Electroanalytical Chemistry

(1)

Quo Vadis

Electroanalytical Chemistry

Jiri Barek

UNESCO Laboratory of Environmental Electrochemistry, Department of Analytical Chemistry, Charles University,

Prague, Czech Republic

,

e-mail: Barek@natur.cuni.cz

(2)

UNESCO Laboratory of

Environmental Electrochemistry

Charles University in Prague

Heyrovský Institute AS CR

(3)

UNESCO Laboratory of

Environmental Electrochemistry

• Established by the decision of the XXIInd UNESCO General Conference in 1983

• Joint research facility of the J. Heyrovsky

Institute of Physical Chemistry, Academy of Sciences of the Czech Republic and the

Department of Analytical Chemistry, Faculty of Science, Charles University, Prague

• Oriented towards solving both theoretical

and practical problems of environmental

electrochemistry

(4)

Professor Jaroslav Heyrovský

(5)

Chem. Listy 16 (6), 256 (1922)

(6)

ULEEC internationally recognized

• ACD IUPAC, orange book

• DAC EuChEMS Euroanalysis

• Tessaloniky 17TH INTERNATIONAL

CONFERENCE ON CHEMISTRY AND THE ENVIRONMENT 16-20 June, 2019

• ESEAC Rhodos Vilnius

• ECTN Label Committee

• Invited lectures/Scientific committees

• Honorary membership of foreign chemical

societies

(7)

International Cooperation

(8)

Analytical chemistry provides the methods and tools

needed for insight into our material world…for answering four basic questions about a material sample:

•What?

•Where?

•How much?

•What arrangement, structure, or form?

Federation of European Chemical Societies, Karl Cammann, Univ. Muenster, 1992

Fresenius’ Z. Anal. Chem., 343 (1992) 812

Measure what is measurable and

make measurable what is not

(9)

Time Information

content

“…omics”

complex mixture

mixture

1 compound location 1 d

2 d 3 d

1/h 1/min 1/s continuously

Space

Increasing information needs

1000 000 higher information densities in few years

Pushing trends-new principles, theories, instrumentation, grant agency policies

Pulling trends new problems, single

molecule and macromolecule analysis

analysis,

(10)

Development of analytical methods Push

New

• Principles

• Theories

•Instruments Policy of

grant

agencies

Pull

New

problems The main task of basic

academic research is to satisfy our curiosity and to search for

something unexpected Curiosity driven research

Heureka vs It is funny

Joy of reasoning and understanding is the most beuatiful gift of nature

A.E.

(11)

Pull

• Health services

Clinical analysis – EU- 3 billions of analysis/year - 1 % GDP

• Environmental analysis

• Food and drinks (Agriculture)

• Economic competition

• Nano a Bio technologies

• Information technologies

• LRI

(12)

Pull

1. Time and space resolved analysis 2. Single molecule analysis

3. Trace analysis in complicated organic and biological matrices down to ppb 4. Identification of macromolecules and

microorganisms

5. Implantable sensors (controlled dosing,

continuous monitoring, long-distance

transfer of data)

(13)

Pár čísel úvodem

• 5% ekonomie EU přímo závisí na výsledcích analýz

• pro 20% evropských chemiků je analýza hlavní náplní práce

• pro 50% evropských chemiků je analýza nejvýznamnější vedlejší náplní práce

• v EU je prováděno více než 5 miliard vsádkových analýz ročně, počet dat z kontinuálních analýz je astronomický a většinu z nich nikdo nezpracovává

• ročně je produkována více než 100,000 analytických publikací

• skoro polovina legislativy by nefungovala bez výsledků chemických analýz

• řízení moderní společnosti je nemyslitelné bez analytické chemie

• M. Grasserbauer - Analytical chemistry is

indispensable to democratic governance

(14)

•Pestrost problémů vyžaduje pestrost metod

• Neexistuje nejlepší analytická metoda

• O volbě metody budou rozhodovat důvody:

 Ekonomické (pořizovací a provozní náklady)

 Parametrové (citlivost, selektivita, LOD)

 Praktické (robustnost, spolehlivost,

jednoduchost,časová a experimentální náročnost, uživatelská přívětivost

 Legislativní

Co se musíme pamatovat

(15)

No co musíme připravit studenty

• Obrovské počty analýz (knihovny látek, genomika, proteomika, evironmentální analýza = velkoplošné monitorování)

• Měření v neobvyklých matricích (sliny, sperma, krev z pupeční šňůry, mozkomíšní mok)

• Odpovídat na otázky přesahující tradiční představu o analytické chemii

• Biomonitoring

• Akreditace, validace,….

• Někdy v dobré víře připravujeme spíše na minulost

• Kam kráčí analytická chemie JML

(16)

Co neumí absolventi vysokých škol chemického zaměření

Základy matematiky, fyziky, chemie Pohybovat se v chemické laboratoři Napsat krátkou zprávu

Připravit jednoduchý rozpočet

Vysvětlit laborantům co mají dělat

Akreditaci, validaci, práci s normami

Pozdravit

(17)

Zdá-li se vám vzdělání příliš drahé, vyzkoušejte kolik stojí

nevzdělanost

Paradigm of solid electrodes

“God made solids,

but surfaces were the work of the devil”

Wolfgang Pauli

(18)

It is my wish that this country was the most educated in the world, therefore I hereby direct that all my subjects were awarded a doctorate.

Visionary cartoon from newspaper around 1960.

Is there an escape from the „trap“

of the massive higher education?

(19)

Čím reaguje analytická chemie na tyto podněty

• Drahé, mimořádně účinné, citlivé a selektivní metody,

založené na různých kombinovaných technikách (GC-MS, HPLC-MS, CZE-MS, MS-MS, ICP-MS)

• Středně drahé techniky pro více méně rutinní analýzy (GC, HPLC, CZE, AAS, FIA, SIA, BIA, DPV, AdSV aj.)

• Levné techniky použitelné i pro velkoplošné monitorování (disposabilní sensory, barevné papírky, atp).

• Lab on chip

• Lab on valve

• Lab o paper

• Lab on mmbrane

 Výchova nových odborníků!

 Nám chybí post doc

(20)

Žijeme v období technického zdokonalování starých principů

Mění se paradigma trojhvězdí věda výzkum výuka

Co jsme znali my

Co znají dnešní studenti

Není možné všemu rozumět

Za 1femtosekundu světlo uleti 3 mikrometry O 1 nm povyroste můj fous než si k tváři

zvednu holicí strojek

(21)

Period of technical

improvement of old ideas

Is there any objective evaluation?

Diploma Thesis1870 Microelectrodes 1930

Refused patent application 1930 Amalgam electrodes 1940

RIA

Waste of money for

atomic weights determination instrument

John Fenn Tanaka

(22)

Ida Henrietta Hyde (1857-1945)

Harward Medical School

Microelectrodes

(23)

VIA

Voltammetric imunoassay

Solomon Berson Rosalyn Yalow

Nature 184, 1648 (1959)

(24)

Main Works

Flexible Tape Electrode Biomass-Derived

Macroporous

Carbon Materials

(25)

MPA

FSDPV

(26)

(27)

Implanted biosensors

(28)

Screen-printing a 3D tisk

(29)

WE

CE

RL Mic

ABAC

Android based analytical chemistry

(30)

Paper-Based Microfluidic Sampling for Potentiometric/Voltametric Ion Sensing

Paper acts as a sampling unit and a

sample container

Paper provides a well-defined

thin aqueous layer

(31)

Lab on CD

(32)

Paper-based

electroanalytical platform - lab-on-paper

low cost

rapid response

potential portability allowing on-site measurements and decentralized

measurements

simple fabrication and handling green analytical chemistry Paul Anastas

(33)

www.bvt.cz

Sensors

(34)

FLOW SYSTEMS

Well-defined hydrodynamics

(35)

Present position of electroanalytical chemistry

• Lambda sensors in cars 10 G$

• pH measurement potentiometry 2 G$

• Electrochemical detection of glucose 1G$

• Monitoring of dionized watter 0.5 G $

• Fischer titration

• Nanotechnologie T $ Richard Feynman

"There's Plenty of Room at the Bottom,"

Caltech 29.12.1959.

• There is plenty of room in the middle and at the

top

(36)

Falen taboos

• Voltammmetry in the absence of supporting electrolyte

• HPLC-ED with gradient elution

• Diamond electrodes

• CPE in organic solvents

• RDE in one drop of solution

• Voltammetry without solvent (Dick McCreery – dry electrochemistry –nitrobifenyl,

• Tubular detector for HPLC

• Wireles electrochemistry

• ABEC Instrument-less electrochemistry

(37)

3 POINTS vs SWOT

• TECHNIQUES

V(DPV, SWV. AdSV) A (HPLC, FIA, SIA, BIA) M (AFM, EIS,SEM)

• ELECTRODES / columns/detectors

Metallic (Hg,Bi,Sb)

Amalgam (Solid, Paste, Single Crystal

)

Carbonaceous (CPE, CFE, BDDFE)

• ANALYTES

• Biomarkers (illness, exposition, treatment)

• Environmental pollutants (carcinogens, pesticides, drugs)

• Food components (carcinogens, antioxidants, dyes)

(38)

Why electrochemical methods POSSIBILITIES

• Large LDR and low LOD

• Broad spectrum of analytes

• Low runing and investment cost

• Speed and automatization

• Dimensionality

• Particle is direct source of signal

• Independet alternative

• Selectivity

• Miniaturization and portability

• Response factor

(39)

Why electrochemical methods LIMITATIONS

• We must know what we are looking for

• Analyte must be electrochemically active

• Problems with interferences

• Problems with matrix

• Problems with passivation

• Problems with validation

• Problems with education

• Problems with manufacturer support

(40)

Recent trends vs SWOT

1. New electrode materials

2. Chemically modified electrodes 3. Biologically modified electrodes 4. MIPS

5. Nanoparticle modified electrodes 6. Miniaturization

7. Automation

8. Simplification

9. Flow measurements

10.Combination with sep and spftm

(41)

1. New electrode materials

S

• Better electrochemical parameters

• Resistance to passivation

• Mechanical stability

• User and environmentally friendly W

• Inertia and resistance of practical laboratories

• Fashion vs usefulness

O

• Never-ending story

• Fascinating possibilities of material engineering T

• Lack of really critical comparison

• Pressure for innovativeness complicate thorough testing, validation, etc.

(42)

Mercury electrodes

Advantages

•Atomically smotth surface

•Easy renewal

•Large cathodic window

Disadvantages

•Narow anodic window

•Mechanical stability

•Toxicity

(43)

Why new electrode materials

• Broader potential window

• Lower noise and background current

• Resistance toward passivation

• Mechanical stability

• Compatibility with „green analytical chemistry“

Which new electrode materials

• Amalgams

• Diamond films

• Carbon films

• Sputtered metal films

(44)

Amalgam electrodes

(45)

Miniaturized Electrode System for Microtiter Plate

 m-AgSAE working electrode

 Ag/AgCl reference electrode (1 mol l

^–1

KCl)

 platinum auxiliary electrode

3 cm 3 mm

(46)

Silver amalgam paste

Pasting liquids

• mineral oil (44:1)

• paraffin oil (20:1)

• silicone oil (15:1)

• tricresylphosphate (11:1) Ag₃Hg₂

(47)

Pipette tip

Metal wire (contact) Paste amalgam (11% Ag)

Silver Paste Amalgam Electrode

(48)

AgSAE microelectrodes

(A)Silver amalgam crystals at mercury drop,

(B) single needle crystal of silver amalgam (magnification 200x)

(C) working electrode based on single crystal of silver amalgam (magnification 50x)

(49)

SCAgAE

Contact - Pt wire 20 μl pipette tip 10 % Ag silver amalgam paste

Single crystal of silver amalgam Polystyrene film

(50)

Carbon paste electrodes

• Introduced by Adams

• Easy preparation

• Easily renewable surface

• Reasonable potential window in anodic region, mechanical stability, noise,

• Tunable properties

• Easy covering with Hg or Bi film

• Easy chemical and biological modification

• Problems with oxygen

• Problems with organic solvents

(51)

CPE based on glassy carbon microbeads compatible with organic solvents

V = 1 ml V = 0.1 ml V = 10 ml

(52)

Carbon fibre rod electrode

(53)

Carbon Film Electrode

• The carbon film electrode (CFE) was made by covering silver amalgam electrode

(AgSAE) by carbon film.

•The film was prepared by immersing AgSAE‘s surface to an ink

solution.

•The ink solution was prepared by mixing carbon powder with polystyrene in

dichlorethane.

(54)

Carbon Film Electrode

The benefits of CFE are:

• Broad potential window (cca +1.5 to -1.5 V)

• Aplicability of electrochemical pretreatment to ensure repeatability of measurement

• Possibility of easy renewal of the film, when the old one is passived

• Possibility of the use of the original electrode after wipping off the film

• Low price of film

• Any solid electrode can be used for covering by the film

• More „green“ than disposable electrodes

• Suitable for HPLCE-ED in WJ arrangement

(55)

Carbon film electrodes at AgSAE

(56)

Carbon film cels in microtitration plate´s holes

(57)

CFE embeded in wells of

microtitration plates

(58)

Carbon film electrodes on

alumina sheed or on CD disk

Spot electrodes on glass or polymer

(59)

(60)

0.05 g L^–1 Bi³⁺ solution in 1 mol L^–1 acetate buffer pH 4.8

AgSAE BiF electrodeposition BiF-AgSAE

Bi³⁺

Bi³⁺ Bi³⁺

Bi³⁺ Bi³⁺ Bi³⁺

stirring / oxygen removed deposition potential –1.2 V

deposition time 5 min

disc diameter 0.5 mm

Bismuth Film Electrode

• Suitable for the concept of “green” analytical chemistry

• Increased sensitivity of determination in comparison to AgSAE

(61)

Bulk bizmuth minielectrode

(62)

Bismuth miniaturized electrode

system

(63)

Bi MES + microtitration plate

(64)

Polymer or glass decorated by metal nanoparticles-

nanostructured surface

SEM

Deposition:

Sputtering

Evaporation

(65)

Nanostructured electrodes

Au

Pd Ag

(66)

(67)

BORON DOPED DIAMOND FILM ELECTRODES

• Low noise

• Broad potential windows

• Low passivation

• Mechanical and electrochemical stability

• Biocompatibility

• Comercial availability

(68)

CVD - Chemical Vapor Deposition

Boron doped diamond film electrode

(69)

(70)

Boron doped diamond film electrode (BDDFE)

2

3 4

6 7 5

1

8

Legend

1. Electrode body 2. Screw contact 3. Screw attachment 4. Small metal spring 5. Brassy sheet

6. DFE on Si (1,1,1) 7. Silicone seal

8. Access for solution

Surface of nanocrystalline diamond film electrode on Si

(71)

BDDFE

Lab made Commercial

Glass tube (1), copper wire (2), conductive epoxide resin (3), non-conductive epoxide resin (4), silica wafer covered with BDDF (5)

(72)

BDDFE

(73)

2. Chemically modified electrodes

S

• Higher selectivity and sensitivity W

• Lower stability and reproducibility

• Complicated preparation

O

• Broad research field with many possibilities T

• Autotelic

• Lost of purpose

(74)

0.05 g L^–1 Bi³⁺ solution in 1 mol L^–1 acetate buffer pH 4.8

AgSAE BiF electrodeposition BiF-AgSAE

Bi³⁺

Bi³⁺ Bi³⁺

Bi³⁺ Bi³⁺ Bi³⁺

stirring / oxygen removed deposition potential –1.2 V

deposition time 5 min

disc diameter 0.5 mm

Bismuth Film Electrode

• Suitable for the concept of “green” analytical chemistry

• Increased sensitivity of determination in comparison to AgSAE

(75)

SbFE at substrates AgE AuE CuE GCE

Potential of depozition: –800 mV

Concentration of Sb

³⁺

: 40 mg·l

^–1

in 0.1M HCl

Time of depozition: 90 s

(76)

3. Biologically modified electrodes

S

• High sensitivity and selectivity

• Predictable response

W

• Complicated preparation

• Lower robustness, reliability O

• Bright future see glass electrode T

• Problems with commercialization

(77)

SAM - self assembled monolayer (method)

EDC - N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride NHS - N-hydroxysuccinimide

GOx - glucose oxidase

Enzyme immibilization on porous AgSAE

(78)

CFE DNA immobilization DNA/CFE

DNA

DNA DNA

DNA DNA DNA

carbon film disc diameter 7.0 mm

Fabrication of DNA Biosensor

accumulation potential +0.5 V ● accumulation time 1 min ● stirring

10 mg mL^–1 DNA in 0.1 mol L^–1 phosphate buffer of pH 7.0 (PB)

(79)

0 5 10 15 20 25 30 0

20 40 60 80 100

Relative biosensor response, %

Incubation time, min

I_p,c I_p,a

-100 0 100 200 300 400 500

-80 -60 -40 -20 0 20 40 60 80

I, µA

E, mV CFE

DNA/CFE 1 min 3 min 5 min 10 min 20 min 30 min

Evaluation of DNA Damage

Current density 50 mA cm^–2

CV

0 150 300 450 600 750 900

0 100 200 300

-Z '',

Z ', 

CFE DNA/CFE 1 min 3 min 5 min 10 min 20 min 30 min

0 5 10 15 20 25 30

0 20 40 60 80 100

EIS

Current density 50 mA cm^–2

(80)

0.0 0.5 1.0 1.5 0

10 20 30 40 50 60

I, µA

E, V

DNA/CFE 1 min 3 min 5 min 10 min 20 min 30 min

0 5 10 15 20 25 30

0 20 40 60 80

100 10 mA cm^-2

50 mA cm^-2

Evaluation of DNA Damage

SWV

50 mA cm^–2

Similar observation as in the case of DNA damage caused by Fenton-like reaction

Two antagonistic phenomena

↓ oxidation of DNA bases  decreasing number of active guanosine moieties

↑ opening of DNA helix  increasing number of active guanosine moieties

(81)

4. MIPS

S

• High selectivity and sensitivity

• Better stability

W

• Promises not completely fulfilled so far O

• Nearly unlimited possibilities for research

• MIOS for nanoparticles

T

• High resistance of polymer

• Necessity to produce very thin layers

(82)

5. Nanoparticle modified electrodes

S

• High sensitivity and selectivity W

• Reproducibility - one batch vs different batches

• Trial and error approach vs knowledge based prediction approach

O

• Endless possibilities, combinations, etc.

T

• Toxicity of nanoparticles

(83)

CPE modified with carbon nanoparticles

Modification of the working electrode surface by dropcasting of nanomaterial solution in

DMF (2mg/mL) on the electrode surface.

After drying and evaporation of the organic solvent, thin layers of the carbon

nanomaterials were deposited on the

electrode surface on which the oxidation of the target analyte take place.

SWCNT > MWCNT > Graphene > Fulerene

(84)

DP voltammograms HVA

at non-modified CPE in BRB pH 2.0

^{(2) 1.10}^-6^{(3) 2.10}^-6^{, (4) 3.10}^-6^{, (5) 4.10}^-6^{, (6) 5.10}^-6^{, (7) 6.10}^-6^{, (8) 7.10}^-6^{, (9)}

8.10^-6, (10) 9.10^-6, (11) 10.10^-6 mol.l^-1.

The pulse amplitude and scan rate are 50 mV and 50 mV.s^-1.

(85)

DP voltammograms HVA at SWCNTs surface modified CPE in BRB pH 2.0

^{(1) 1.10}^-6^{(2) 2.10}^-6^{, (3) 3.10}^-6^{, (4) 4.10}^-6^{, (5) 5.10}^-6^{, (6) 6.10}^-6^,

(7) 7.10^-6, (8) 8.10^-6, (9) 9.10^-6, (10) 10.10^-6 mol.l^-1.

The pulse amplitude and scan rate are 50 mV and 50 mV.s^-1

(86)

DP voltammograms HVA at MWCNTs surface modified CPE in BRB pH 2.0

^{(1) 1.10}^-6^{(2) 2.10}^-6^{, (3) 3.10}^-6^{, (4) 4.10}^-6^{, (5) 5.10}^-6^{, (6) 6.10}^-6^{, (7)}

7.10^-6, (8) 8.10^-6, (9) 9.10^-6, (10) 10.10^-6 mol.l^-1.

The pulse amplitude and scan rate are 50 mV and 50 mV.s-1.

(87)

6. Miniaturization

S

• More green, less expensive

• Lower amount of sample

• Portable –field application – point of care devices W

• Les user friendly so far

O

• Increasing demand

T

• Extreme miniaturization

(88)

(89)

Measurement in one drop of

solution

(90)

• Working electrode: GCE or PtE

• Reference electrode: Silver wire

• Auxiliary electrode: Platinum wire

• 20 µl 250 µl

Measurements in one drop and in Eppendorf vial

(91)

Micro-Volume Voltammetric Cell

1.

• Simplified scheme of

a micro-volume voltammetric cell

(92)

SC AgSAE Minielectrode

Micro-vial

PTFE capillary Mini-reference

electrode

Single crystal of silver amalgam Pt wire

(Auxiliary electrode)

Insulator

(Polystyrene film) Pipette

Pipette tip

Pt wire (contact)

Micro-vial

PTFE capillary Mini-reference electrode

Single crystal of silver amalgam Pt wire

(Auxiliary electrode)

Insulator (Polystyrene film)

Pipette

Pipette tip Pt wire (contact)

(93)

Miniaturizized CPE

Metal capillary + plastic tip + plastic pipette tip

+ glass tip

(94)

Multisensor (8 minielectrodes)

1 - m-AgSAE 2 - MF-AgSAE 3 - p-AgSAE 4 - p-CuSAE 5 - m-CuSAE 6 – AuE (gold electrode)

7 – PtE (Platinum electrode

8 – GCE (glassy carbon electrode)

9 – Pt – auxiliary E

(95)

7. Automation

S

• High throughput – large scale monitoring

• Lower labour cost

• Lower danger of human errors W

• Higher investment cost

• More difficult improvisation

• Sometimes higher degree of expertise required O

• Ever increasing demands T

• Sometimes too practical for basic research

• Robotics vs FIA

(96)

8. Simplification

S

• Lower cost

• More user friendly

• Lower problems

W

• Acceptability of simplified procedures O

• Broad field for creative electrochemists T

• Uncertain definition of simplicity

If you make the method more „idioteproof“

someone will invent a better idiot

(97)

9. Flow measurements

S

• Decreased time of analysis (FIA)

• Increased selectivity (HPLC ED)

• lower passivation

W

• More complicated instrumentation

• More complicated optimization O

• Easy automation

• Increasing demand for large scale monitoring

T

• Better experts needed

(98)

Why to measure in flowing systems

• To decrease time of analysis

batch system →flow system (FIA)

• To increase selectivity

combination of ED with HPLC or CZE

• Additional advantege – lower

passivation

(99)

Why electrochemical detection

• Broad LDR and low LOD

• Broad spectrum of analytes

• Low running and investment costs

• Molecule of an analyte is a direct source of a signal

• Independent alternative

• Higher selectivity

(100)

HPLC-ED-HMDE

• Higher selectivity

• Lower sensitivity

• LOD  10

^-5

M

• User unfriendly

• Mechanically unstable

• Azo, nitro, nitroso

(101)

Combined TL and WJ arrangement Carbon fibre detector

Thin-layer Wall-jet Tubular

(102)

HPLC-ED

Microcylindrical detector

Tubular detector

12, 39 (2000)

(103)

HPLC-ED carbon fibre detector

(104)

BDDFE Thin – Layer Detector

1-AN a 1-AB (5.10^-6 M) DFE(a) a GCE(b)

(105)

Tubular detector TD-AgSA)

Teflon capillary (ID1=0.5 mm, OD1=1.6 mm,ID2=1.6 mm, OD2=3.1 mm

Column of AgSAE (ID1, OD1, L=6.0 mm), .

(106)

SC AgSAE Flow-trough cell

HPLC

Outlet to

overflow vessel with immersed

Reference electrode

Crystallic silver amalgam

(Working electrode) Pt wire (Auxiliary electrode) PTFE tube

(107)

Glassy Carbon Microbeads

Renewable Electrochemical Detector

(108)

Carbon felt detector FIA ED HPLC ED

1 – inlet; 2 – screw with flat ferula; 3 – cap; 4 – carbon felt; 5 – outlet; 6 –

platinum electrical contact.

planar carbonaceous material orderless carbon fibers

three-dimensional structure

(109)

FIA ED on BDDFE

Lab on chip

(110)

SIA - ED - BDD

Lab on valve

(111)

Two-dimensional electrochemical detection

• Fast scanning of the potential range – complete three- dimensional response;

• Combination with flow injection analysis – rapid way for obtaining complete voltammograms

Determination of capsaicin in chili peppers – three

injections in approx. 30 s

(112)

10.Combination with sep and spftm

S

• Increased selectivity

W

• Increased complexity

O

• New horizons

• Complete solutions offered T

• More complex method development

• Broder expertise required

(113)

Hollow fibre microextraction

(114)

MY WISH

Czech Republic

(115)

Thank you for your attention

(116)