“Green analytical chemistry: Trace elemental analysis on ...web.uni-plovdiv.bg/kmetov/ACTIVITIES/BioSupport'Thermo(Plovdiv, 2012)A... · extractants and high enrichment factors

“Green analytical chemistry: Trace elemental analysis on water

samples by liquid-liquid microextration (LLME)-laser-

induced breakdown spectroscopy

5-6 June 2012, Plovdiv, Bulgaria

induced breakdown spectroscopy (LIBS)”

Hristina Nikolova, Miguel Angel Aguirre, Montserrat Hidalgo and Antonio Canals


Overview

� Introduction� Green chemistry

� Green analytical chemistry

� Sample preparation

� Miniaturization on sample preparation

� Liquid -liquid microextraction (LLME)


� Liquid -liquid microextraction (LLME)

� Detection techniques for LLME

� Laser-induced breakdown spectroscopy (LIBS) for trace elemental analysis

� Evaluating LIBS for the analysis of Mn in microdrop lets

� Direct microdroplets on aluminium substrates

� Testing the combination of LLME-LIBS: preliminary r esults

IntroductionIntroduction


IntroductionIntroduction

Introduction

‘‘Sustainable development’’‘‘Sustainable development’’

“protection of theenvironment’’

“protection of theenvironment’’

Green Chemistry


development’’development’’ environment’’environment’’

“a form of development that meets the needs of the present without compromising the ability of future

generations to meet their own needs’’

“a form of development that meets the needs of the present without compromising the ability of future

generations to meet their own needs’’

Introduction

“it is an unfortunate irony that environmentalanalytical methods often contribute to furtherenvironmental problems through the chemicals

“it is an unfortunate irony that environmentalanalytical methods often contribute to furtherenvironmental problems through the chemicals

Green Analytical Chemistry(I)


environmental problems through the chemicalsused in the analysis”environmental problems through the chemicalsused in the analysis”

From : P.T. Anastas, Crit. Rev. Anal. Chem., 29(3), 167-175 (1999)

Introduction

“The goal of Green Analytical Chemistry is touse analytical procedures that generate lesshazardous waste and that are safer to use and

“The goal of Green Analytical Chemistry is touse analytical procedures that generate lesshazardous waste and that are safer to use and

Green Analytical Chemistry(II)


hazardous waste and that are safer to use andmore benign to the environment”hazardous waste and that are safer to use andmore benign to the environment”

Introduction

Twelve Principles of Green Chemistry on Analytical Chemistry

� The elimination (or at least, the significant reduction) ofreagents, particularly organic solvents, from analyticalprocedures

� Reduced emissions of vapours and gases, as well as liquidand solid wastes generated in analytical laboratories

5-6 June 2012, Plovdiv, BulgariaFrom: M. Tobiszewski, A. Mechlinska, J. Namiesnik, C hem. Soc. Rev., 39, 2869–2878 (2010)

and solid wastes generated in analytical laboratories

� The elimination of highly toxic and/or eco-toxic reagents fromanalytical procedures (e.g., the substitution of benzene withother solvents)

� Reduced labour and energy consumption of analyticalprocedures (per single analyte)

� Reduced time gap between sampling and the desiredinformation becoming available (i.e., real time analysis)

Introduction

Challenges in Green Analytical Chemistry

5-6 June 2012, Plovdiv, BulgariaFrom: M.Tobiszewski, A. Mechlinska, J. Namiesnik, Ch em. Soc. Rev., 39, 2869–2878 (2010)

Introduction


Sample preparationSample preparation



Sample preparation

� Sample conditioning: Adapt the physical orchemical state to the requirements of theinstrument.

� Removal of interfering species: Masking orseparation techniques (e.g., adsorption,absorption, dialysis, precipitation, supercritical


absorption, dialysis, precipitation, supercriticalfluid extraction, liquid-liquid extraction (LLE),solid phase extraction (SPE), etc.)

� Additional operations: Dilution,(pre)concentration , chemical transformationsand derivatization, etc.

Sample preparation


Sample preparation is the Achilles’ Heel of total analytical process!!!!


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Publications

Sample preparation


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1000

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Solid phase extraction

Microextraction/m

iniaturization

Liquid-liquid extraction

Heating

Digestion

Mixing

Derivatization

Automation

Centrifugation

Filtration

Enrichment

Membrane extraction/dialysis

Drying

Precipitation

Homogenization

Stirring

Weighing

Headspace

Purge-trap

Evaporation

Organic extraction

Soxhlet extraction

Solid-liquid extraction

Supercritical fluid extraction

Cooling

Distilation

Therm

al desorption

Lixiviation

Combustion

Publications

(Source: SciFinder Scolar® 2010)

Sample preparation

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5-6 June 2012, Plovdiv, BulgariaSource: SciFinder ® (26/05/2012)

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Year

Classification of main extraction techniques:� Headspace extraction techniques:

� Static Headspace (SH)� Purge & Trap (dynamic headspace, P&T)

� Membrane extraction techniques

� Sorptive extraction techniques:

Sample preparation


� Solid-phase extraction (SPE)� Stir bar sorptive extraction (SBSE)� Solid-phase microextraction (SPME)

� Solvent extraction techniques:� Liquid-liquid extraction (LLE)� Liquid-liquid microextraction (LLME)

� Hollow fiber-liquid phase microextraction (HF-LPME)� Single drop microextraction (SDME)� Dispersive liquid-liquid microextraction (DLLME)

SDMESample preparation


Detection techniques for LLMEDetection techniques for LLME


Detection techniques for LLMEDetection techniques for LLME

Detection techniques for LLME

� Organic analytes

�HPLC, GC, CE before FID, ECD, UV-Vis, MS, etc.



� Inorganic analytes

�ETAAS, ETV-ICP-OES/MS, others (FAAS, CV-AFS,ICP-MS and ICP-OES)



THIS IS NOT PORTABLE INSTRUMENTATION!!!

Laser-induced breakdown spectroscopy (LIBS) for trace elemental analysis




LIBSLIBS� Disadvantage: low sensitivity �� high LODs

� Advantages: � Multielement analysis� Fast� Portability� Easy to automate


LLME and LIBS could be combined for trace metal analysis

LLME and LIBS could be combined for trace metal analysis

� Easy to automate� Capability to analyze very small

quantities (microdroplets) ofsample

Nd:YAGLaser

PC

2100 2120 2140 2160 2180 2200 2220

0

5x102

1x103

2x103

Inte

nsity

(a.u

.)

Wavelength (A)

Avantesspectrometer

Opticfiber

Micro-sample

Flashlamp

Q-Switch

Photodiode

� ns Nd:YAG laser (1064 nm)� Avantes modular spectrometer

(Czerny-turner configuration +CCD - covering from 300 nm –400 nm)

� Delay system (pulsegenerators) for acquisitiontime delay control

� Oscilloscope and photodiode

Evaluating LIBS for the analysis of Mn in microdrop lets


LIBS systemLIBS system


PulsegeneratorOscilloscope Pulse

generator

� Oscilloscope and photodiodeto monitor plasma formationand acquisition delay

� Synthetic samples with different Mn 2+ concentration were prepared� Microvolumes of the prepared samples were analyzed by using two different LIBS

experimental strategies:

� Analysis by direct laser irradiation of microdroplets� Analysis by laser irradiation of microdroplets on a metallic (aluminium) substrate

Experimental procedure Experimental procedure

Direct microdroplets on aluminium substrates

� 10 µL microdroplets were placed on analuminium substrate and left to dry for 15minutes

� Laser radiation was focused on the driedmicrodroplet to create the LIBS plasma

� Plasma emission was detected by theAvantes spectrometer

� Five spectra were taken for each singledroplet . Spectra of one single droplet

Aluminiumsubstrate

Focusing lens

Laser radiation

15 min

Sample microdroplets having differentMn2+ concentration

Plasma emission to AvaSpec


Experimental procedure Experimental procedure


droplet . Spectra of one single dropletwere averaged

LIBS emission signal markedlyimproves when microdropletsare analyzed by usingaluminium substrates.

Direct analysis of microdroplets vs.the use of aluminium substratesOrange spectrum corresponds to ananalyte concentration 10 times lowerthan that of green spectrum

258 259 260 261 2620

1x103

2x103

3x103

4x103

5x103

6x103

Inte

nsity

(co

unts

)

1% Mndirect analysis ofthe micro-droplet

Wavelength (nm)

0.1% Mnmicro-droplet on aluminum substrate

Mn

II (2

59.3

7nm

)

Mn

II (2

60.5

7nm

)

Since laser radiation can be focused on aextremely low sample area, thisconfiguration allows several replicatemeasurements to be carried out in a singlemicrodroplet.

Several laser shots on asingle, dried, 10 µLsample droplet

ResultsResults

Direct microdroplets on aluminium substrates

y = 321.22x + 0.03R2 = 0.9969

� Higher reproducibility and better linearity (R 2=0.9969 compared to direct analysis of droplets

� Limit of detection was found to be 6x10 -4 % ofMn (6 ppm)

Considering that microextractionmethodologies can lead to micro -volumes of


ResultsResults

0.0

0.1

0.2

0.3

0.4

(Mn

II)m/(

Al I

) m


Analysis of microdroplets on aluminiumsubstrates (Al was used as internal standard)

(a)

LIBS signal of a 10 ppm Mn sample

258 259 260 261 262

Blank (10% Triton)

Inte

nsity

(co

unts

)

Wavelength (nm)

10 ppm Mn

methodologies can lead to micro -volumes ofextractants and high enrichment factors(more than 200, in some cases)

LIBS analysis of microdroplets on solid substrates appears to be a promising alternative to be

combined with LLME methodologies for trace elemental analysis

LIBS analysis of microdroplets on solid substrates appears to be a promising alternative to be

combined with LLME methodologies for trace elemental analysis

0 2x10-4 4x10-4 6x10-4 8x10-4 1x10-3

0.0

Mn (%, w/w)


Testing the combination LLME-LIBS: preliminary resu lts

After SDMEAfter SDME DryingDrying LIBS analysisLIBS analysis


Focusing lens

Mirror

Spectrometer

LIBSplasma

Optical system



Univariate optimizationUnivariate optimization

�Molar ratio (APDC/analytes)


VariablesVariables

�Molar ratio (APDC/analytes)�pH�Extraction time�Stirring speed�Droplet volume


VariableVariable

ConstantsConstants

�pH = 10�Extraction time = 10 min

Molar ratio (APDC/analytes)



ConstantsConstants�Extraction time = 10 min�Stirring speed = 1700 r.p.m.�Droplet volume = 5 µL

0

10000

20000

30000

40000

50000

60000

70000

80000

0 5 10

Inte

nsity

(a.u

.)

Molar ratio

CuI 324.754



0

10000

20000

30000

40000

50000

60000

70000

80000

0 5 10

Inte

nsity

(a.u

.)

CuI 324.754

05000

100001500020000250003000035000400004500050000

0 5 10

Inte

nsity

(a.u

.)

MnII 259.373

0100020003000400050006000700080009000

10000

0 5 10

Inte

nsity

(a.u

.)

ZnII 206.200


0

2000

4000

6000

8000

10000

12000

14000

0 5 10

Inte

nsity

(a.u

.)

Molar ratio

CrI 357.869

0 5 10Molar ratio

0 5 10Molar ratio

0

500

1000

1500

2000

2500

3000

3500

0 5 10

Inte

nsity

(a.u

.)

Molar ratio

NiI 352.454

0 5 10Molar ratio



VariableVariable

ConstantsConstants

�Molar ratio (APDC/analytes) = 5�Extraction time = 10 min

pH


ConstantsConstants�Extraction time = 10 min�Stirring speed = 1700 r.p.m.�Droplet volume = 5 µL

0

10000

20000

30000

40000

50000

60000

70000

0 5 10 15

Inte

nsity

(a.u

.)

pH

CuI 324.754



0

10000

20000

30000

40000

50000

60000

70000

0 5 10 15

Inte

nsity

(a.u

.)

ZnII 206.200

0

20000

40000

60000

80000

100000

120000

0 5 10 15

Inte

nsity

(a.u

.)

MnII 259.373

0

10000

20000

30000

40000

50000

60000

70000

0 5 10 15

Inte

nsity

(a.u

.)

CuI 324.754


0 5 10 15pH

0 5 10 15

pH

0 5 10 15pH

0

2000

4000

6000

8000

10000

12000

0 5 10 15

Inte

nsity

(a.u

.)

pH

NiI 352.454

0

10000

20000

30000

40000

50000

60000

70000

0 5 10 15

Inte

nsity

(a.u

.)

pH

CrI 357.869

pH 10 pH 12



VariableVariable

ConstantsConstants

�Molar ratio (APDC/analytes) = 5�pH = 10

Extraction time


ConstantsConstants�pH = 10�Stirring speed = 1700 r.p.m.�Droplet volume = 5 µL

0

5000

10000

15000

20000

25000

30000

35000

40000

0 5 10 15

Inte

nsity

(a.u

.)

Time (min)

CuI 324.754

0

2000

4000

6000

8000

10000

12000

0 5 10 15

Inte

nsity

(a.u

.)

ZnII 206.200



0

10000

20000

30000

40000

50000

60000

70000

80000

0 5 10 15In

tens

ity(a

.u.)

MnII 259.373

0

5000

10000

15000

20000

25000

30000

35000

40000

0 5 10 15

Inte

nsity

(a.u

.)

CuI 324.754


0 5 10 15Time (min)

0 5 10 15

Time (min)

0 5 10 15Time (min)

0

200

400

600

800

1000

1200

1400

1600

1800

0 5 10 15

Inte

nsity

(a.u

.)

Time (min)

NiI 352.454

0

200

400

600

800

1000

1200

1400

1600

1800

0 5 10 15

Inte

nsity

(a.u

.)

Time (min)

CrI 357.869



VariableVariable

ConstantsConstants

Stirring speed



ConstantsConstants�pH = 10�Extraction time = 10 min�Droplet volume = 5 µL

0

10000

20000

30000

40000

50000

60000

70000

0 500 1000 1500 2000

Inte

nsity

(a.u

.)

rpm

CuI 324.754



0

5000

10000

15000

20000

25000

0 1000 2000

Inte

nsity

(a.u

.)

ZnII 206.200

0

10000

20000

30000

40000

50000

60000

70000

0 1000 2000

Inte

nsity

(a.u

.)

MnII 259.373

0

10000

20000

30000

40000

50000

60000

70000

0 1000 2000

Inte

nsity

(a.u

.)

CuI 324.754


0 1000 2000

rpm

0 1000 2000rpm

0 1000 2000

rpm

0

1000

2000

3000

4000

5000

6000

0 1000 2000

Inte

nsity

(a.u

.)

rpm

NiI 352.454

02000400060008000

100001200014000160001800020000

0 1000 2000

Inte

nsity

(a.u

.)

rpm

CrI 357.869



VariableVariable

ConstantsConstants

Droplet volume



ConstantsConstants�pH = 10�Extraction time = 10 min�Stirring speed = 1700 r.p.m.

0

5000

10000

15000

20000

25000

30000

35000

40000

0 5 10 15

Inte

nsity

(a.u

.)

Droplet volume (µL)

CuI 324.754



0

5000

10000

15000

20000

25000

0 5 10 15

Inte

nsity

(a.u

.)

ZnII 206.200

0

10000

20000

30000

40000

50000

60000

70000

0 5 10 15

Inte

nsity

(a.u

.)

MnII 259.373

0

5000

10000

15000

20000

25000

30000

35000

40000

0 5 10 15

Inte

nsity

(a.u

.)

CuI 324.754


0 5 10 15


0 5 10 15Droplet volume (µL)

0 5 10 15Droplet volume (µL)

0

1000

2000

3000

4000

5000

6000

7000

0 5 10 15

Inte

nsity

(a.u

.)


NiI 352.454

0

2000

4000

6000

8000

10000

12000

14000

0 5 10 15

Inte

nsity

(a.u

.)


CrI 357.869



Optimized valuesOptimized values


�Molar ratio (APDC/analytes) = 5�pH = 10�Extraction time = 10 min�Stirring speed = 1700 r.p.m.�Droplet volume = 7.5 µL



ZnII 206.200 nmZnII 206.200 nm


Without SDME

With SDME

Blank100 ppb500 ppb1000 ppb


Without SDME With SDME

Emission line (nm) Slope (ppb-1) LOD (ppb) Slope (ppb-1) LOD (ppb)

ZnII (206.200) 7.6±0.4 171 54±3 23



ZnII (206.200) 7.6±0.4 171 54±3 23MnII (259.373) 29±4 427 59±4 301CuI (324.754) 26±5 141 55±5 54NiI (352.454) 2.0±0.2 149 11.3±0.6 67CrI (357.869) 7.0±1.0 143 17.6±1.2 50

Acknowledgments

Conclusions

I. For the first time, the capability for elementalanalysis of LLME + LIBS has beenexperimentally proved

Conclusions


II. Nevertheless, much work is still needed inorder to definitively assess the analyticalcapabilities of LIBS to be coupled withseveral microextraction methodologies

Future workFuture work

� Study and optimization of the best solid substrate tobe used as solid-sample holder

� Study of the influence of the extraction solvent(concentration and nature – surfactants, ionic liquids,

Future work


(concentration and nature – surfactants, ionic liquids,organic solvents, etc.) on LIBS signal

� Study of the double pulse LIBS methodology as amean to obtain further emission intensity and S/Nenhancement

� Miniaturized/portable LIBS system

Acknowledgments

Acknowledgements

I. The Spanish Government (projects CTQ2008-06730-C02-01 and CTQ2011-23968)

II. NSF of Bulgaria (GAMA project DO 02-70)

Acknowledgements


II. NSF of Bulgaria (GAMA project DO 02-70)

III. European Union Seventh FrameworkProgramme (FP7). Program Capacities(REGPOT). BioSupport project

The SP-BG team


The BG-SP team


Thank you

for

Thank you

for


your

attention

your

attention

Documents

“Green analytical chemistry: Trace elemental analysis on ...web.uni-plovdiv.bg/kmetov/ACTIVITIES/BioSupport'Thermo(Plovdiv, 2012)A... · extractants and high enrichment factors