mlcro-gramlml of organic phase

• Absorbance at 500 nm --Linear (Absorbance at 600 nm)

1.2

Fig. 4. Probable variation in the observed absorbance corresponding to the standard error

lll

Anil/yt/~11 studies on th~ Atmosph~rlc ~positions

The detection limit, precision and sensitivity of the method

The precision of the method was determined by extracting 7.0 ~g of iron(III) present

in 30-ml of aqueous solution into 1 0-ml of chloroform as given in the procedure. The

standard deviation at the optimum conditions was low (0.0028) with a range of 0.440

± 0.01 (Table 14). The detection limit (causing more absorbance than twice of the

standard deviation) was 4-ppb iron in aqueous solution.

[Fe]

[CPC]

[HCl]

Table 14. Precision of the method

= 7.0 Jlg in 30-ml aqueous phase

= 4.6 X 10-4M

= 0.25M

Parameter

Mean

Standatd Error

Median

Mode

Standard Deviation

Variance

Kurtosis

Skewness

Range

Minimum

Maximum

Sum

Count

Confidence Level(0.950000)

Value

0.441

0.002

0.440

0.440

0.006

0.00004

0.553

-0.501

0.021

0.429

0.450

4.407

10

0.004

IV org: V aq] = 1:3

[NH..SCN]= 0.27 M

[fx-100] = 6.0 x 10 ·S

COMPOSITION OF THE COMPLEX

Iron(III) can form a variety of complexes depending on the number of the

thiocyanate ions co-ordinated with the Fe(III). This can be depicted as:

Fe>+ + n sew~ [Fe (SCN)n )'' -n

Where the value of n could be 1 ... 6. At low thiocyanate ion concentrations iron(III)

forms [Fe (SCN)J 2+ predominantly (Lewin et a!, 1955). At 0.1 M concentration of

thiocyanate the resulting complex is mainly [Fe (CNS),f. It is predicted that above

0.2 M concentration of thiocyanate, negatively charged complexes may predominate.

However, the lower log K values prevented the formation of a stable complex. The

approximate log K'. values were reported as 2.3, 1.94, 1.4, 0.8, and 0.02 for n = 1. ..

5, respectively (Babko, 1946). In the present investigation, the thiocyanate

concentration was 0.27 M, which should favour the formation of negatively charged

iron(III)-thiocyanate complex. Further, as the stability of the complex is good it can

be presumed that the cationic surfactants added in the solution stabilise the complex.

The anionic surfactant or amides help in the quantitative extraction of the complex

leading to higher extraction efficiency and the molar absorptivity.

To verify the above by fmding out the composition of the complex, methods such as

the mole ratio, slope ratio, Job's ratio of continuous variation and the curve-fitting

were tested and the curve fitting method (Sillen, 1956) was found applicable. For this

7.0 !lg of iron solution was extracted as described in the procedure and the log

distribution ratio [Log D) of the metal was plotted against the log molar

concentration [Log M] of the reagent. The distribution ratio [OJ was calculated by

the formula:

[D) =A eq I (A max- A eq)

Where A eq is the absorbance of the complex when the reagent is in equilibrium and

A max is the absorbance of the complex when the reagent is in constant excess.

Table 15, presents the data on the pog M) and pog D) and the figure (Fig. 5) shows

the regression between the data set.

Table 15. Curve fitting method for the determination of the molar ratio of Fe(III)- to thiocyanate in Fe (Ill)- SCN·- CP• - Tx-

100 Complex in chloroform

Ana/ytJcaJ Method I:Jewjopment

Analytical Studies on the Atmospheric Depositions

Table 15. Curve fitting method for the determination of the molar ratio of Fe(III)- to thiocyanate in Fe(lll)- SCN-- CP+- Tx-

100 Complex in chloroform

[KzCrL07] = 1.13 x 10 -5 M [V org: V aq] = 1:3

[NH.SCN]= 0.27 M

[Tx-100] = 6.0 x 10 -5

[Fe] = 7.0 /-Lg in 30-ml aqueous phase

[CPC]

[HCl]

= 4.6 X 10-4M

= 0.25M

Concentration of ammonium Distribution ratio of the thiocyanate in the aqueous metal between the

c g 0 c

.§'

phase organic and the aqueous phase

M X 10 _, LogMNH4SCN D LogD

4.8 -2.316 0.101 -0.999

5.26 -2.279 0.255 -0.595

6.14 -2.212 0.580 -0.2364

7 -2.154 1.012 -0.005

Molar Ratio of Iron to Thiocyanate

-2.35 -21

,---------------------.- 0.2 -2.3 -2.25 -2.2 -2.15

f-----~~~-~~~~~~~~---}0

-0.2

Slope= 5.92 -0.4

-0.6

-0.8

Log M Thiocyanate

Fig. 5. Curve fitting method Cor the determination oC molar ratio of the iron to thiocyanate in the complex

Analytical studies on the Atmospheric Depositions

Table 16. Summary regression statistics of the regression between the log M and log D values .of the complex formation

Parameters Value

Multiple R 0.979

R Square 0.959

Adjusted R Square 0.938

Standard Error 0.108

Observations 4

Log M and log D values for the thiocyanate and iron complex is well-correlated (R

square value 0.959, Table 16). Based on the study the involvement of six thiocyanate

ions to one Fe'+ can be deduced on the basis of a slope of"" 6 (5.92 actual) between

the log M and log D values of the thiocyanate and the metal. Similarly, a slope of"" 3

(Table 17, Fig. 6) was deduced between that of the CPC ions and the metal. This

method could not deduce the molar ratio of the adduct Tx-100.

Table 17. Curve fitting method for the determination of molar ratio of Fe(III)- to CPC in Fe(III)- SCN-- CP+- Tx-100 complex in

chloroform

[KzCr:.O,] = 1.13 x 10-5 M

[Fe)

[CPC]

[HCl]

= 7.0 ftg in 30-ml aqueous phase

= 4.6 X 10-4M

[V org: V aq) = 1:3

[NH.SCN]= 0.27 M

[fx-100) = 6.0 x 10 -5

= 0.25M

Concentration of CPC in the aqueous Distribution ratio of iron between phase the organic and the aqueous phase

Mx 10-5 LogM D LogD

6.309 -4.200 0.232 -0.634

7.943 -4.100 0.477 -0.322

8.810 -4.050 0.692 -0.160

9.772 -·t.010 0.803 -0.095

EI

AnH/ytJCHI studies on the Atmospheric ~positions

Molar Ratio of Iron to CPC in the Co~lex

-4.250 -4.200 -4.150 -4.100 -4.050 -4.000

0.000 c e Slope= 2.92 -0.200

-0.400 '0 0

-0.600 "' ..9 -0.800

Log M CPC

I • Log D - Unear (Log D) I

Fig. 6. Curve fitting method for the determination of molar ratio of the iron to thiocyanate in the complex

Similar study for Fe(Ill)-SCN-CPC-OAA complex (Chndrawanshi, 1997; Pandey et

aL, 1997) showed the involvement of 4 SeN· and 1 CTAB or CPC molecule to each

Fe,. molecule to give a red-orange coloured neutral complex extractable into toluene.

The molar ratio of the N-donor organic reagent (amide) could not be determined.

Another previous study in our lab (Patel, 1979; Patel et al., 1979) using the hydroxy­

amidine reagent (HOA) had showed the involvement of one molecule of hydroxy­

amidine to one molecule of the Fe(III)-SCN complex.

From the above observations the following reaction mechanism could be established:

•!• { 1} Formation of iron-thiocyanate complex

Fe-'+ + n St N- +-t [Fe (SC::-..j. ) 3+- 0

•!• { 2} At =o.t i\1 concentration of thiocyanate in the solution and the presence

of the hydroxy-amidine reagent (I lOA)

Analytical studies on the Atmospheric Depositions

Fe'++ 2 SCN- + HOA ++ [Fe(SCN), .OAJ + JI+

•:• {3}. At :=0.15- <0.2 M concentration of thiocyanate in the solution and the

presence of a cationic surfactant (CPC)

FeH + 4SCN- + CPC ++ [Fe (SCN).- . CP+J + 0.

•:• ( 4} At >0.2 M concentration of thiocyanate and the presence of the CPC a

cationic surfactant

Fe'+ + 6 SCN- + 3 CPC ++ [ Fe(SCN)o3 .. 3 CP+J + 3 Cr

•:• { 5}. Extraction of the complexes in the organic solvents

Obviously, the iron-thiocyanate-amidine complex is easily extractable in organic

solvents. In case of the iron-thiocyanate-surfactant complex, the presence of '

an adduct viz. the amides or the Tx-100 enhances the extractability by the

formation of the following:

[Fe(SCN)n 3+-n. x CP+J + yAo ++ [Fe(SCN)n 3+-n. x CP+J.yAo

Where 'SCN' denotes the thiocyanate, 'CP+' denotes the cetyl pyridinium cation,

'A' denotes the adduct (amide or Tx-100) and 'o' denotes the organic phase.

The value of n can be 4-6, x can be 1-3 and the y is indeterminate.

The above reaction mechanism is theoretically sound and is supported by the

practical evidences and thus beautifully explains the chemistry of the iron(III)

determinations by thiocyanate method involving the surfactants or other organic

reagents.

Effect of the foreign ions.

Fe(III) was extracted by the procedure as described earlier, in the presence of a large

number of foreign ions and their tolerance by the method was determined (fable

18). The tolerance limit was set until which an error of less than 3% was observed.

Ions commonly associated with iron in the natural waters were tolerable in the

method. Presence of the reducing agents viz. tin chloride, ascorbic acid oxalic acid

etc. obviously interfered with the iron determination by com·erting the Fe(Ill) into

the Fe(ll). However, that can be overcome adding a few drops of concentrated nitric

acid.

m

Analytical studies on the Atmospheric Depositions

Table 18. Effect of the foreign ions on the determination of iron

[I<zCuO,J = 1.13 x 10-5 M

[Fe] = 7.0 J.Lg in 30-ml aqueous phase

[CPC]

[HCI]

= 4.6 X 10-4M

= 0.25M

Foreign Ion Added as AI (Ill) Al(N0,)3 9H,o

As(V) NaHAsO,

Be (II) BeS0,.4HzO

Bi (Ill) Biz(SO,),

Br- NaBr.2HzO

Cd (II) CdSO,. BH,O

Ce(IV) 2(NH,)zSO,.Ce(SO,)z. 2Hz0

CH,COO- CH,COONa

Citrate Na,C,H50,.2H,O

Co (II) CoSO,. 7H,O

Cr (Ill) Cr,(SO,)<; AJ,(S0,)_.24 H20

Cr (VI) KzCrz07.

Cu (Il) CuSO,. 7H20

EDTA NazEDTA

p- NaF

Ga(IIJ) GaO,

Hg (Il) HgClz

I- KI

In (Ill) In Cia

Mn (II) MnOz.4fi,O

.Mo (VI) (NH,)oMo,0,..4!I,O

Ni (II) NiSO,. 6H,O

Pb (II) Pb (NO,),

PO,--- Na,P0d2H,O

Sb (V) Kd!,Sb,O,. 41 [,0

(V org: V aq] = 1:3

[NH,SCN]= 0.27 M

[fx-100] = 6.0 x 10 -5

Tolerance Limit, EEm 100

100

100

40

500

10

500

500

so' 5

100

1,000

5

100

500

40

10

500

so 50

5

100

200

500

50

Af71/ytJC~I studle~ on t/1(! Atrnosph~rlc f)(!posltlons

Sc (IV) NaScO, 200

So (N.) SnCJ, 100

Tartrate NaKC,JI,O,. 4H,O 500

Ti (li) K,TiO (C,0,).2. 2H,O 10

Tl (III) TICh 5

V(V) NH.VO, 40

W(VI) Na,wo,.2H,O 5

Zn (II) ZoSO,. 7H,O 5

Zr (IV) ZrOCJ,. 8H,O 200

T olenmce Limit [Causing erro:r less than 3%]

Based on the above the interferences likely to be encountered in the environmental

applications are minimal.

5. COMPARISON OF THE METHOD WITH OTHER REPORTED METHODS

Some reported methods for the iron determination have been compared (Table 19).

This comparison shows that the most methods suffer from either poor selectivity or

sensitivity or both. Thus, there exists a good scope of development of a

spectrophotometric technique. Some modification has been reported in thiocyanate

method using amines and a surfactant (Hyashi et al., 1986). To enable the easy

characterisation of iron with increased sensitivity as described above is useful for the

field detection of iron at ppb levels in various environmental and industrial samples.

PTO

Table 19. Comparison of the major methods of iron determination

Analytlal5t1ldles on the Atmospheric Depositions

Method

Table 19. Comparison oftlie major methods of iron . · determination

Solvent pH/ Addity

A,....., €!

nm Lmo!e-' em-'

Remarks/ lnterfennce

Reference

----·- -----------· ·- ------- ------- ------- f-----~----:- -----

2,2-Diperidyl (ketone)2

benzothiozol hvdrazone

Aqueous '

.. 45.5-8.5 ' ..

427 34,100 Cd, Pd, Cr, Zn, Ni

2-(2- Aqueous 9.0. 630 122,000 j Various ions Benzothiazolyiazoly I interfere

Siogh et a!., 1983

Qiu eta!., 1986

1

: iazo)-catechol + / I

'T10-p~~~~~rol~"f/, -Aq~~ou5;-3.0-5.0TSi2"1o,600 l -~ sensiti~iti,-+-H:oshi et 'I I j mterference ofi- j aL, 1986

I, .

1

_ . . .. : s-, EDT A, 1 : 1 · i oxalate, etc.

I 1-Phenyl-3- I Aqueous ! 5.5 " 410 ./200,000 1 Cu, Mo, Cd, Bi, ,1• Dyas eta!.,

thiobenzoyl-2- I · j · - ' ' Ag, and Zn , 1983 I thiourea I · i 1 interfere i

I' 2-(4,5-Dimethyl1- Chlorof 1 5.8 773 13,800 ! Long standing II Sanchez et

2-thiazolyazo)-4-,6- orm 'I ~- j time (>40 min) a!., 1988

I' dimethylphenol

1 for the colour j

I .. i development

r 2, 4- Aqueous I 5.5 ' 410 . 200,000 ! Cu, Mo, Cd, Bi, 1 Dihydroxybenwph I I I Ag, and Zn 1 enone + , · interfere [ semicarbazone . i I · , . .. i

Alizarin red-S I ?;::r / 5.2-6.2 . ~70 34,800 1 various ions

Interference by

1 Cyclohexan-1, 2, 3-l' Dimethy.. 2.25 M 570 16,500 T tcione-1, 3-dioxime- . !formam HO ' interference

-2- ide '( ,, I thiosemicarbazone

Di-2-pyridylmethanone-2-pvridvlhvdrazone Mocin+Nemol-K-

1030

Salis aldehyde

Thiocyanate

Dioxane 1.5-2.6

Aqueous 3.7

Aqueous 5.0

Aqueous 0.6-2.5

540

417

440

480

i '

14,000 !

I Cu, Co, Hg, In, V,Pband Zn

interfere 63,300 I I -AI, Zc, Ti, V

! 5,190 Interference Ti,

Sb, Cr, C..d, Ag, PO, ---, C,O,-

8,300 l Low sensi!Wity, ' narrow r:u•gc of

nriabt,.,., high , interferences

llyas and Joshi, 1983

Prezeszlak owski

Yan et al, 1993

Otomoet al., 1991

Hemande Z Ct aJ., 1986

Tonkovic et a!., 1985

Sandel, 1959

-

'

AM/ytiCHI stvdJes 011 th~ Atmosph~rlc Depositions

Metbod .. ' Solvent pH/ llu.x t Rtmarks/ Reference Acidity nm Lmole- Interference

' '' 1 cnr1 ' '- ,- : )

Thiocyanate + cetyl Chlorof. 0.15- 500 35,000 Low Present ' interference, high method pyridinium chloride orm 0.35M

+ Tx-100 HO sensitiv_ity_ Thiocyanate Aqueous 1.0-2.5 485 29,500 Critical standing Hyashi et

amincs+Tx-100 time a!., 1986 Vanilline Ethanol 5.0-6.0 550 5,360 I Low sensitivity Goelet

semicarbazone .. al., 1988 -Vanilline Ethanol 5.8-7.0 590 5,060

I Low seasitivity I Goel et

thiosemicarbazone a!., 1988 V anillinioxime Chlorof 5.0-7.0 550 4,100 ! Low sensitivity Goel et

orm j al., 1988

'·

",, 6. APPLICATION ,,: '

Present method has been successfully employed for the determination of iron in

different samples with good results.

ENVIRONMENTAL ANALYSIS

A. Speciation of Iron in groundwater used for the human consumption . ) ( . :

The method has bee~ extensively used for determining the total iron content and its . -

speciation in the groundwater used for drinking purposes in the district of

Rajnandgaon (MP). This district lies between 20°-70' to 22°-29' north latitudes and

88° -23' to 81° -29' east longitudes in the state of MP. This district is among the least

developed districts of MP and contains 8 moderately developed towns and about

2400 villages. A large number of scheduled tribes (29%) and scheduled castes (10%)

people live in this clistrict. According to the Public Health Engineering Department

(PHED) of Rajnandgaon, nearly 95% of the rural and 55% of urban population

depend entirely on the groundwater sources for meeting its domestic water

requirement. The mode of withdrawal of the groundwater is dug-well or tube-well

fitted with hand-pumps or power-pumps. Due to the geological reasons and the over

exploitition of the gr~und water sources, the quality of the groundwater is not good

and a continuing trend of the further deterioration has been observed. The candidate - . .

has carried out an extensive analysis of the groundwater quality in the district on the - '

request of the PHED. 1be continuous monitoring and evaluation of the groumhvater

2]7

Ana/ytJcJ! studies on the Atmospheric fkpos/tJons

is undergoing. As this does not fall under the purview of this thesis, only a brief data

on the water quality of the problem villages (villages where the water quality is not

good) is presented (fable 19).·In the evaluation of the iron in the groundwater, the

present method has been applied successfully as a field method.

Summary of the chemical analyses of ground water

1000

100 i•- ' ' '" .. ~liDJ 1 };: ! ;~ }; :~ t, r : < ',·

' ~ • • ~

" ll • 1; <!

" : • • • • • ~ • :: Q ~ • " " ... :! {i ~ • ~ •

• • .. • ::: ... - ~ ;;; • :;; • ~ u "

;;:

mNum ber of sam pies analysed

•Num ber of sam pies exceeding perm Iss lble lim Its

0 Number of sam pies exce edlng excess lve lim Its

• • • • • ~ • • .. • • :!!

Fig. 7. Summary of the chemical analyses of the groundwater in · the Rajnandgaon district

Table 19. Groundwater quality observed in some problem villages of the Rajnandgaon district (mgn)

Property Prescribed standards Number Number of Number of

Permissible Excessive of samples samples samples exceeding exceeding analysed permissible excessive

limits limits Taste Un- Un- 350 37 250

Odour objectionable objectionable

pH 7.1-8.5 6.5-9.2 250 190 12

IDS 500 1500 250 65 3

Total 200 600 250 90 30 Hardness

Chlorides zoo 400 245 3 1

Sulphates 200 400 210 2 1

f·luorides 1.0 1.5 175 25 5

Nitrates 45 45 58 3 I

Iron 0.1 1.0 250 170 70

:\!anganese 0.05 0.5 50 17 ~

Analytical studies on the Atmosph~rlc Depositions

Study on the probable reason of the high iron content of the groundwater of ·

Rajnandgaon

To understand the reasons of the high iron content of the groundwater it is required

to consider the iron chemistry in natural waters. Ferrous iron [Fe(II)] in groundwater

may come from many rock forming minerals e.g.

l'yrite, marcasite

FeCO, Siderite

Vivanite

Faylite

Pyroxenes· Augite

Ferric iron occurs in variety of alumino-silicates and in three abundant oxides and

oxy-hydroxides (Bodek et al., 1988):

Fe,O, Hematite

a-FeOOH · Geothite

Y -FeOOH Lepidocrocite

Fe(OH), Amorphous ferric hydroxide

Apart from the above, iron could be present in two oxidation states of minerals like

magnetite (FeO.Fe20,) or some mica. Presence of iron in the groundwater could be a

result of the hydration, dissolution of metal hydroxide and fmally establishment of

eguilibrium in the solution. This could follow the following reactions:

M.Ob + b H20 = aM (OH) Zbta

Considering Fe20 3 a common oxide present in the crust, the aboYe equation \\ill

become:

Analytical studies on th~ Atmospheric ~posltlons

Fe20, + 3 H,O = 2Fe(OH),

Fe(OH), +3H+ = Fe'++ 3H20

Fe(OH), + 2H+ = Fe(OH)+' +2H20

Fe(OH), + H+ = Fe(OH)/ + H,O

Fe(OH), + OR = Fe(OH)4-

The above equations make it clear that the dissolution and the speciation of iron in

the water are dependent on the presen~e of the hydrogen or hydroxyl ion. Thus, the

pH of the water can be expected to play a very important role in the speciation.

Stumm et al. (1981) have shown that the concentration of dissolved metal as a

function of the pH is high in acidic medium, goes through a minimum in slightly

acidic to slightly alkaline medium and increases again in the acidic medium. In acidic

medium positively charged ferric iron Fe3+ is the dominant species and in alkaline

medium the negatively charged Fe(OH) 4- is the dominant species.

The water samples collected from Rajnandgaon were slightly alkaline to alkaline in

nature. At such pH the most abundant species to consider will be as follows:

Fe(II): Fe'+, FeOH+, Fe(OH)2°

Fe(III): Fe'+, FeOH+, Fe(OH)/, Fe(OH)4-

However, on contact with the atmospheric oxygen the Fe(II) tends to oxidise,

resulting ultimately in the formation of colloidal Fe20 3 in the water.

Method of the speciation of iron in the groundwater

DETERMINATION OF THE PARTICULATE (INSOLUBLE) IRON

Freshly pumped water was filtered through Whatman filter paper-42 (pore size 0.45

Jlm). The filter paper was digested with aqua regia and then heated to dryness. The

residue was dissolved in 0.1-M HCl and diluted to 25-ml. Rest was done as in the

determination procedure.

DETERMINATION OF IRON(III)

Thirty ml of filtered water sample was taken in a 125-ml separatory funnel and the

estimation of tot:Jl iron was done using the HCl, thiocyanate, and surfactants mix of

Am/ytlc.rl stvdles on th~ Atmospheric Depositions

CPC & Tx-100 as gtven 1n the procedure without the addition of potassium

dichromate. Thus, no oxidant was used for converting the Fe(!!) to Fe(III) oxidation

state.

DETERMINATION OF TOTAL IRON,

Total iron was determined in the similar procedure along with the addition of 1 ml of

potassium dichromate for the oxidation of Fe(II) to Fe(III) state. Difference in the

two values gave the concentration of Fe(II). The efficacy of the method was

determined by carrying out the AAS determination as described in the procedure,

with one modification that the filtered sample was treated with 5-ml of 0.1% (w/v)

ascorbic acid before the aspiration to find out the total soluble iron. Insoluble iron

was determined in the dissolved particulate phase. Result of one such determination

along with the other associated parameters that were observed (Table 20 A) and its

speciation (Table 20 B) in one problem village is shown.

Table 20 A. Physico-chemical characteristics of the ground -- --:- - f.-om Gourmati, Khairagarh Division Distt. Rajnandgaon

PH - "tofii:IUCfiV1ti

mmhos- • ::•~?-ATC

Allciliniij; ~-·; Hardness 615 730 675 800 575

-- - ca!Ciurii'-"' c ~'7231 : r -, ::--c~~31f:'~"''171'Q'i?f~I~: 2z~Y~W'il~T:':~13~~\'. Magnesium 8 · 66.6 36.6 555 57

SO<Iillffi -­Potassium

9F- ~_?ZJ !i';;~~E- _·"- --:97'"~:-: --- ·,''93 = ,: - :·)7 : 6 3 2 4 5 4

-- Manganese -

Chloride Fluoride Sulphate Nitrate

17.7 ND 326 ND

28.3 ND-212 ND

17.7 85 -Nb ---~:~_No~: ll8 21l

--ND ND-!'-:D = not d<'t<'Ct("d by standard spectroscopic methods

81.5 'ND --141 ND

32 ND 303 ND

241

Analytical studies on th~ Atmosph~rlc lkposltlons

Table 20 B. Speciation of iron in the ground water from Gourmati, Khairagarh Division Distt. Rajnandgaon (MP) P.H 62

Source Iron found by the present method Iron found by AAS

Soluble Iron . Insolu Total Soluble Insolu Total

Total· ble Iron Iron ble Iron

Fe(III) ·. Fe{Il) soluble Iron Iron - -'"-' -" '-""-

Iron .,

GovtHP 1 80 20 100 30 130 110 20 130

GovtHP 3 265 115 380 127 507 386 135 521

Private HP 1 .

---------- --

Private HP 2 253 81 335 110 444 340 120 460

Private HP 3 · ~~· 658

--- -~ ~--~------

Th1s shows that the most abundant species in the freshly pumped out groundwater at

this part of Rajnandgaon district is soluble ferric hydroxide complex of iron Fe(III),

the reasons of which have been adequately explained above.

B. Determination of iron in the rain water.

The method was employed for the determination and the speciation of iron in the

rainwater of Bhilai city l\fP. According to the procedure mentioned as above. The

results obtained are depicted (Table 21). It is interesting to note that many samples

have shO\vn the presence of the iron in Fe(II), i.e., the reduced state. Such a presence

is considered environmentally significant as it indicates the prevalence of the reducing

conditions in the cm;ronment. This aspect requires further study to find out more

au then tic conclusion.

242

Ana/ytlal studies on th~ Atmosph~rlc ~posJtlons

Table 21. Application of the method for the iron determination in rain water

PERIOD PH Pe(ll) Fe (Ill) Total Pe Total Fe found by AAS

f!moles/L f!moles/L f!moles/L f!moles/L

17/02/95 6.6 0.20 1.24 1.44 1.49

7/3/95 6.25 0.35 1.30 1.65 1.66

11/3/95 5.87 0.32 1.20 1.52 1.51

16/03/95 6.11 0.21 0.65 0.86 0.89

26/03/95 6.14 0.30 1.24 1.54 1.56

27/03/95 7.01 0.20 0.77 0.97 1.00

3/4/95 6.09 8.00 0.67 8.67 8.70

10/4/95 6.19 0.37 1.60 1.97 2.10

30/04/95 6.52 0.30 1.50 1.80 1.95

5/5/95 6.32 0.34 1.20 1.54 1.56

11/5/95 7.31 0.20 1.30 1.50 1.52 - _, ,, ··.

12/5/95 7.15 0.30 1.20 1.50 1.58

14/05/95 6.16 0.40 1.00 1.40 1.43

15/05/95 5.5 0.51 0.70 1.21 1.25

19/06/95 5.43 0.40 0.60 1.00 1.42 ·'

22/06/95 6.2 0.00 1.00 1.00 1.10

1/7/95 7.05 0.00 0.45 0.45 0.49

5/7/95 6.46 0.24 0.90 1.14 1.14

8/7/95 5.4 0.20 1.27 1.47 1.48

9/7/95 5.6 0.40 0.63 1.03 1.04

11/7/95 7.55 0.45 0.60 1.05 1.08

18/07/95 5.7 0.87 1.10 1.97 1.99

19/07/95 5.9 1.00 0.85 1.85 1.89

II. INDUSTRIALAPPLICATION:

Determination of the iron in boiler feed water.

~lethod has been successfully employed for the determination of iron in the boiler

feed water according to the procedure described above. Few results of these tests are • I '

presented (fable 22).

A/13/ytkl/ studies on th~ Atmosph~ ~positions

Table 22. Iron Determination in Boiler-Feed Water

Sample Estimated by present method, ppb AAS Determination, ppb

Treated boiler feed water 5.60 5.30

A

Treated boiler feed water 8.0 7.50

B

Raw water 2101.45 2101.0

7. CONCLUSION

This method is another useful application of the surfactants for increasing the

analytical capability of the spectrophotometric determination. In the method,

iron(III) complexes with thiocyanate ions in the presence of a cationic surfactant (e.g.

CPC) and an anionic surfactant (Tx-100). Iron is quantitatively pre-concentrated at

the least 10-15 fold by the proposed method. The detection limit at 6-fold pre­

concentration is 4-ppb iron.

Seven metals: iron(III), cobalt, uranium(VI), niobium(V), molybdenum(V),

tungsten(V) and rhenium form complexes with the thiocyanate coloured enough to

be determined spectrophotometrically. For iron determination the thiocyanate

method is attractive as the determinations can be carried out even in the strongly

acidic solution with good sensitivity. This chapter reports here· the ~se of the

surfactant mixtures for the extraction of iron and the chemistry in:Volved in these

extraction methods is elucidated.

Various water immiscible organic solvents were tested for their efficacy of extraction

of the complex. Acidity of the solution does not affect much the colour strength of

the Fe(III)-thiocyanate complex.

A rebtive excess of the thiocyanate ions is desirable in the iron-thiocyanate reactions.

\\'orking concentration adopted was 0.25-i\1 thiocyanate. The sensiti\ity of the

reaction between the iron(III) and thiocyanate is largely dependent on the numbcr of

the thiocyanate ions co-ordinated "ith iron(III). The reaction mechanism and

composition of the iron(III)-thiocyanate complex in the presence of the surfactant

mixture is elucidated. This composition is compared with other reported complexes

to describe the chemistry of the iron complexation.

Iron(III) can form a variety of complexes depending on the number of the

thiocyanate ions co-ordinated with the Fe(III). At low thiocyanate ion concentrations

iron(III) forms [Fe (SCN)] 2+ predominantly. At 0.1 M concentration of thiocyanate

the resulting complex is mainly [Fe (CNS),f. In the present investigation, the

thiocyanate concentration was 0.27 M, which should favour the formation of

negatively charged iron(III)-thiocyanate complex, stabilised by the cationic surfactant.

The anionic surfactant or amides help in the quantitative extraction of the complex

leading to higher extraction efficiency and the molar absorptivity. This reaction

mechanism is theoretically sound, is supported by the practical evidences, and thus

beautifully explains the chemistry of the iron(III) determinations by thiocyanate

method involving the surfactants or other organic reagents.

Ions commonly associated with iron in the natural waters were tolerable in the

method under the optimised conditions established. Presence of the reducing agents

viz. tin chloride, ascorbic acid oxalic acid etc. obviously interfered with the iron

determination by converting the Fe(III) into the Fe(II).

Some reported methods for the iron determination have been compared. The

present method is simple, sensitive and adaptable for the field use. The method has

been successfully employed for the determination of iron in different samples with

good results for the speciation of the iron in the groundwater used for human

consumption. The method is also used for the determination of iron in rainwater and

its speciation. The determination of total iron in the boiler feed water is also carried

out with satisfactory results. Method could be applied directly to the determination of

iron in environmental samples and boiler feed water where very low concentrations

are required to be determined. There is a scope to study the effects of other reagents

in conjunction with the thiocyanate. However, the chemistry of thos~ reactions may

be similar to the one established here.

AMiytk•l stud/ .. on lh• Atmosphorlc O.pos/t/ons

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LIST OF PAPERS PUBLISHED/COMMUNICATED BY THE

CANDIDATE

1. "POLY AROMATIC HYDROCARBONS IN PROGRAM TEPUCE AREA". Published in

"Toxicology and Environmental Chemistry", the Netherlands, 1997, Volume 58,

Page 25. Copy enclosed.

2. "TRACE ELEMENTAL COMPOSITION OF ATMOSPHERIC PARTICULATE AT BH!LAI

IN CENTRAL-EAST INDIA". Accepted for publication in "TI1e Science of the Total

Environment", the United Kingdom, Volume and Page number awaited. Copy of the

first page of the galley proof enclosed.

3. "POLYCYCliC AROMATIC HYDROCARBONS: NEED FOR ASSESSMENT OF

HEALTH RISKS IN INDIA? STUDY OF AN URBAN INDUSTRIAL LOCATION".

Accepted for publication in "Environment Monitoring and Assessment'' The

Netherlands, MS number- EMAS 500. Letter of acceptance pending modifications,

enclosed.

_( .. )

4. "CONCENTRATION OF MERCURY AND OTHER HEAVY METALS IN CENTRAL

INDIA". Accepted for publication in the book "Mercury Contaminated Sites:

Characterization, Risk Assessment and Remediation" Ebingha;_k· R., Turner, R.

R., Lacerda, D., Vasiliev, 0., Salomons, W. (Eds.), Springer Environmental Science,

Springer Verlag Heidelberg, in press. Letter of acceptance enclosed.

5. "A SENSITIVE METHOD FOR QUICK DETEIThUNATION OF. IRON IN

ENVIRONMENTAL AND INDUSTRIAL SAMPLES". Communicated to the ":-.likro

Chemica c\cta" :\ustriJ, .\IS no. 97270.

6. "CHEMISTRY OF ATliiOSPHERIC PREOPITATION AT TWIN OTY OF BHILAI-0URG

IN CEr-..'TRAL-EAST INDIA". Communicated to the ".\tmospheric Fm·irnnmmt", the

Lntted f..:ingdnm.

OTHER PUBLICATIONS/PRESENTATIONS

1. "Pre-concentration and Determination of Certain Metal Content in Suspended

Particulates". Accepted for presentation in the 1997 Pittsburgh Conference, AtlJnta,

USA. Letter of acceptJncc enclosed.

2. ''Polycyclic Aromatic Hydrocarbons: Need for Assessment of Health Risks in

India? Study of an Urban Industrial Location." Accepted for oral presentation in

the 'International Conference on Industrial Pollution Jnd Control Technologies',

Hyderabad, 1997

3. "Field Detection and Determination of Iron in Atmospheric Particulate

Matter." Published in Proceedings of the Thirty-third Annual Convention of

Chemists, Coimbatore, 1996, ANAL(PP)-4.7, Page D-7.

4. "Polycyclic Aromatic Hydrocarbons in Czech Environment." Published in EPA

Peer Review Proceedings, Trest, tl1e Czech Republic.

:J. "Atmospheric Concentrations of Trace Elements in Urban Air of Central

India". Accepted for presentation in the "World Congress on Air Pollution m

Developing Countries" Costa Rica, South America.

6. "Polycyclic Aromatic Hydrocarbons in Central Indian Urban Air". Accepted

for presentation in the "World Congress on Air Pollution in Developing Countries"

Costa Rica, South America.

7. "Vegetation-Atmosphere Distribution of the PAH's" Presented in the National

Seminar on Persistent Organics in Food -Chain at Milovy, the Czech Republic (Sept

19-21 1994.)

8. "PAH's in Northern Bohemia Region"

Presented in tl1e National Seminar on Persistent Organics in l'ood -Chain at :\!ilo,-y,

tl1e Czech Republtc (Sept 19-21 1994.)

9. "Acidification of the Environment: An Analytical Review" Presented Jnd

publtshcd in the Proceedings of :\atioml Seminar on Ecology and Em·ironmcnt

Rl11b!, India, 1993.

I 0. "Sulphate Resistance of Cements" prcsm ted in the Slminar on the s:unc topiC

nrg:u1iscd by the lmtitutlnn of F.ngu1l-crs Bhibi, lndta, 19').).

ELSEVIER The Science of I he To! a I Emuonmcnl 00 (1998) 00-00

the Science of the Total Environment .. , .. ___ ... __ _

............ --... - ... -

Trace elemental composition of atmospheric particulate at Bhilai in central-east India

Ab!.tract

P .K. Pandey'·*, K.S. Patel b, P. Subrt'

• Dt•parrment of Ensmt•enng Cht!ml511)', Bflilm /nsl/lute of TecJuwfo~·· Bhi/ai House Dwg. Blulai, 491002 MP, India ~S. 0. S. in Chem/S/t)', Pt. R. S. SlwJJa University, Raipur, MP, f11dia

cAnal)IICal Lab, Regional H_1giwe Station, Us11 n. L, TI1e C:ech Republic

Received 17 September 1997; accepted 3 J;muary 1998

The atmospheric concentration of the particulate trace elements and compounds: chloride~ nitrate, sulphate, fluonde, arsenic, beryllium, cadmium, copper, iron, manganese, nickel, lead, titanium, vanadium, and zinc were determined at two sampling stations located at Bhilai, an urban industrial location. It is the first such study in this part of India. Sampling sites were free from near source effect; 24·h samples were collected once every week by a high volume sampler on a glass fibre filter. Particulates collected from May 1995 until April 1996 were extracted employing an automatic digestion system. An inductively coupled plasma spectrometer equipped with an ultrasonic nebuliser (ICP·OES·UN) was used for elemental analysis. Anions were determined by ion·chromatography. High concentrations have been obtained for many elements. Enrichment calculations show high enrichment of Zn, Pb, Cu, Cd, As, Be and Cl. Seasonal variation has been noticed and during the rainy season there was a significant lowering in the pollutant \evets. Statistical analysis has been carried out to deduce the effect of meteorological and source effects. Close correlation between benzo[a]pyrene (BaP), benzo[glii]perylene (BghiP), lead and vanadium levels shows the contribution of vehicular and industrial emissions and on the basis of a lower BaP /BghiP ratio the vehicular emission appears to be the major contributor of certain elements in the particulate. The levels of many elements are higher than the results obtained in various other parts of the world. © 1998 Elsevier Science B.V.

Keywords: Aerosol; Atmospheric pollution; Trace elements; ICP·spectroscopy; India

• Corresponding author. Fax: + 91 788 323997.

0048-9697j98/S19.00 © 1998 Elsevier Science B. V. AU rights re~rved. PI/ 50048·9697(98) 00111·9

Tt!XIco/ogicu/ und F.nvimnmtntal Chtml:stry, Vol. 58, pp. 25-32 Reprint\ ~vadJhlc directly from the publl~her l'hotocopywg permuted by license only

0 1997 OPA (Overseas Puhli~hers A~qociation) Am,tcrdam R.V. Puhli\hcd in 111e Ncthcrluntb

under ]icen~ by Gordon ond Breach Science Publi~hcrs Printed in Malaysia

POLYCYCLIC AROMATIC HYDROCARBONS AT 'PROGRAM TEPLICE' SITES IN THE

·CZECH REPUBLIC

JAN LENICEK'··, MILAN SEKYRA1, PIYUSH PANDEY', MARIE

CITKOVA.', IVAN BENES', JITKA NOVOTNA', SIGRID KOCIA.NOV A', JEVGENUA HELASKOV A' and ANNA SIMONOV A'

1 Refional Hygiene Station, Moskevskd I 5, 400 78 Ust( n.L., Czech Republic Bhilai Institute of Technology, Bhilai House Durg 49/00IMP, India

1 Regional Hygiene Station, Wolkerova 4, 4I665 Teplice, Czech Republic

(Received I6 May I996)

Determination of polynuclear aromatic hydrocarbons in air was carried out in two monitoring sites of 'Program Teplice' throughout the year 1993. The town of Teplice is located in an industrialized reg10n of the Northern Bohemia, Prachatice, a small town in Southern Bohemia, was chosen as reference. Measurement for PAHs was done in air at both locations and in bulk deposition at Teplice. Analysis of PAHs was done in air by HPLC with fluorescence monitor and in bulk deposition by CGC-MS. Difference in the mean PAHs levels in air is not significant; particularly when taking benzo(a)pyrene as an indicator compound. Higher concentrations of PAHs were observed during the winter heating period at both locations.

Keywords: PAH~ HPLC; benzo-(a]-pyrene

INTRODUCTION

Czech environment is still passing through a period of crisis on the account of the adverse effects arising from an extensive industrialization under a centrally planned economic system. Safe environmental and industrial practices have not received adequate attention. The result is a deterioration of environmental quality, ·extensive loss of forests and lowering of the standards of human health. The north-west part of Czech Republic, which

• Corresponding Author.

25

26 1. LEN(CEK et al.

comprises four districts, and are collectively referred to as Northern Bohemia, is probably the most affected area of Europe'''· Extensive strip-mining of brown coal and numerous coal based industries [power plants, 'heavy engineering and chemical plants, wood processing and paper mills] is the main feature of this region.

The problem of pollution in this region which borders the coal mining districts of two other countries-Germany and Poland, is so serious that even in scientific community it is called- 'The Black-Triangle'.

Previously, circumstanses prevented collection and dissemination of scientifically valid data on environmental quality; thus, there exists only fragmented and often sketchy information on the real extent of pollution.

A long term program on monitoring and research entitled on "Impact of Environmental Pollution on the Health of Population at the District of Teplice, Czech Republic" was conceived in 1991 by the Czech Ministry of Environment. In 1992 it was incorporated in the PHARE program and has also been supported by the Environmental Protection Agency [EPA], USA, Norwegian Institute of Air Research [NILU] and it is now referred to as 'Program Teplice'. The name Program Teplice derives from the town of Teplice which is situated in the north-west region of the Czech Republic [formerly, Northern Bohemia) and both its environmental and rneterological 'conditions are representative of the whole region. Prachatice, situated in the south-west [formerly, Southern Bohemia) was chosen as ref~rence site for the comparison of environmental conditions. It is one of the cleanest parts of the Czech Republic and most of the district is "Protected Landscape Area". About 52% of the area is under thick spruce forest cover.

Data for the levels of PAHs in Czech environment is fragmented or almost non-existent'''· To our knowledge, this study under the Program Teplice is the first comprehensive study in Czech Republic on monitoring and evaluntion of the various aspects of the PAHs in the selected sites, mentioned above. Results of this study will help towards creating a real data base on U1e levels of PAHs in European atmosphere; particularly that of Central Europe.

MATERIALS AND METHODS

Sampling and Extraction

Air Samples

The sampling site in Teplice was located in the centre of the town not subjected to a near source or intense vehicular traffic. The sampling site in

POLYCYCLIC AROMATIC HYDROCARBONS 27

Prachatice was located in District Hygiene Institute and this too was not affected by any near source. Samples were collected from January to December 1993. During heating period (January, February, November, December) the samples were collected every day and from April to August every third day in Teplice and every sixth day in Prachatice. At both sites ambient air samples about 20 m' were collected using Versatile Air Pollution Sampler (VAPS; University Research Glassware, N.C.) during 24 hours periods. VAPS is a modified dichotomous sampler that collects two fine particle samples (< 2,5 !J.m) and a coarse particle sample (2,5 to 10 IJ.m) simultaneousJyr". Fine particles were collected on the teflon and coarse particles on nucleopore filters. Filters were kept in Petri dishes at 22°C and 30% relative humidity for 24 hours and weighed on Mettler MP-5 balances. Particulate PAHs were(< 2,51J.m) collected on quartz filter and polyurethane foam plug was used downstream for the adsorption of PAHs in vapour phase. The quartz filter was extracted with 20 mL of 10% methanol in dichloromethane on ultrasonic extractor (300 W) for 20 min. The polyurethane foam (PUF) was extracted in Soxhlet extractor with a mixture of 10% ether in hexane for 6 hours (10 cycles/hour). The combined extract was evaporated in a rotary vacuum evaporator to about I 0 mL and 3 mL of cyclohexane was added. It was then evaporated to about 2 mL volume.

The extract was fractionated by Silica gel column chromatography. Ten mL of initial hexane eluent was discarded and next fraction of 30 mL eluted with 6% acetone in hexane was collected; evaporated to a small volume-first, in a rotary vacuum evaporator, then to dryness in a stream of ultra pure nitrogen. Redissolution was done in 2-10 mL of methanol for HPLC detennination.

Bulk Deposition

Samples were collected in a stainless steel vessel (0.7 m x 0.7 m) during 24 hours sampling period at Teplice. This sample collector was not equipped with a separate sensor device for the collection of rain or snow respectively; therefore, it provided the measurements for total water soluble part of deposition. Sample (I liter) was passed through a teflon filter (pore diameter 5.0 mm). The filtrate was then passed through a cartridge filled with 0.5 g of C 18 silica. This cartridge was conditioned previously with 5 mL of hexane, 5 mL of methanol and 5 mL of water.

The cartridge, after passing the filtrate, was dried in vacuum for 20 min. It was then eluted with 2 mL of hexane. The hexane extract was evaporated to dryness under a stream of nitrcgen and was re-dissolved in 0.5 mL of toluene.

28 J. LEN(CEK et al.

Instrumental Procedure

Instrumental procedure adopted was largely based on EPA method T0-13.141

In brief, Hewlett Packard [HP 5890 II] gas chromatograph with mass detector [HP 5971] was used for the analysis of bulk deposition. Analysis of air was done with Spectra Physics [SP8700] HPLC with fluorescence monitor Kratos FS-970.

GC-MS was equipped with a HP-5 column of 25 m x 0.2 mm x 0.33 )lm dimension, injection mode was splitless at 230°C, initial oven temperature was 70°C for 2 minutes, ramped at l0°C per minute to a final temperature of 300°C and held for 13 minutes. Detection was done by electron impact (70 eV) in SIM mode.

HPLC was fitted with Tessek ODS [5 J.lm, 250 x 4 mm] column and Tcssek ODS [7 J.lm, 30 x 4 mm] precolumn. Gradient flow was 0.7 ml per minute beginning with 80% methanol and 20% water from 0-20 minute and 100% methanol from 20-30 minute. Detection was made at a fixed excitation of 280 nm and emission of 370 nm.''l.

Recoveries were determined by spiking and the average recovery was more than 90%. Quality of the analytical procedure was determined by analysis of NIST standard reference material SRM 1649-urban dust sample and multiple injections of the standards; frequently during the course of analysis.

RESULTS AND DISCUSSION

Eight PAHs in air and sixteen in bulk deposition were monitored throughout the year 1993. There were carried out 388 analyses- 188 air samples from Teplice, 119 from Prachatice and 81 bulk deposition samples from Teplice.

Table I and II, presents mean concentration of PAHs in air and bulk deposition.

TABLE I PAJ Is in air 1993

Compound Teplice Pracflatice Mean[nglm'} S.D. Meanfnglm1] S.D.

Phenanthrene 45 51 30 27 Fluoranthene 29 38 20 22 Pyrene 28 4! 16 19 Benzo(a)anthracene 8.4 12 6.2 9.1 Benzo(k)fluoranthene 4.7 6.6 4.0 5.4 Benzo(a)pyrene 4.8 6.9 3.5 5.1 1ndeno( 1 ,2,3cd)pyrene 6.0 7.9 4.5 6.9 Bcnzo(ghi)pcrylene 3.8 5.4 2.6 3.4

POLYCYCLIC AROMATIC HYDROCARBONS 29

TABLE II PAHs in bulk deposition, TEPLICE 1993

Compound Mean[ng!L] S.D. Range[ngfL]

Naphthalene 172 299 2360 Acenaphthalcne 64 99 570 Acenaphthcne IS IS 104 Fluorene 82 117 866 Phenanthrene 276 369 2771 Anthracene 44 39 233 Fluoranthene 131 115 536 Pyrene 78 71 312 Benzo(a)anthracene 11 13 65 Chrysene 23 22 110 Benzo(b )Jluoranthene 16 17 79 Bcnzo(k)fluoranthene 18 17 78 Benz.o(a)pyrene 8.1 . 13 64 Indcno(l ,2,3cd)pyrcnc 18 23 103 Dibenz(a,h)anthracene N.D. N.D. N.D. Benzo(ghi)perylene 14 13 63

N.D."" Not detected.

Mean sum of all PAHs quantified during the study year was 970.1 ng/L in bulk deposition at Teplice; 129.7 ng/m' in air at Tcplicc and 86.8 ng/m3

at Prachatice. Most predominant compound was phenanthrene in air and naphthalene and phenanthrene in bulk deposition.

Mean concentration of the index species; benzo(a)pyrene was 8.14 ng!L in bulk deposition and 4.78 ng/m3 in air, both at Teplice and 3.49 ng/m3 in air at Prachatice. Its range in bulk deposition was 64.0 ng/L and 41.0 ng/m'; 32.4 ng/m' in air at Teplice and Prachatice respectively. This points to episodes of high concentration in the environment and in view of proven mutagenicity and carcinogenicity puts the population at risk. Correlation between benzo(a)pyrene and fluoranthene is very high [R,,=0.93] Figure l. and fits the linear equation:

CA, = k· CsraJP + q; where k and q are constants

Similar correlation in higher orders is obtained for other PAHs are giveri in Table III which indicates a constancy in the relative concentration of various PAHs in both sampling locations during the course of the study. Constants k and q are quite similar in both places which again suggests a similarity in the sources of emission, too. Results obtained are in a good agreement with those found during a short tenn study conducted by the labl'r.

We tried to establish a correlation in the B(a)P concentration and PM 2.5 [particulate matter of 2.5 mg or lesslm'] values in air at both locations. Correlation values are 0.51 for Tcplice and 0.29 for Prachatice but the

30 J. LEN(CEK eta/.

TABLE liJ PAHs in air, correlation with benzo(a)pyrene

Teplice

R ~·-

~:::::: 6.63 X g(Baw>(a)pymlo:) + 13.28 0.823

5.30 X + 3.63 0.930 c(l'yrl:ne) = 5.60 X

dll<nz.o(a)pyralo) + 1.16 0.898

(ll<nz.o(o)p)>rme)

c(B•nn>~•)an~) 1.70 X ~(Benw(alpyJmt) + 0.23 0.973

C\Brnzo(klnutn~~m.ne) = 0.90 X + 0.39 0.892 (Bmzo(l)pyrme)

~tBenUilgh,)pefylene) = 0.73 X C (lknltl(a)pym>e) + 0.27 0.871

Unden<~l.2,lc.dl~renc) 1.07 X c(ll<nz.o(a)pym>e) + 0.93 0.873

Prachatice

Rl<jU&n:

c,,~o ..... u,.,.> 4.79 X c(lklv.o!o)p)'Tal<) + 13.28 0.808 c(Pl.,..,,....,..} 4.10 X c(ll<nz.o(alpym>c) + 4.65 0.928 c(Pyre<>e) 3.66 X c(~o)pyru><) + 3.29 0.923 c(B<Dl.O(a)alltltn=e) 1.77 X c(Baw>(o)pyreoc) + 0.06 0.964

~:::::;::' 1.04 X ctBcnrD(•lpy=<l + 0.35 0.940 0.65 X c(Bcnzo(•)py<mt> + 0.33 0.940

(Jndetlall,l,'kdll')"rene) 1.26 X c(Bcnwl'o)pyrene) + 0.11 0.855

difference in the yearly mean of PM2.5 is very high -80.4 Teplice and 11.5 Prachatice. The corresponding trend has been observed for the PM I 0 values 98.2 Teplice and 44.2 Prachatice (Fig. 2). These values signify the impact of industrial activities at Teplice and it could be a matter of further studies concerning human health. ·'

Quarterly distribution pattern of B(a)P in both air and bulk deposition have shown higher concentrations during the 4th and 1st quarter that is during

2l0

200

50

0

./ / .

-/. ·'7{-. . . !Uq-(),93 , ...

0 10 20 30 40 ll(•)P ng:mJ

FIGURE l Correlation between B(a)P and fluoranthene-air Teplice (n=l88).

PM%,3 PM tO 140,----------------,~---,

"" t--f:l-------m---1 100 t---li.l------..--\11---1

'E 80 h::r-ft---------lfl--"li'J----i ~~~r------f,~r---1

: ti{t_:t,J;-_::-_--_--_ -1--t' I F ·~~~~-+~~~~~

M~S.D. MamS.D.

t:JTc-plM IIPTllehali&:G

FlGURE 2 Comparison of fine and come particles in monitored sites.

POLYCYCLIC AROMATIC HYDROCARBONS 31

Air Teplice Air Prachatlte

.----.~ rffi1~1l~. '" lo,sii~ "" ""' ..

I o,12 ""

FIGURE 3 Comparison of quarterly distribution and mean concentration of B(a)P in the environment.

winter period from October to March and more than 90% of the total concentration of B(a)P and thus all PAHs are recorded in this period Figure 3.

This clearly points to the higher energy consumption for heating purposes which subsequently leads to higher consumption of organic fuels both in houses and industries. The highest concentration of B(a)P in air at both sampling sites was found during the first quarter of the year whereas in bulk deposition in was more or less constant in both and first and last quarter of the year.

As far as source allocation is concerned; the use of lignite for domestic heating and many industrial processes is, apparently, the major cause of emission of these organic pollutants. However, contribution and differences in the emission profiles from the vehicular traffic [mainly in Teplice) and wood combustion [predominant in Prachatice) could not be ruled out.l6l

Presence of PARs in air and rain water can lead to their accumulation in the food chain and the subsequent human exposure from ingestion''· 81 •

CONCLUSIONS

Levels of PARs in air were monitored at two 'Program Teplice' sites throughout the year 1993. PARs in the bulk deposition was monitored at one site.

32 J. LENfCEK <t a/.

Levels of PAlls, percentage distribution of carcinogenic PAlls and the distribution profile is very similar in air at two sampling locations of Program Teplice area. It is feasible that this might be done due to similarity of predominant sources. During winter when the fuel consumption for home heating and power generation is high; a higher concentration of PAlls is observed. Bulk deposition was found to be very high in the PAlls levels during winter period.

Acknowledgements

This work has been supported and granted by the Ministry of Environment C.R.; Environmental Protection Agency of United States and CEC of PIIARE

:Program II EC-HEA-18 C2. This paper has been Peer reviewed and approved for publication. However, the agencies mentioned above do not necessarily agree with views expressed. The mention of any t~ade name constitute any app-roval for purchase. One of the author PP acknowledges the support of the Ministry of Education C.R. and Hygiene Services C.R.

- References

(I] Proceedings of Peer Review Workshop - Program Teplice. Introduction, 1992, p. 3. ,. [21 Nondek, L. (1991 ). Nature, 354, 180

[3] Stevens, R. K., Pinto, I. P., Mamane, Y., Ondov, J., Abdulrahccm, M., Al-Majcd, N., Sadek, M., Cofer, W., Ellenson, W. and Kellogg, R. (1993). Water Sci. Tee/mol., 27, 223-233.

[4] Winberry, W. T., Murphy, N. T. and Riggin, R. M. (1990). Methods for Determination of Toxic Organic in Air, EPA Methods, NoyesData Corporations, Hill Road, Park Ridge, New Jersey, p. 370-466.

[51 Lenicek, J., Sekyra, M., Cftkova, M. and Holoubek, !. (1993). Cent. Euro. J. Pub. Health, ' - 2, 113-1!6. [6] Watts, R., Lewtas, J., Stevens, R., Hartlage, T., Pinto, J., Williams, R., Hattaway, K.,

Ml;kov3, I., Benes, I., Kotcsovec, F. and Sr:im, R. (1994). Inter. J. Envimn. Anal. Chem., . 56, 271-287.

[7] Sekyra, M., Sevcfk, J., Lenicek, J., Cftkova, M. and Benes, I., Polycyclic Aromatics ~~- Hydrocarbons in Beer and Wine (in Czech), Hygiena (In press).

[8] Hattcmcr-Frey, H. A. and Travis, C. C. (1991). Toxicology and /11(/i.utrial Ilealth, 7, 141-157.

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