1

Application of Polymer Inclusion Membrane for Selective Extraction, and On-line Separation-Determination in

Flow Injection Analysis System of Vanadium(V)

Mohammad Reza Yaftian

Department of Chemistry, Faculty of Science, University of Zanjan, Zanjan, IranSchool of Chemistry, The University of Melbourne, Victoria, Australia

Sabbatical Leave Report)August 2016-July 2017(

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Polymer Inclusion Membranes (PIMs)

● Liquid membranes (BLM, ELM and SLM) were proposed as possiblealternative to conventional solvent extraction.

● Polymer-based liquid membranes have been known for over 40 years;early applications in construction of ISEs.

● Exhibit excellent stability and versatility, in comparison with otherliquid membranes such SLMs.

● More stable than SLMs; entangling of the constituents within thepolymer vs. instead of attached to a porous support by capillaryforces.

3

Other Terminologies for Polymer Inclusion Membranes

● Polymer Liquid Membranes

● Gelled Liquid Membranes

● Polymeric Plasticized Membranes

● Fixed-site Carrier Membranes

● Solvent Polymeric Membranes

4

L.D. Nghiem, P. Mornane, I.D. Potter, J.M. Perera, R.W. Cattrall, S.D. Kolev, J. Membr. Sci. 281 (2006) 7-41.

Polymer Inclusion Membranes Compositions

● Extractant (Carrier)The carrier is essentially a complexing agent or an ion-exchanger,responsible for binding with the species of interest and transporting itacross the PIM.

DEHPA Aliquat® 336

5

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Ionic Liquids Properties; Suitable Extractants

● Non-molecular solvent

● Very low vapor pressure

● High thermal stability

● Tunable viscosity

● Tunable miscibility with water and organic solvents

Phosphonium-based ionic liquids (Cyphos family) in PIM researchL. Vidal, M.-L. Riekkola, A. Canals, Anal. Chim. Acta 715 (2012) 19-41.B. Pospiech, W. Kujawski, Rev. Chem. Eng. 31 (2015) 179-191.A.R. Hajipour, F. Rafiee, Org. Prep. Proced. Int. 47 (2015) 1-60.

(CH2)13CH3P

H3C(H2C)5

H3C(H2C)5

H3C(H2C)5

Cl-

Cyphos® IL101

Polymer Inclusion Membranes Compositions (continue)

● Base Polymer- Provides the membrane with mechanical strength- CTA, PVC and PVDF-HFP are the most used

CTA PVC PVDF-HFP

7

PVDF-HFP advantages- High hydrophobicity- Good thermal property- Excellent mechanical properties- High resistance towards acids- Suitable solubility in THF

Polymer Inclusion Membranes Compositions (continue)

● Plasticizer (Modifier)- Improves the compatibility of the membrane components- Provides elasticity and flexibility of the membrane- Carrier also acts as a plasticizer

2-NPOE TBP

DOP

8

Analytical Applications of Polymer Inclusion Membranes

● Extraction ProcessesY. O’Bryan, R.W. Cattrall, Y.B. Truong, I.L. Kyratzis, S.D. Kolev, J. Membr. Sci. 510 (2016) 481-488.

● Transport StudiesD. Wang, R.W.Cattrall, J. Li, M. I. G.S. Almeida, G.W. Stevens, S.D.Kolev, J. Membr. Sci. 542 (2017) 272-279.

● Construction of Paper-based SensorsB.M. Jayawardane, L.d. Coo, R.W. Cattrall, S.D. Kolev, Anal. Chim. Acta 803 (2013) 106-112.

● Manufacturing of Passive SamplersM.I.G.S. Almeida, A.M.L. Silva, R.A. Coleman, V.J. Pettigrove, R.W. Cattrall, S.D. Kolev, Anal. Bioanal.Chem. 408(12) (2016) 3213-3222.

● Preparation of nanoparticlesY.Y.N. Bonggotgetsakul, R.W. Cattrall, S.D. Kolev, React. Funct. Polym. 97 (2015) 30-36.

● On-line Extraction-separation for Selective DeterminationsL.L. Zhang, R.W. Cattrall, M. Ashokkumar, S.D. Kolev, Talanta 97 (2012) 382-387.

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Evolution of the PIM Papers (1991-2017)

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Source: Web of Science

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Part I

Selective extraction of V(V) from sulfate solutions into a polymer inclusion membrane composed of poly(vinylidenefluoride-co-hexafluoropropylene) and Cyphos®IL 101

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Vanadium; Strategic Industrial Material

● Hardness● Fatigue resistance● Tensile strength● Good corrosion resistance● High melting point

Vanadium; Common Applications

● Catalysts for the desulfurization process in the petroleum industry

● In batteries, military equipment, fuel cells, nuclear reactors, cars, andceramic products

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Vanadium; Production

● Hydrometallurgical processes from- Vanadium-containing ores- Chromium-bearing vanadium slag- Stone coal

● Recycling from secondary sources- Scarcity/depletion of vanadium containing ore reserves, and- Increased consumption.

● Significant secondary source ofvanadiumSpent hydrodesulfurisation catalyst which also contains molybdenum,cobalt and nickel on an alumina carrier.

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Vanadium Recovery

● Solvent Extraction- Z. Zhu, K. Tulpatowicz, Y. Pranolo, C.Y. Cheng, Hydrometallurgy 154 (2015) 72-77.- P. Ning, X. Lin, X. Wang, H. Cao, Chem. Eng. J. 301 (2016) 132-138.- G. Zhang, D. Chen, W. Zhao, H. Zhao, L. Wang, D. Li, T. Qi, Sep. Purif. Technol. 165 (2016) 166-172.

● Supported Liquid Membrane- L.J. Lozano, C. Godínez, F.J. Alguacil, Hydrometallurgy 80 (2005) 196-202.- M. Hor, A. Riad, A. Benjjar, L. Lebrun, M. Hlaïbi, Desalination 255 (2010) 188-195.- S. Nosrati, N.S. Jayakumar, M.A. Hashim, S. Mukhopadhyay, J. Taiwan Inst. Chem. Eng. 44 (2013)

337-342.

● Polymer Inclusion Membranes- No Report At All!!!

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Why This Study Was Designed?

● Importance of the recovery of vanadium from spent catalystscontaining molybdenum

● Demonstration of the potential of the PIM technique for the extraction-separation of vanadium ions

● The sulfate media was selected because the leaching from rawmaterials and the secondary sources containing vanadium are widelyperformed with sulfuric acid

● Known extractive properties of the ionic liquid trihexyl-tetradecylphosphonium chloride (Cyphos® IL 101) towards V(V) andMo(VI) ions

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Membrane Preparation

PIM preparation procedure using a Teflon casting knife

PVDF-HFP Based PIMs

17

Membrane Preparation (continue)

PVC Based PIMs

Suitable membranes:- Transparent- Flexible- Resistance to mechanical stress

(tearing and stretching)

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PIMs formed by:55% PVDF-HFP35% Cyphos IL10110% NPOE

● 3.5 cm diameter● 0.068 ± 0.002 g● 104 ± 10 mm thickness*● 0.68 ± 0.04 g cm-3 density

* using a stereo microscope with 60× magnification (SMZ-140, Motic, China) in combination with a microscope camera (MotiCam 1000, Motic, China).

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Extraction/Back-extraction Procedures)

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Metal Ion Determinations

Spectrophotometric method, using xylenol orange; modified/establishedfor a FIA system for determination of V(V) in solutions containing no othermetal ions/no acidic solutionsB.V. Agarwala, A.K. Dey, Mikrochim. Acta (1969) 664-667.

Reaction coil

waste

Injection valve

Xylenol orange (0.005%) in CH3COOH/CH3COONa pH 5.1

Buffer solution CH3COOH/CH3COONa pH 5.1

Peristaltic pump-I

Peristaltic pump-II

T Detector (512 nm)

PC

LR: 0.25-5.0 mg -1

LOD: 0.13 mg L-1

RSD: 3.0% (n = 5, V concentration 3 mg L-1)

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UV-Vis spectrophotometer: Libra S12, Biochrom (UK)

Peristaltic pumps: Alitea (Sweden)/Gilson (France)

Tygon pump tubing (0.76 mm i.d., TACS, Australia)

Low-pressure injection valve Rheodyne (5020, USA)

Sample loop (50 mL), Reaction coil (0.5 m, 0.5 mm i.d. Teflon, Supleco, USA)

Data acquisition: ER280, eDAQ, Australia

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Metal Ion Determinations (continue)

Inductively Coupled Plasma (ICP-OES); determination of vanadium and other metalions in their mixtures or in highly acid media

Perkin Elmer Optima 4300DV Spectrometer

Plasma flow rate: 15 L min -1 Sample flow rate: 1.5 mL min -1

Auxiliary flow rate: 0.2 L min-1 Washing time: 30 sNebulizer flow rate: 0.8 L min-1

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Selection of Base-Polymer

Aq. Phase: PIM:V(V) (50 mg L-1) 70/30 wt% PVDF-HFP or PVC/Cyphos® IL 101Sodium sulfate (0.2 mol L-1)pH 2.1

.Likely reason; better flexibility of PVDF-HFP chains leading to less diffusive resistance to themass transfer of the V(V)-Cyphos® IL 101 adduct within the membrane.

Y. O'Bryan, R.W. Cattrall, Y.B. Truong, I.L. Kyratzis, S.D. Kolev, J. Membr. Sci. 510 (2016) 481–488.

PVDF-HFP

PVC

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pH Dependency Distribution of V(V) Speciesin Sulfate solutions

V(V) species in sulfate solutions (depends on concentration and pH):VO2

+, VO2SO4-, H2VO4

-, HVO42-, H2V10O28

4-, HV10O285-, V4O12

4-, HV2O73-, and V2O7

4-.

X. Zhou, C. Wei, M. Li, S. Qiu, X. Li, Hydrometallurgy 106 (2011) 104–112

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Effect of the Solution pH

pH:× 0.6 ▲ 1.1 ♦ 1.6 ■ 2.1 ● 2.3

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Selection of an Appropriate Plasticizer/Modifier

PIMs compositions:70 w% PVDF-HFP and 30 wt% Cyphos® IL 101 (no modifier)70% 70 w% PVDF-HFP, 25 wt% Cyphos® IL 101 and 5 wt% plasticizer/modifier.

Remember that application of plasticizer (modifier) results in:- Flexibility of the membrane- Solubility of the extracted species

27

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Optimization of the PIM Composition

Parameters to be considered for selecting a PIM:

- Appearance- Mechanical stability- Extraction efficiency- Extraction rate

Tested compositions:

- PVDF-HFP 50-75%- Cyphos® IL101 20-50%- NPOE 0-20

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Successful PIMs

PIM ID Cyphos® IL 101

(wt%)

NPOE

(wt%)

PVDF-HFP

(wt%)

Percentage extracted V(V) after 6 h

(%)

1 20 5 75 36.4 (±1.6)

2 25 5 70 43.3 (±1.8)

3 30 5 65 56.8 (±2.2)

4 35 5 60 67.5 (±2.0)

5 35 10 55 75.8 (±1.9)

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Effect of the Aqueous Solution Compositionand Mechanism of V(V) Extraction

Na3VO4 in 0.2 mol L-1 Na2SO4

Colorless (pH 10.8) -----> Yellow (pH 2.3) ----> Colorless after 2 h

VO43- + 4H+

VO2+ + 2H2O

H2VO4- + 2H+

VO2+ + 2H2O

HVO42- + 3H+

VO2+ + 2H2O

H2V10O284- + 14H+

10VO2+ + 8H2O

HV10O285- + 15H+

10VO2+ + 8H2O

V4O124- + 8H+

4VO2+ + 4H2O

HV2O73- + 5H+

2VO2+ + 3H2O

V2O74- + 6H+

2VO2+ + 3H2O

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Effect of the Aqueous Solution Compositionand Mechanism of V(V) Extraction (continue)

VO2SO4-(aq) + P+Cl-(PIM) [P+•VO2SO4

-](PIM) + Cl-(aq)

Yellow (pH 2.3) ----> Colorless after 2 h

VO2+ + SO4

2- VO2SO4

- (low rate reaction)

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Effect of the Aqueous Solution Compositionand Mechanism of V(V) Extraction (continue)

- The major V(V) species extracted is the VO2SO4-

- The breaking point observed at 1.3 suggested the extraction of other vanadium oxyanionsis possible

- Support for this hypothesis can be obtained by considering the mole fraction of VO2SO4-

(0.8) present in a solution at pH 2.3L.J. Lozano, C. Godínez, F.J. Alguacil, Hydrometallurgy 80 (2005) 196–202.

33

Back-extraction Studies

Nitric acid (3 mol L-1)

Hydrochloric acid (3 mol L-1)

Sulfuric acid (3 mol L-1)

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Optimization of the Back-extraction Solution Composition (continue)

(A) Hydrochloric acid (0.5 (○), 1.0 (×), 1.5 (▲), 3.0 (●), 4.5 (■) and 6.0 (♦) mol L-1)(B) Sulfuric acid (1.5 (▲), 3.0 (♦), 4.5 (■) and 6.0 (●) mol L-1).

[P+•VO2SO4-](PIM) + HSO4

-(aq) VO2SO4

-(aq) + P+HSO4

-(PIM)

VO2Cl2-

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Separation of V(V) and Mo(VI)

Mixture Metal ion Extraction Back-

extraction

Mix-1 V(V) 80.9 (±1.8) 80.7 (±2.8)

Mix-2 V(V) 59.6 (±1.4) 57.2 (±2.9)

Mo(VI) 98.6 (±0.2) 89.2 (±1.1)

Mix-3 V(V) 81.3 (±0.6) 80.3 (±2.6)

Al(III) 4.6 (±2.7) Not detected

Mix-4 V(V) 82.0 (±1.8) 81.3 (±2.6)

Co(II) Not detected Not detected

Mix-5 V(V) 81.0 (±2.0) 80.5 (±2.7)

Cu(II) Not detected Not detected

Mix-6 V(V) 80.4 (±2.8) 80.0 (±2.8)

Fe(III) Not detected Not detected

Mix-7 V(V) 81.2 (±1.9) 81.7 (±2.7)

Mn(II) Not detected Not detected

Mix-8 V(V) 81.7 (±2.4) 81.4 (±2.7)

Ni(II) Not detected Not detected

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Mix-9 V(V) 57.6 (±2.8) 56.8 (±2.8)

Mo(VI) 98.5 (±0.3) 92.1 (±0.6)

Al(III) Not detected Not detected

Co(II) Not detected Not detected

Cu(II) Not detected Not detected

Fe(III) Not detected Not detected

Mn(II) Not detected Not detected

Ni(II) Not detected Not detected

Separation of V(V) and Mo(VI) (continue)

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Separation of V(V) and Mo(VI) (continue)

Flowchart of the proposed two-step PIM-based process for the separation of Mo(VI) and V(V): Step I,selective and complete extraction of Mo(VI) at pH 1.1 and its subsequent back-extraction in a 6 M H2SO4

solution; Step II, extraction of V(V) at pH 2.3 (after pH adjustment) and its complete back-extractionusing a 6 M H2SO4 solution. PIM composed of 35 wt% Cyphos® IL 101, 10 wt% NPOE and 55 wt% PVDF-HFP. Feed solution: 50 mL of a 0.2 mol L-1 sulfate solution containing 50 mg L-1 of each of the followingions: V(V), Mo(VI), Al(III), Co(II), Cu(II), Fe(III) and Ni(II). Back-extraction solution: 50 mL of 6 mol L-1

sulfuric acid.

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Separation of V(V) and Mo(VI) (continue)

Metal ion

pH 1.1 (Step I) pH 2.3 (Step II)

Extraction Back-

extraction

Extraction Back-

extraction

V(V) Not detected Not detected 80.7 (±1.8) 79.2 (±2.7)

Mo(VI) 99.5 (±0.4) 97.9 (±2.8) Not detected Not detected

Al(III) Not detected Not detected Not detected Not detected

Co(II) Not detected Not detected Not detected Not detected

Cu(II) Not detected Not detected Not detected Not detected

Fe(III) Not detected Not detected Not detected Not detected

Mn(II) Not detected Not detected Not detected Not detected

Ni(II) Not detected Not detected Not detected Not detected

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Study of the PIM Stability

40

41

42

Part II

Application of the developed PIM in on-line separation followed by spectrophotometric determination of V(V) in a FIA system

43

● Recycling and recovery of heavy metals in the spent materials areconsidered in some extent before their reposition in theenvironment, the leakage of trace amounts of these toxic species isyet of important source for water and soil contaminations, andmenace the environment.

● Vanadium, as many other heavy metals, incorporated in a variety ofindustrial products which are influencing the human life. However,the residual of the spent products can be the source of vanadiumcontaminations.

● Beside the anthropogenic sources, it may be also entered to theenvironment by continental dust, marine aerosols, volcanicemissions, and the combustion of coal and petroleum crude oils.

V(V); Most Toxic Among Vanadium Species

44

● The role of vanadium, at trace levels, is known in biological systems,though at high concentration levels vanadium is considered to be atoxicant and hazard to the environment and human health.

● The International Agency for Research on Cancer has declared thatvanadium is possibly carcinogenic to humans. Toxicity of this metaldepends on its oxidation state, and it is known that the pentavalention is the most toxic among vanadium species.

● It has been studied that a concentration of 0.33 mg L-1 can beaccepted as safe limit for the presence of vanadium in drinking water.

V(V); Most Toxic Among Vanadium Species (continue)

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Analytical Methods Reported for V(V) Determination

● Electrochemical methods

● Inductively coupled plasma spectrometry

● Fluorescence Spectroscopy

● Gamma-ray spectroscopy

● Liquid chromatographic techniques

● Spectrophotometric methods

Advantages: Reliable, Sensitive, Simple, Low cost methodsDisadvantages: Non-selective attitude; Required a separation step

46

Separation Methods in Spectrophotometric Determinations

Liquid-liquid extraction

Liquid membrane techniquesBear the advantages of simultaneous extraction/back-extraction process

Supported liquid membrane AdvantagesLow amount of organic solvents and extractant requiredHigher surface area and faster mass transfer of the analyteDisadvantagesInstability resulted from the slow leaching of the membrane constituents

Polymer inclusion membranes Exhibit distinguished stability and versatility in comparison with other liquid membranes The polymer inclusion membranes made also possible the on-line extractive separation for selective determination of some ions

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FlAInexpensive automation of chemical analysis SimpleGreat convenience RapidLess consumption of reagents High accuracy

FIA/LLE, FIA/LM, FIA/SPEAllowed surmounting the difficulties encountered in direct quantitative determination of chemical species

FIA/PIMFirst application has been reported by Kolev’s GroupL.L. Zhang, R.W. Cattrall, M. Ashokkumar, S.D. Kolev, Talanta 97 (2012) 382-387

ObjectiveThe results obtained in the first part of this study convinced us for using a thinner PIM in an on-line extraction-separation and spectrophotometric determination of V(V) ions in a flow injection analysis (FIA) system. The suggested method was tested for determination of V(V) in water and pharmaceutical samples.

Flow Injection Analysis and Polymer Inclusion Membranes

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Flow Injection Analysis Manifold

Pump-1

R5

R4 Spectrophotometer

R3 (512 nm)

R2 Waste Waste

Donor channel Acceptor channel PC

R1 Membrane

Pump-2

Injection valve

Injection: 1000 mL of the sample solutionR1: Sodium sulfate (0.2 mol L-1) adjusted at pH 2.85R2: Second sodium sulfate streamStop-time: 10 min stop-timeR3: Acceptor stream (HCl 1 mol L-1)R4: Sodium hydroxide (1 mol L-1) for neutralization of the

acceptor solutionR5: Buffered solution (pH 5.35) and xylenol orange (0.01% w/v)Recond. time: 5 min

49

Investigated Parameters and Optimal Conditions

Parameter Verified range Optimal value

Stop-flow time of the acceptor stream 5-20 min 10 min

Sample volume 100-1000 mL 1000 mL

Carrier solution pH 1.25-3.25 2.85

Na2SO4 concentration in donor solution 0-0.5 mol L-1 0.2 mol L-1

Xylenol orange concentration 0.0025-0.0125 w/v% 0.01 w/v%

pH of the sample solution 1-7 1.5-6.0

Membrane thickness 35-130 mm 35 mm

Flow rates of donor solution (R1-R2) 0.09-0.41 mL min-1 0.19 mL min-1

Flow rates of acceptor solution (R3) 0.12-0.25 mL min-1 0.12 mL min-1

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Sample Volume and Stop-flow Time of the Acceptor Stream

0

0/04

0/08

0/12

0/16

0/2

0 5 10 15 20 25 30

Ab

sorb

ance

Stop-time (min)

1000 mL

500 mL

(a)

0

0/04

0/08

0/12

0/16

0/2

0 300 600 900 1200

Ab

sorb

ance

Sample volume (mL)

(b)

Variation of the absorbance as a function of (a) the acceptor stream stop-time and (b) the samplevolume for the determination of 3 mg L-1 of V(V). Experimental conditions: sample volume was 1000mL, membrane thickness of 35±6 mm. The flowrates of streams R1-R2 (Na2SO4 0.2 mol L-1, pH 2.35)and R3-R5 were 0.26 and 0.63 mL min-1, respectively. R3 hydrochloric acid 1 mol L-1, R4 sodiumhydroxide solutions 1 mol L-1 and R5 xylenol orange 0.005 w/v% in sodium acetate/acetic acid buffer(pH 5.35).

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pH and Sodium Sulfate Concentration of the Carrier Solution

0

0/04

0/08

0/12

0/16

0/2

0 1 2 3 4

Ab

sorb

ance

pH

(a)

0

0/04

0/08

0/12

0/16

0/2

0 0/2 0/4 0/6 0/8

Ab

sorb

ance

Sodium sulfate concentration (mol L-1)

(b)

Variation of the absorbance as a function of (a) the carrier solution pH and (b) the sodium sulfate

concentration in the carrier solution for the determination of 3 mg L-1 of V(V). Experimental conditions:

sample volume was 1000 mL, membrane thickness of 35±6 mm. The flowrates of streams R1-R2

(Na2SO4 0.2 mol L-1) and R3-R5 were 0.26 and 0.63 mL min-1, respectively. R3 hydrochloric acid 1 mol L-

1, R4 sodium hydroxide solutions 1 mol L-1 and R5 xylenol orange 0.005 w/v% in sodium acetate/acetic

acid buffer (pH 5.35).

VO2+ + HSO4

- VO2SO4

- + H+

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Xylenol Orange Concentration

0

0/04

0/08

0/12

0/16

0/2

0 0/005 0/01 0/015

Ab

sorb

ance

Xylenol orange (W/V%)

Variation of the absorbance as a function of the xylenol orange concentration for the determination of 3

mg L-1 of V(V). The concentration of sodium sulfate in the carrier solution was adjusted at 0.2 mol L-1.

Experimental conditions: sample volume was 1000 mL, membrane thickness of 35±6 mm. The flowrates of

streams R1-R2 (Na2SO4 0.2 mol L-1, pH 2.85) and R3-R5 were 0.26 and 0.63 mL min-1, respectively. R3

hydrochloric acid 1 mol L-1, R4 sodium hydroxide solutions 1 mol L-1 and R5 xylenol orange 0.005 w/v% in

sodium acetate/acetic acid buffer (pH 5.35).

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pH of the Sample Solutions

0

0/04

0/08

0/12

0/16

0/2

0 2 4 6 8

Ab

sorb

ance

Sample pH

Variation of the absorbance as a function of the sample solution pH for the determination of 3 mg L-1 of

vanadium(V). Experimental conditions: sample volume was 1000 mL, membrane thickness of 35±6 mm.

The flowrates of streams R1-R2 (Na2SO4 0.2 mol L-1, pH 2.85) and R3-R5 were 0.26 and 0.63 mL min-1,

respectively. R3 hydrochloric acid 1 mol L-1, R4 sodium hydroxide solutions 1 mol L-1 and R5 xylenol

orange 0.01 w/v% in sodium acetate/acetic acid buffer (pH 5.35).

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Membrane Thickness

0

0/04

0/08

0/12

0/16

0/2

0 30 60 90 120 150

Ab

sorb

ance

Membrane thickness (mm)

Variation of the absorbance as a function of the membrane thickness. Experimental conditions: sample

volume was 1000 mL, flowrates of streams R1-R2 (Na2SO4 0.2 mol L-1, pH 2.85) and R3-R5 were 0.26 and

0.63 mL min-1, respectively. R3 hydrochloric acid 1 mol L-1, R4 sodium hydroxide solutions 1 mol L-1 and

R5 xylenol orange 0.01 w/v% in sodium acetate/acetic acid buffer (pH 5.35).

Membrane thickness affects:- Membrane stability- Transfer rate

55

Flow Rate of Donor and Acceptor Streams

0

0/04

0/08

0/12

0/16

0/2

0 0/1 0/2 0/3 0/4 0/5

Ab

sorb

ance

R1+R2 flow rate (mL min-1)

(a)

0

0/04

0/08

0/12

0/16

0/2

0/24

0/28

0 0/1 0/2 0/3 0/4

Ab

sorb

ance

R3 flow rate (mL min-1)

(b)

Variation of the absorbance as a function of (a) the donor stream (R1-R2) and (b) the acceptor stream flow rates for the determination of 3 mg L-1 of vanadium(V). Experimental conditions: sample volume was 1000 mL, membrane thickness of 35±6 mm, R1-R2 Na2SO4 0.2 mol L-1 adjusted at pH 2.85), R3 hydrochloric acid 1 mol L-1, R4 sodium hydroxide solutions 1 mol L-1 and R5 xylenol orange 0.01 w/v% in sodium acetate/acetic acid buffer (pH 5.35).

Lower flow rates- Longer contact time of the sample zone with the membrane- Less efficient the transverse mixing because it relies on molecular diffusion.

S.D. Kolev, I.D. McKelvie, Advances in flow injection analysis and related techniques, Elsevier, 2008..

56

Analytical Figures of Merit

Linear calibration curve 0.5-8.0 mg L-1 of V(V)

Linear equation Abs.=0.083C

Correlation coefficient 0.9966

Limit of detection 0.08 mg L-1

RSD 2.9% (n = 8, V concentration 3 mg L-1)

PIM stability (RSD) 3.6% (n = 24, 3 days, V concentration 3 mg mL-1)

Sample rate analysis 4 h-1

57

Interference Study

Tested ions Maximum tested concentration(Binary mixtures with V(V) 3 mg L-1) (<5% error)

K(I) 150 mg L-1

Ca(II) 150 mg L-1

Mg(II) 150 mg L-1

Cd(II) 150 mg L-1

Co(II) 150 mg L-1

Mn(II) 150 mg L-1

Ni(II) 150 mg L-1

Zn(II) 150 mg L-1

Al(III) 50 mg L-1

Fe(III) 150 mg L-1

Chloride 150 mg L-1

Nitrate 100 mg L-1

Phosphate 150 mg L-1

Dichromate 50 mg L-1

Molybdate Interference (need to use off-line elimination)

58

Application of the Proposed Method

Sample Added/labelled

(mg L-1)/(mg/tablet)

Found* (mg L-1)

texp**FIA ICP

Tap water 1.00 0.97 (±0.06) 1.02 (±0.02) 0.91

2.00 1.95 (±0.07) 2.03 (±0.02) 1.35

Reservoir water 1.00 0.94 (±0.08) 1.03 (±0.03) 1.43

2.00 2.04 (±0.07) 2.02 (±0.01) 0.39

Pharmaceutical 1 1.00 0.93 (±0.08) 1.15 (±0.10) 2.45

Pharmaceutical 2 0.80 0.77 (±0.07) 0.83 (±0.05) 0.99

Pharmaceutical 3 0.095 0.089 (±0.006) 0.094 (±0.004) 1.12

*calculated based on three replicate experiments.** t-value at 95% confidence level and for four degrees of freedom is 2.78.

59

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Part III

Australian Universities& The University of Melbourne

61

62

Prof. Spas D. Kolev

Prof. Robert W. Cattrall(Honorary Professorial Fellow)

Dr. Ines Almeida(Research Fellow)

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