Adsorptive Stripping Voltammetry of Environmental Carcinogens

Current Analytical Chemistry, 2008, 4, 000-000

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Adsorptive Stripping Voltammetry of Environmental Carcinogens Jiri Barek*, Karolina Peckova, and Vlastimil Vyskocil Charles University in Prague, Faculty of Science, Department of Analytical Chemistry, UNESCO Laboratory of Environmental Electrochemistry, CZ 128 43 Prague 2; Czech Republic Abstract: This review describes our recent results regarding adsorptive stripping voltammetric determination of submicromolar and nanomolar concentrations of various environmentally important chemical carcinogens using both traditional (hanging mercury drop electrode, carbon paste electrode) and non-traditional types of electrodes (solid amalgam electrodes, glassy carbon paste electrodes, carbon ink film electrodes, solid composite electrodes). The review concentrates on our own results in the context of the general development in the filed.

Keywords: Adsorptive stripping voltammetry, chemical carcinogens, hanging mercury drop electrode, solid amalgam electrodes, carbon paste electrodes, solid composite electrodes. Dedicated to the memory of Professor Jaroslav Heyrovsk on the occasion of 85th anniversary of the invention of polarography. 1. INTRODUCTION Cancer exacts substantial costs in treatment and preventive measures on a world-wide scale and causes immeasurable human suffering. The approximately 20% cancer mortality together with the fact that environmental causes contribute to the majority of cancers emphasizes the potential benefits of environmental detection of chemical carcinogens and raises carcinogenic substances monitoring in general and working environment to the highest priority [1,2]. Analytical measurement procedures should have a critical role in molecular epidemiology and exposure regulation, as well as in environmental monitoring. Determination of trace amounts of chemical carcinogens is a challenging task for modern analytical chemistry because it is necessary to determine extremely low concentrations of those dangerous substances in rather complex matrices. Moreover, great structural variability of chemical carcinogens requires a great variability of applied analytical methods. Nowadays, modern separation techniques (e.g. gas chromatography, high performance liquid chromatography or capillary zone electrophoresis) or spectrometric techniques (e.g. mass spectrometry or fluorescence techniques) are most frequently used for these purposes. However, these methods are characterized by high investment and running costs. On the other side, modern polarographic and voltammetric methods are much cheaper even though in some cases they can satisfy high demands on sensitivity required for the determination of environmental carcinogens and thus be a viable alternative to more frequently used spectrometric or separation methods [3]. According to our experience [4-6], modern polarographic and voltammetric methods, e.g. differential pulse polarography/voltammetry (DPP/DPV) [7,8] or high performance liquid chromatography with electrochemical detection (HPLC*Address correspondence to this author at the Charles University in Prague, Faculty of Science, Department of Analytical Chemistry, UNESCO Laboratory of Environmental Electrochemistry, CZ 128 43 Prague 2; Czech Republic; Tel: +420 221 951 224; Fax: +420 224 913 538; E-mail: [email protected]

1573-4110/08 $55.00+.00

ED) [9] are among those fulfilling the stringent conditions on selectivity and sensitivity essential in the determination of chemical carcinogens. Moreover, sensitivity of voltammetric methods can be further increased by adsorptive accumulation of determined substances at the surface of the working electrode using so called adsorptive stripping voltammetry (AdSV) [10-15]. Our earlier results regarding the determination of nanomolar concentrations of chemical carcinogens using modern polarographic, voltammetric and amperometric techniques were summarized in our previous reviews [46]. Therefore, in this review we concentrate on our recent results obtained in this decade. 2. HISTORY AND PRINCIPLES OF ADSORPTIVE STRIPPING VOLTAMMETRY Classical DC polarography on classical dropping mercury electrode (DME) developed by professor Heyrovsk 85 years ago is not sensitive enough from the point of view of present requirements regarding the monitoring of environmental carcinogens. Its modern variations based on efficient suppression of undesirable effects of charging current (DPP, DPV, etc.) reach limit of detection around 10-7 mol.L-1. Thus, they must be combined with preliminary separation and preconcentration (most frequently by liquid liquid extraction (LLE) or solid phase extraction (SPE)) to reach nanomolar or subnanomolar concentration region requested for analysis of chemical carcinogens. Nevertheless, in this combination they can be successfully used for determination of trace amounts of chemical carcinogens in various environmental matrices, i.e. in highly polluted water from Vltava river in the centre of Prague. The surface of DME is periodically renewed with every new drop formed which diminishes problems connected with the passivation of the electrode surface with substances present in this complex environmental matrix. Therefore, DPP at DME is our choice for analysis of heavily polluted waters even though the limit of determination (LOD) is practically one order of magnitude higher then for DPV at hanging mercury drop electrode (HMDE) and several orders of magnitude higher then for AdSV at HMDE [4-6]. © 2008 Bentham Science Publishers Ltd.

2 Current Analytical Chemistry, 2008, Vol. 4, No. 3

The later method uses the accumulation of the determined substance onto the surface of working electrode to increase the sensitivity of the voltammetric determination. For the determination of heavy toxic metals, electrochemical accumulation is mainly used and so called anodic stripping voltammetry is frequently used in recent environmental analysis. For organic compounds there is another possibility for their accumulation and that is adsorption. This was firstly demonstrated by Kalvoda [16,17] during studies connected with alternating current oscillographic polarography. In the fifties of the last century he was the first one to recognize the possibility to increase the sensitivity of oscillographic polarography via an adsorptive accumulation of an analyte at a mercury electrode. However, in practice, this principle began to be exploited in late eighties of the last century when improved versions of HMDE appeared on the market. This type of electrode was originally developed by outstanding Polish electrochemist Wiktor Kemula [18] and it is extremely useful for AdSV. The use of this electrode together with the introduction of period of potentiostatic accumulation during „quiescent period“ has resulted in AdSV as it is used nowadays [19,20]. More then two thousand publications on AdSV together with excellent reviews [10-15,21] confirm its important position among trace electroanalytical methods. AdSV is characterized by the use of a suitable stationary electrode and by the exact control of time used for adsorptive accumulation of the test substance at the electrode/solution interphase. This preconcentration step is followed by voltammetric determination of the adsorbed substance. Many organic substances exhibit surface active properties that are manifested by their adsorption from measured solution onto the surface of a suitable chosen working electrode resulting in the formation of an adsorbed layer of molecular dimensions. At the given temperature, the amount of adsorbed substance depends on its concentration in the solution, on the structure of the substance, material and surface conditions of the electrode, composition of the analyzed solution and the time of accumulation (if the complete coverage of the electrode is not achieved). AdSV can be utilized for the determination of substances that are readily adsorbed on the working electrode, e.g. compounds characterized by a poor solubility in aqueous supporting electrolytes such as aromatic, polyaromatic and heterocyclic compounds. If the adsorbed substance contains a functional group that can undergo a faradayic process at the electrode, it can be easily detected by subsequent stripping step. The most frequently used potential program for this stripping step is DCV, DPV, square wave voltammetry (SWV) or phase sensitive AC technique i.e. the stripping step is carried out under potentiostatic control. However, it is possible to use adsorptive accumulation followed by a galvanostatic stripping step, the corresponding technique being called constant current stripping analysis, adsorptive potentiometry, potentiometric stripping analysis or in accordance with IUPAC nomenclature adsorptive stripping chronopotentiometry (AdSCP). Although AdSCP is remarkably less sensitive to interferences due to surface active impurities, it is still less frequently used in the analysis of chemical carcinogens. For critical comparison of scope and limitation of AdSV and AdSCP see excellent review of Kalvoda [22]. For electroinactive substances, only a

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tensametric signal is detected, which is usually less sensitive and it is rarely used in the analysis of chemical carcinogens. 3. WORKING ELECTRODES USED IN ADSORPTIVE STRIPPING VOLTAMMETRY OF CHEMICAL CARCINOGENS In general, any working electrode applicable in voltammetry can be used in AdSV as well if a constant, wellreproducible surface can be assured throughout the whole measurement cycle or even better throughout the whole series of measurements. Obviously, different working electrodes fulfill this requirement in different degree. According to our experience, HMDE is the best one for AdSV determination of reducible chemical carcinogens as demonstrated by selected examples in Table 1 and by reviews [3-6]. AdSV at HMDE is by far the most sensitive method. However, it is less robust and more prone to interferences from surface active substances and other compounds likely to be present in river or surface water. Thus it should be used mainly for analysis of relatively clean samples (e.g. of drinking water) or of samples after their preliminary clean-up or preliminary separation. Extremely high sensitivity of AdSV at HMDE is demonstrated by Fig. (1). Solid amalgam electrodes, namely polished silver solid amalgam electrode (p-AgSAE) or mercury meniscus modified silver solid amalgam electrode (m-AgSAE) [5,23,24] are applicable as well, even though they gave somewhat higher LOD. They present a non-toxic, “green” alternative to HMDE the application of which is complicated by – according to our opinion unsubstantiated – fears of mercury toxicity. Both the selectivity and the sensitivity of AdSV at AgSAE can be increased by preliminary separation and preconcentration using LLE or SPE [25] which enables determination of nanomolar concentrations of electrochemically reducible chemical carcinogens. Because the surface of mAgSAE is not so easily renewable as the surface of HMDE, an electrochemical pre-treatment was proposed to eliminate problems with electrode passivation. Regeneration lasting about 30 s before each measurement is carried out by periodical switching every 0.1 s between potentials at least 100 mV more negative than the potential of amalgam dissolution (Eini ) and at least 100 mV more positive than the potential of hydrogen evolution (Efin) in the used base electrolyte. Regeneration always ends at more negative potential. The optimum values of Eini and Efin are to be found experimentally as the values leading to most stable signal values in repeated measurements. The appropriate values of the potential and the time of regeneration were inserted in the program (software utility) of the used computer-controlled instrumentation so that the regeneration of the m-AgSAE was always carried out automatically. The applicability of m-AgSAE for the determination of trace amounts of chemical carcinogens is demonstrated by Fig. (2). Bismuth electrodes present another very promising alternative to mercury electrodes for AdSV of electrochemically reducible substances [26]. However, their application on the determination of environmental carcinogens remains to be investigated.

Adsorptive Stripping Voltammetry of Environmental Carcinogens

Current Analytical Chemistry, 2008, Vol. 4, No. 3

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Fig. (1). AdS voltammograms of 2,7-dinitro-9-fluorenone in methanol – Britton-Robinson buffer pH 11 (1:9) medium measured by AdSV at HMDE, S = 1.45 mm2, Eacc = -300 mV and tacc = 60 s; c(2,7-dinitro-9-fluorenone): 0 (1), 210-9 (2), 410-9 (3), 610-9 (4), 810-9 (5), 10109 (6) mol·L-1. The corresponding calibration straight line is in the inset.

However, we have recently successfully used carbon powder based films on traditional solid electrodes as an alternative to disposable electrodes [29] for DPV of both reducible and oxidizable carcinogens. The application of those carbon ink film electrodes for AdSV of those substances is recently investigated with promising preliminary results.

Fig. (2). AdS voltammograms of carcinogenic 3-nitrofluoranthene in methanol – 0.01M NaOH (1:1); tacc = 15 s; Eacc = -350 mV; Eini = -350 mV and Efin = -1600 mV. c(3-nitrofluoranthene): 0 (1), 210-8 (2), 410-8 (3), 610-8 (4), 810-8 (5), 1010-8 (6) mol.L -1.

The same is valid for solid graphite composite electrodes, prepared by polymerization of graphite - epoxide mixture [5,27,28], which were successfully used for DPV of both oxidizable and reducible carcinogens. Their application for AdSV of those substances is under investigation in our laboratory. Carbon paste electrodes (CPE), which are very suitable for AdSV of electrochemically oxidizable carcinogens, are not too useful for AdSV of electrochemically reducible carcinogens because of problems of removing oxygen contained in a paste which gives large and broad interfering peak.

The most frequently used electrodes for AdSV of electrochemically oxidizable substances are bare or chemically modified carbon paste electrodes [30]. From 2001 several reviews appeared covering the monitoring of environmental carcinogens with the use of CPE (together with other types of electrodes) [31-34]. There are many types of unmodified carbon pastes differing by the pasting liquids and the carbon powder used [5,30]. Bare carbon pastes are well suited for AdSV determination of oxidizable chemical carcinogens, namely those containing OH or NH2 group on an aromatic or heterocyclic skeleton [3]. Carbon pastes based on classical spectrographic carbon powders and paraffin, silicon or mineral oils as binders were used in the past predominantly in aqueous media or mixed media with low amounts of organic modifiers as higher content of e.g. methanol or acetonitrile quickly degraded the pastes. The introduction of globular particles [35] and glassy carbon spherical microparticles [36] resulted in pastes compatible with organic solvents which can be used for AdSV determination of chemical carcinogens. The main reason to modify an electrode is to obtain qualitatively new sensor with desired, often pre-defined properties. Regarding this, carbon pastes undoubtedly represent one of the most convenient materials for the preparation of modified electrodes. In contrast to relatively complicated modifications of solid substrates, the preparation of chemically modified CPE (CMCPE) is very simple. Modifier can be dissolved directly in the pasting liquid or admixed mechanically to the paste during its homogenisation. It is also possible to soak graphite particles with a solution of a modi-


fier, and after evaporation of the solvent, use thus prepared impregnated carbon powder. Finally, already-prepared pastes can be modified in situ. From the point of view of AdSV, the most useful function of a modifier is preferential entrapment of desired species leading to higher selectivity and sensitivity [30].Selected applications of AdSV at CPE for determination of submicromolar concentrations of chemical carcinogens are given in Table 1. 4. METHODOLOGICAL REMARKS The proper choice of the base electrolyte is of extreme importance in AdSV. In many cases, it is necessary to use mixture of aqueous buffer with a suitable organic solvent because of the limited solubility of test substances in water. For the determination of extremely low concentrations of chemical carcinogens, 10- or 100-fold diluted buffer or other base electrolyte used yields a smoother curve of the supporting electrolyte due to lower concentrations of trace impurities in the chemicals used for its preparation. It is advisable to decrease the concentration of organic solvent as low as possible, because its presence usually decreases the tendency of organic substances to adsorb on the surface of HMDE or of any other working electrode. Optimization of conditions for AdSV determination of chemical carcinogens is usually based on examination of influence of pH and the composition of the base electrolyte on the position, height and shape of voltammetric curves. The most important is the influence of pH which effects not only electrochemical behavior of determined chemical carcinogens but also its adsorptive properties. Generally, more polar species, such as protonated carcinogenic aromatic amines or dissociated aromatic hydroxy compounds, are less easily adsorbed and are more easily dissolved in polar solvents. From this point of view, neutral less polar species have stronger tendency for adsorption than charged cationic or anionic species and thus pH at which these species prevail in the solution is optimal for their AdSV determination Therefore, the usual procedure is based on the investigation of the influence of pH in the range of pH 2-12 which reveal at which pH we can obtain highest, best developed and most easily evaluable voltammetric responses. The potential of accumulation is another important parameter. Uncharged species are usually best adsorbed at mercury electrodes at potentials around electrocapillary zero, because at potentials far away from these potentials either anions or cations of the base electrolyte are electrostatically attracted towards mercury electrode thus expelling adsorbed neutral species. The height of peaks understandably increases with increasing time of accumulation until the maximum possible coverage of the working electrode. Afterwards, the signal does not further increase with the time of accumulation. Optimal potential and time of accumulation are usually determined experimentally. The influence of the potential program used for stripping process was already discussed earlier. 5. CHEMICAL CARCINOGENS DETERMINABLE BY ADSORPTIVE STRIPPING VOLTAMMETRY Overall evaluations of chemical carcinogens can be found on web pages of International Agency for Research on

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Cancer (IARC) [37]. If you compare the list of carcinogenic substances with the review of electrochemically active organic functional groups [38] you can see the wide applicability of modern polarographic and voltammetric techniques in the analysis of chemical carcinogens. The most important groups of chemical carcinogens containing electrochemically reducible functional groups and thus amenable to AdSV determination using HMDE or mAgSAE are nitrated polycyclic aromatic hydrocarbons, heterocyclic compounds, azo compounds, mycotoxins, and antitumour drugs. The last mentioned substances are mentioned here because they are frequently genotoxic and can enter the environment via hospital waste waters thus presenting quite interesting environmental problem. Among carcinogenic substances containing electrochemically oxidizable functional groups which can be determined by AdSV at carbon paste electrodes, carbon film electrodes, screen printed electrodes or composite elctrodes are aromatic or heterocyclic amines and substances containing OH group on aromatic or heterocyclic system, namely metabolites of many environmental carcinogens and anitumour drugs which can be used for biological monitoring of human exposure to those substances. The selected examples of adsorptive stripping voltammetric determination of various chemical carcinogens recently developed in our UNESCO Laboratory of Environmental Electrochemistry are summarized in Table 1. CONCLUSIONS Low investment and running costs predestine AdSV for large scale monitoring of electrochemically active chemical carcinogens. It is worth mentioning that electrochemically inactive compounds do not interfere with AdSV unless they are surface active, so that it is possible to determine e.g. easily reducible carcinogenic nitrated polycyclic aromatic hydrocarbons in the presence or non-reducible parent polycyclic aromatic hydrocarbons or carcinogenic azo compounds in the presence of parent aromatic amines. Although selectivity of these methods is lower than that of modern separation techniques especially combined with MS detection, it is in many cases sufficient for practical purposes. If we do not see corresponding AdSV signal in an environmental sample and this signal can be clearly seen after standard addition of trace amounts of the analyte, we can be pretty sure that this substance is not present in the sample at a concentration corresponding to this standard addition. Thus we can use AdSV as a screening method and only in those cases in which the presence of monitored substance cannot be ruled out, we will use more powerful but simultaneously more expensive, more complex and more time-consuming techniques. However, these cases represent minority of all cases because in most cases electroanalytical techniques are sufficient to prove the absence of monitored substance. However, if there is a peak at potential corresponding to a monitored substance, we cannot be 100% sure that it corresponds to the substance. It can correspond to some interferent having coincidentally the same peak potential as our analyte. In that case we should use some more powerful but much more expensive techniques, most frequently hyphenated ones. But it is necessary to stress that the same hold for


Table 1.

Current Analytical Chemistry, 2008, Vol. 4, No. 3

Selected Determinations of Environmental Carcinogens Using Adsorptive Stripping Voltammetry

Analyte

Technique

Supporting electrolyte

Eacc mV

tacc s

LOD a mol·L-1

Ref.

2-Acetamidofluorene

AdS DPV / CPE

BR buffer pH 7

0

60

4·10-8

39

2-Aminoanthraquinone

2-Aminobiphenyl

3-Aminofluoranthene

AdS DCV / HMDE

-50

600

3·10

AdS DPV / HMDE

-50

60

3·10-8

AdSV / -CDM CPEb

0

180

2·10-8

AdSV / -CDM CPEc

0

180

1·10-9

0

180

1·10-8

AdSV / -CDP-SPEe

0

180

1·10-9

AdSV / -CDPA-SPEf

0

180

7·10-10

350

300

4·10-7

-150

120

2·10-8

0

200

2·10-7

AdSV / -CDM CPEb

0

180

9·10-9

AdSV / -CDM CPEc

0

180

5·10-9

0

180

1·10-8

AdSV / -CDP-SPEe

0

180

9·10-9

AdSV / -CDPA-SPEf

0

180

9·10-9

AdSV / -CDM CPEb

0

180

2·10-8

AdSV / -CDM CPEc

0

180

9·10-9

0

180

2·10-8

AdSV / -CDP-SPEe

0

180

3·10-9

AdSV / -CDPA-SPEf

0

180

2·10-10

200

180

1·10-7

44

180

1·10

-7

45

-7

45

AdSV / -CDM CPEd

AdSV / GCE

BR buffer pH 2 - methanol (99:1)

BR buffer pH 7


AdSV / CPE 2-Aminofluorene

1-Aminonaphthalene

2-Aminonaphthalene

1-Aminopyrene 3-Aminoquinoline

-9

AdSV / CPE

AdSV / -CDM CPEd

AdSV / -CDM CPEd

AdSV / GCPE AdSV / CPE

BR buffer pH 12

BR buffer pH 9

BR buffer pH 9

BR buffer pH 2 - methanol (9:1) 0.1 M H3 PO4

200

40

41

42 43

41

41

5-Aminoquinoline

AdSV / CPE

0.1 M H3 PO4

200

180

5·10

6-Aminoquinoline

AdSV / CPE

0.1 M H3 PO4

200

180

1·10-7

45

180

2·10

-7

46

-7

8-Aminoquinoline 1,2-Diaminoanthraquinone

AdSV / CPE AdS DCV / CPE

0.1 M NaOH BR buffer pH 12 - methanol (9:1)

AdS DPV / CPE

0 0

180

2·10

0

180

2·10-8

47

2,7-Diaminofluorene

AdSV / CPE

BR buffer pH 12

0

200

1·10-7

43

N,N-Dimethyl-4-amino-4 'hydroxyazobenzene

AdSV / GCPE


0

300

2·10-8

48

2,7-Dinitro-9-fluorenone

AdSV / HMDE


-300

60

4·10-9

49

1,3-Dinitronaphthalene

AdSV / HMDE

BR buffer pH 12

-200

120

2·10

-9

50,51

-8

50,52


AdSV / HMDE

0.01 M NaOH

-250

30

2·10


AdSV / HMDE

0.01 M NaOH

-450

120

2·10-8

50

-8

53

Doxorubicin

m-AgSAE

BR buffer pH 6

-350

60

9·10

5


Barek et al.

(Table 1) contd....

Analyte

Technique

Supporting electrolyte

AdS DCV / CPE

Eacc mV

tacc s

LOD a mol·L-1

0

120

1·10-7

0

120

2·10-9

BR buffer pH 7

AdS DPV / CPE

54

9-Fluorenol

AdS SWV / CPE

0.1 M H2 SO4

0

60

1·10-6

39

2-Methyl-4,6-dinitrophenol

AdSV / HMDE

BR buffer pH 6

-50

60

1·10-9

55,56

-8

6-Methyl-5-nitroquinoline 1-Naphthylamine

AdSV / HMDE


-200

30

2·10

0.01 M NaOH - methanol (99:1)

-200

30

2·10-8

0.01 M NaOH

0

180

8·10-8 -9

59,60

AdSV / CDM CPEg

57 58

2-Nitrobiphenyl

AdSV / HMDE


-400

180

3·10

3-Nitrobiphenyl

AdSV / HMDE


-400

600

2·10-9

59,60

600

3·10

-9

59,60

-9

42,61

4-Nitrobiphenyl 3-Nitrofluoranthene

5-Nitroindazole 1-Nitronaphthalene 2-Nitronaphthalene

AdSV / HMDE


8-Nitroquinoline b

-400

AdSV / HMDE


-200

1200

5·10

AdSV / m-AgSAE


-350

15

3·10-8 -8

AdSV / HMDE AdSV / HMDE

42, 24,62

0.1 M H3 PO4

-75

60

2·10

0.01 M NaOH

0

180

1·10-8

0.001 M LiOH

-400

300

2·10-9

64,65

-9

64,66

AdSV / HMDE

0.001 M LiOH

-400

120

2·10

AdSV / HMDE

ten-fold diluted BR buffer pH 12 methanol (9:1)

-200

180

1·10-8

AdSV / HMDE

ten-fold diluted BR buffer pH 2 - methanol (99:1)

0

600

1·10

-9

AdSV / HMDE

0.002 M LiOH - methanol (9:1)

-250

40

2·10-8

1-Nitropyrene

a

Ref.

c

63

67

68

limit of determination; -cyclodextrine modified carbon paste electrode; -cyclodextrine modified carbon paste electrode; -cyclodextrine modified carbon paste electrode; ecyclodextrine condensation polymer modified carbon-based screen-printed electrode; fcarboxymethylated -cyclodextrine condensation polymer modified carbon-based screenprinted electrode; gdimethyl--cyclodextrine modified carbon paste electrode

chromatographic techniques, where the agreement of retention time alone is not a sufficient proof of identity. From the point of view of trace analysis of environmental chemical carcinogens it should be stressed that AdSV is an independent alternative capable to confirm the results of separation and spectrometric methods “beyond reasonable doubt” which is important from legal point of view because in complex cases two or even three independent methods are requested to be used.

d

in certain cases can successfully compete with modern spectrometric and separation techniques or can supplement them. ACKNOWLEDGEMENT This research was supported by the Ministry of Education, Youth and Sports of the Czech Republic (project LC 06035 and MSM 0021620857) LIST OF ABBREVIATIONS

According to our opinion, for some electrochemically active chemical carcinogens and some types of matrices, AdSV may be the "best method". Moreover, in many other cases, AdSV can be among “fit for the purpose” methods. It means it can give the same results as other more expensive and more complex methods. Combination with preliminary separation and preconcentration can increase both the selectivity and the sensitivity of those methods to fulfill stringent demands of environmental analytical chemistry.

AdSCP

= Adsorptive stripping chronopotentiometry

AdSV

= Adsorptive stripping voltammetry

CMCPE

= Chemically modified carbon paste electrode

CPE

= Carbon paste electrode

DCV

= Direct current voltammetry

DME

= Dropping mercury electrode

We believe that AdSV will continue to be very useful analytical tool in the analysis of chemical carcinogens, which

DPP

= Differential pulse polarography

DPV

= Differential pulse voltammetry


Eacc

=

Potential of accumulation

HMDE

= Hanging mercury drop electrode

HPLC-ED = High performance liquid chromatography with electrochemical detection GCPE

= Glassy carbon paste electrode

GCE

= Glassy carbon electrode

LLE

= Liquid-liquid extraction

LOD

= Limit of determination

Current Analytical Chemistry, 2008, Vol. 4, No. 3 [27] [28] [29] [30] [31] [32] [33] [34]

m-AgSAE = Meniscus modified silver solid amalgam electrode

[35]

p-AgSAE = Polished silver solid amalgam electrode

[36]

SPE

= Solid phase extraction

[37]

SWV

= Square-wave voltammetry

[38]

tacc

=

Time of accumulation

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8 Current Analytical Chemistry, 2008, Vol. 4, No. 3 [67]

Barek, J.; Zima, J.; Moreira, J.C.; Zima, J.; Muck, A. Collect. Czech Chem. Commun., 2000, 65, 1888.

Received: ??????????????

Revised: ???????????

Accepted: ?????????????

Barek et al. [68]

Kolarova, J. Diploma Thesis, Charles University in Prague, Prague, 2002.