Journal of Solid State Electrochemistry

, Volume 12, Issue 10, pp 1185–1204

Modified carbon-containing electrodes in stripping voltammetry of metals

Part I. Glassy carbon and carbon paste electrodes

Authors

    • Ural State University of Economy
  • Natalya A. Malakhova
    • Ural State University of Economy
  • Mikhail V. Fyodorov
    • Ural State University of Economy
  • Khiena Z. Brainina
    • Ural State University of Economy
Open AccessReview Paper

DOI: 10.1007/s10008-007-0472-4

Cite this article as:
Stozhko, N.Y., Malakhova, N.A., Fyodorov, M.V. et al. J Solid State Electrochem (2008) 12: 1185. doi:10.1007/s10008-007-0472-4

Abstract

Papers dealing with modified electrodes made of carbon materials and composites for use in stripping voltammetry of metals have been reviewed. The review consists of two parts, of which the first considers applications of modified glassy carbon and carbon paste electrodes, while the second describes diverse modified carbon-containing composite and microscopic electrodes. Information about modifiers, electrode modification methods, conditions, and limits of detection of elements in different materials has been tabulated. The review covers 550 papers published in Russia and abroad between 1990 and the first half of 2007.

Keywords

Modified electrodes Glassy carbon Carbon paste electrodes Stripping Voltammetry Metal ions determination

Introduction

Voltammetry is one of the most universal methods of electroanalytical chemistry, which is widely used as a technique for measurement of concentrations of substances and as a tool for analysis of their properties. The growing number of papers concerned with problems and urgent issues of voltammetry is indicative of the increasing interest among chemists to this method. The general status and future trends of voltammetry and electrochemical sensors are described in the reviews [17]. A priority line of its development that follows from the analysis of those papers is the creation, the study and the use of new electrodes, electrochemical sensors [8], transducers, and detectors for automated, flow-through, and “field” analysis. This is because the electrochemical signal is formed by processes taking place on the electrode surface. Therefore, the condition of the electrode surface, which depends on the origin, the defect content, and the mechanical inhomogeneity of the material, determines many significant quantitative characteristics of electrochemical measurement systems. Required electrochemical properties of the electrode can be obtained if its surface is modified purposefully. Therefore, the modification and the “molecular design” of the transducer surface and the formation of grafted layers on solid surfaces constitute an actively developing new area of investigation. Problems of the chemical modification of solid surfaces, specific and regular features of the modifier attachment to various solid matrices, and examples of practical applications of chemical sensors (modified electrodes) are overviewed in the papers [921].

Over a period of years, the development of the voltammetric method was connected with metal, primarily mercury, electrodes. But mercury is an extremely toxic material. This element presents the first-rate hazard leading to severe poisoning and heavy diseases. For this reason, some countries (USA, Japan, EC) have declared a moratorium on the use of mercury in storage batteries, lamps, thermometers, pesticides, etc. Electrodes made of nontoxic materials also tend to smoothly force out mercury electrodes in electroanalysis. As an alternative to toxic mercury electrodes, electrodes of a nontoxic “dental” amalgam (Ag2Hg3 with the surplus silver; [22, 23]) have been developed and used for measurements of heavy metals. Carbon materials (CMs) possessing some attractive features [24, 25] are widely used as mercury-free current-conducting electrode materials. Firstly, depending on the CM type, the character of the electrical conduction can change from the metal to the semiconductor conduction suggesting broad potentials for a wide range of capacitive, adsorption, catalytic, and kinetic properties. Secondly, the carbon surface can adsorb a variety of compounds by both the nonspecific physical sorption and the specific chemisorption with a functional coating, which can be formed either under the forced action of reagents or due to the presence of native functional groups resulting from a thermomechanical treatment of the material [25, 26]. Thirdly, the complexation capacity of carbon materials is higher than that of metals. Fourthly, CMs can form strong covalent bonds with some surface modifiers favoring the development of modified electrodes. Fifthly, the carbon surface is electrochemically inert over a wide interval of potentials. All these features predetermine the use of diverse carbon materials in electroanalysis. Glassy carbon, pyrolytic graphite, carbon glass-ceramics, impregnated graphite, carbon fibers, filaments, cloths, gauzes, and composite materials serve as the electrode material. The properties of CM electrodes, their specific features and drawbacks, and applications in voltammetric measurements of substances are described in the Russian reviews published in 1988 and 1990 [27, 28]. The present overview covers papers published in Russia and abroad since 1990. To narrow the borders of an extensive literature stream on modified carbon-containing electrodes for the 17-year period, the current review has been restricted on a method of analysis and analyte. So, the electrodes used for metal ion determination with SV have been described only. All the papers published over this period can be divided into six main groups depending on the type of the electrode used: glassy carbon (GCE), carbon paste (CPE), carbon-containing composite (CCE), impregnated graphite (IGE), thick-film graphite-containing (TFGE) electrodes, carbon microelectrodes (CME), and their arrays (ACME). As Fig. 1 suggests, GCE is the first with respect to the number of papers published over the 15 years. The minimum number of papers, most of which have appeared recently, are dedicated to TFGE and CME. This is due to the fact that these two groups of the electrodes represent recently emerging and vigorously developing lines of research into the use of carbon-containing electrodes.
https://static-content.springer.com/image/art%3A10.1007%2Fs10008-007-0472-4/MediaObjects/10008_2007_472_Fig1_HTML.gif
Fig. 1

Representation of papers published in 1990–2005 depending on electrode type described

Glassy-carbon electrodes

Glassy carbon is isotropic, is almost gas-tight, has low porosity, is very hard, is a good current conductor, and is stable in many corrosive media [25]. The adsorptivity and the reactivity of glassy carbon are low compared to those of other structured graphite materials having a hexagonal or a rhombohedral lattice. These factors account for the low sensitivity of unmodified glassy-carbon electrodes in analysis [2934]. The detection limit of elements is reduced by increasing the electrochemical accumulation time (up to 40 min) [3542], using additional accumulation operations, e.g., the ultrasonic extraction [43] or modifying the GCE surface.

Table 1 shows some applications of modified GCE for voltammetric measurements of inorganic ions [44190]. Methods of the preliminary modification of the surface (ex situ) and the in-analysis modification (in situ) are widely used for the purposeful transformation of the GCE surface properties. These methods are sometimes combined to enhance the selectivity. For example, a film of a metal or a current-conducting polymer is applied to GCE and a selective organic reagent or mercury, gold, or bismuth ions, which co-precipitate with the element to be determined, are added to the solution. GC is a preferable substrate for mercury film electrodes [191]. In this case, the two-layer modification of the surface is realized by the “ex situ/in situ” scheme. On occasion, up to three modified layers each, having its specific application and certain function, are built up on the surface. For example, the layer-by-layer modification by a clay mineral, a cation-exchange cross-linked polymer and mercury [156] results in that the GCE surface forms a layer, which possesses cation-exchange properties, can form an amalgam, and separates coarse molecules or cations.
Table 1

Моdified glassy carbon electrodes

Modifiera

Manner

Analyte

Detection limit (М)

Supporting electrolyteb

Sweep modec

Purged

Samplee

Reference

Hg

In situ

Ni (II)

2∙10–6

30 gL−1 H3PO4 + 70 gL−1 Na2SO4 + 10 gL−1 NaCl + Hg (II) (pH 4.5)

LS АSV

Nickel electrodeposits

[44]

Hg

In situ

Pd (II)

9∙10–6

0.2 М KCl (pH 3) + Hg (II) (Hg:Pd ≤ 1:10)

LS АSV

BGD

[45]

Hg

In situ

Fe (II, III), Mn (II)

1∙10–6

0.5 М NaCl + Hg (II) (pH 4.0–6.0 for Mn, pH 3.5–4.0 for Fe)

LS АSV

+

Sea, drinking, service waters

[46]

Hg

In situ

Pb (II), Cd (II)

4.5∙10–12 (Cd); 1∙10–9 (Pb)

0.01 М amm. buff. (pH 5.6) + 5∙10–3 М SCN + 3∙10–5 М Hg (II)

SQW АSV

+

Lake water

[47]

Hg

In situ

Cd (II), Pb (II), Cu (II)

10–9

0.1 М KNO3 + 0.03 М HNO3 + 1∙10–4 М Hg(NO3)2

LS АSV

BGD

[48]

Hg

In situ

Pb (II), Cd (II), Bi (III)

5∙10–4% (Pb); 2∙10–5% (Cd); 7∙10–3% (Bi)

0.35 М KCl + 0.01 М HCl + 5∙10–6 М Hg (II) (pH 2.0)

LS АSV

Soils, cement, rocks

[49]

Hg

In situ

Cu (II), Pb (II), Cd (II)

10–9–10−11

1 М HClO4 + 5∙10–4 М Hg (II)

DP АSV

+

Sea waters

[50]

Hg

In situ

Cu (II), Pb (II), Cd (II)

2∙10–5 (Pb); 7∙10–5 (Cd); 1.6∙10–4 (Cu)

2 М NaCl (0.5 М HCl) + 1∙10–4 М Hg (II)

AC АSV

Surface, waste water

[51]

Hg

In situ

Pb (II), Cd (II), Cu (II), Zn (II)

1∙10–9 (Pb); 1∙10–10 (Cd); 1∙10–8 (Cu); 1∙10–8 (Zn)

1 М LiCl (0.2 М HCl) + 1∙10–4 М Hg(NO3)2

SQW АSV

+

Surface, waste water

[5253]

Hg

In situ

Cu (II), Pb (II), Cd (II), Zn (II)

2∙10–10 (Сu); 1∙10–10 (Pb); 7∙10–11 (Сd); 6∙10–10 (Zn)

0.1 М NaAc + 5∙10–5 М Hg (II) (Cu, Cd, Pb); 0.1 М NaAc + 5∙10–5 М Hg (II) + Ga (III) (Zn)

LS АSV

Extract from river sediment

[54]

Hg

In situ

Cu (II), Pb (II), Cd (II), Zn (II)

6∙10–11(Zn); 2∙10–11 (Cd); 1∙10–11 (Pb); 5∙10–11 (Cu)

0.025 М KCl (рН 3.5) + 0.3 gL–1 Hg (II)

DP АSV

+

Sea waters

[55]

Hg

Ex situ

Cu (II)

2∙10–8

0.1 М HNO3

SQW АSV DP АSV

Waters, pharmaceutical preparations

[56]

Hg

Ex situ

Pb (II)

5∙10–9

2.5 М NaCl + 0.25 М asc. ac. + 0.24 М NaOH

DP АSV

+

Soil, air

[57]

Hg

Ex situ

Tl (I)

1∙10–9

0.13 М EDТА + 0.58 М asc. ac.  +   0.7 М NaOH

DP АSV

+

Soils

[58]

Hg

Ex situ

Tl (I)

5∙10–10

0.17 М EDТА + 2 mМ HCl + 0.03 М asc.ac

LS АSV

+

Natural waters

[59]

Hg

Ex situ

Ba (II), Pb (II)

7∙10–10 (Ba); 5∙10–10 (Pb);

0.1 М HClO4 or 80% ethanol  +   0.1 М TBAP

DP АSV

+

BGD

[60]

Hg

Ex situ

Pb (II), Cu (II)

6∙10–11 (Pb); 2∙10–10 (Cu)

0.01 М NH4Ac–HCl   +   1.2∙10–4 mМ NaSCN (pH 3.4)

DP АSV

Sea water

[61]

Hg

Ex situ

Pb (II), Cu (II), Cd (II)

10–9

0.05 М HCl + 70% methanol (pH 4–6)

DP АSV

+

Foodstuffs

[62]

Hg

Ex situ

Pb (II), Cu (II), Cd (II)

10–7

0.1 M HNO3 + 5–10 gL−1 SDS

DP АSV

+

Fruit juice, wine, beer, milk powder, waste water

[63]

Hg

Ex situ

Zn (II), Cu (II), Pb (II), Cd (II)

5∙10–10–1∙10–9

0.1 М KNO3 + 2 mМ HNO3

SQW АSV

Waste water

[64]

Hg

Ex situ

Zn (II), Cu (II), Pb (II), Cd (II)

4∙10–7 (Zn); 2.7∙10–9 (Cd); 6.8∙10–9 (Pb); 4∙10–8 (Cu)

0.2 М HNO3

SQW АSV

Sweet water

[65]

Hg

Ex situ

Zn (II), Cu (II), Pb (II), Cd (II)

8∙10–9 (Zn); 9.7∙10–9 (Cu); 1.6∙10–8(Pb); 8.6∙10–9 (Cd)

0.01 М LiCl (pH 2.9)

SQW АSV

+

Fuel

[66]

Hg

Ex situ

Сu (II), Pb (II), Cd (II), Zn (II)

1 ng g−1

0.075 М NaNO3

LS АSV

+

Sugar, syrup

[67]

Hg

Ex situ

Cu (II), Pb (II), Cd (II), Zn (II)

10–8 –10–9

0.1 М citric acid   +   1∙10–4 М Fe (III)

LS АSV

BGD, extracts from turf

[68]

Hg/Сu

Ex situ/in situ

Se (IV)

1∙10–9

0.1 М HClO4 + 1 mgL−1 Cu (II) + 0.02 М NaSCN   +   5∙10–3 М EDТА

DP CSV

+

BGD

[69]

Hg, 8HXQ

In situ

Mo (VI)

5∙10–9

0.2 М NaAc (pH 5.25)   +   5∙10–5 М Hg (II) + 10–3 М 8HXQ

DP CSV

+

Biomaterials and background objects

[70]

Hg, DMG

In situ

Ni (II)

1.3∙10–10

0.1 М KNO3 + 2∙10–4 М DMG   +   5∙10–5 М Hg(NO3)2 (pH 9)

SQW CSV

Soils

[71]

Hg/RSH

Ex situ

Cd (II)

4∙10–12

0.01 М NaAc (рН 3.0)

SQW CSV

+

Sea water

[72]

Hg, catechol

In situ

Sn (IV), Pb (II)

5∙10–9 (Pb); 4∙10–9 (Sn)

0.1 М NaAc (рН 4.5) + 5∙10–4 М catechol   +   1 gL−1 Hg (II)

DP CSV

+

Biomaterials, foodstuffs, background objects

[7374]

Hg/ EDA

Ex situ/in situ

Cu (II)

 

0.01 М HCl   +   3∙10–3 М EDA

SQW ASV

Sea water

[75]

Hg/ DMG

Ex situ/in situ

Ni (II)

10–6

0.25 М NH3 + 0.25 М NH4NO3 + 0.25 М NaSCN   +   1∙10–4 М DMG

LS CSV

BGD

[76]

Hg/18C6

Ex situ/in situ

Pb (II)

1∙10–4

0.1 М LiNO3 (or LiClO4) + 2.9∙10–3 М 18C6

SQW ASV

+

BGD

[77]

Hg/ CHD or DMG

Ex situ/in situ

Co (II), Ni (II)

1∙10–9

30 mМ HEPES   +   0.1 М NaClO4 (pH 7.4) + CHD or DMG

DP CSV

+

Model mixtures

[78]

Hg/ CHD or DMG

Ex situ/in situ

Co (II), Ni (II)

5∙10–9 (Ni); 2∙10–9 (Co)

0.1 М HEPES (pH 7.4) + 1∙10–4 М CHD or DMG

SQW CSV

Biological liquids

[79]

Hg/ DMG (1), Hg/ 8HXQ (2)

Ex situ/in situ

Ni (II) (1), Cu (II) (2)

9∙10–10 (Ni), 1∙10–9 (Cu)

0.1 М amm. buff. (pH 9) + 0.001 М DMG (Ni); 0.01 М PIPES (pH 6.8) + 5∙10–5 М 8HXQ (Cu)

SQW CSV

BGD

[80]

Au

Ex situ

As (III)

1.6∙10–8

HCl + Na2SO3

DP ASV

+

Natural waters

[81]

Au nanoparticles

Ex situ

As (III)

1.3∙10–10 (LS ASV); 2∙10–10 (SQW ASW)

1 М HCl

LS ASV SQW ASV

+

River waters

[82]

Au

Ex situ

Au (III)

4∙10–9

0.7 М HCl   +   0.32 М HNO3

DP ASV

SS of gold ore

[83]

Au

Ex situ

CH3Hg+

2∙10–8

0.1М NaNO3 + 0.14 М HNO3

DP ASV

Model solution

[84]

Au

Ex situ

Se (IV), Te (IV)

1.3∙10–10(Se); 1.6∙10–10(Te)

0.1 М HNO3

DP ASV

+

Copper

[85]

Au/PVP

Ex situ

Hg (II)

5∙10–10

0.025 М H2SO4 + 0.05 М KCl

SQW ASV

Natural waters

[86]

Cd

In situ

Hg (II)

4.5∙10–9

0.1 М NH4Br   +   10–8 М Cd (II)

LS ASV

Natural waters

[87]

Cu (1); Au (2); Se (3)

In situ

Se (IV), Au (III)

3.8∙10–5 (Se), 1.5∙10–5 (Au)

0.1 М HClO4   +   16(10) mgL−1 Cu(II) (Au(III)) (Se); 0.1 М HClO4 + 10 mgL−1 Se (IV) (Au)

SQW CSV

Vitamins

[88]

Pb

In situ

Ni (II), Co (II)

1.6∙10–9 (Ni); 1∙10–9 (Co)

0.1 M PIPES + 5∙10–3 M DMG + 2.5∙10–5 M Pb(NO3)2 (pH 6–9)

SQW CSV

SS of water and tea leaves

[89]

Pt nanoparticles

In situ

As (III)

2.8∙10–8

1 M HClO4

LS ASV

+

Drinking water

[90]

Bi

In situ

In (III)

10–8

0.1 М NaAc (рН 4.5) + 0.1 М KBr   +   200 µgL−1 Bi (III)

SQW ASV

Model solutions

[91]

Bi

In situ

Zn (II), Cd (II), Pb (II)

1∙10–9 (Pb); 2∙10–9 (Cd); 1∙10–8 (Zn)

0.1 М NaAc   +   500 µgL−1 Bi (III)

SQW ASV

Tap water, biomaterials

[92]

Bi

Ex situ

Cu (II)

7.8∙10–8

0.1 M acet. buff. (pH 4.75) + 2.5∙10–4 M Ga (III)

SQW ASV

 

Model solution

[93]

Bi

Ex situ

Cd (II), Pb (II)

5∙10–7

0.05 М NaAc

SQW ASV

BGD

[94]

Bi

Ex situ

Zn (II), Cd (II)

4.3∙10–7 (Zn); 5.9∙10–9 (Cd)

0.1 М NaAc

SQW ASV

BGD

[95]

Bi

Ex situ

In (III), Tl (I), Cu (II), Cd (II), Pb (II), Zn (II)

10–7

0.1 М NaAc (рН 4.5)

SQW ASV

BGD

[96]

Bi/ CAA

Ex situ/in situ

V (V)

2∙10–8

0.1 M acet. buff. (pH 5.5) + 50 μM CAA + 4 mM KBrO4

SQW CSV

Groundwater

[97]

Bi/ DMG

Ex situ/in situ

Co (II)

1.8∙10–11

0.0125 М PIPES   +   0.002 М HEPES   +   75 mgL−1 CTAB   +   2.4∙10–4 М DMG (рН 6.5)

DP CSV

+

Tea leaves, natural and drinking waters

[9899]

Bi/ CF

Ex situ/ in situ

Cr (VI)

2∙10–9

0.01 М PIPES   +   0.2 М KCl   +   0.1 mМ CF

SQW CSV

Tap water, soils

[100]

Bi/ТEА

Ex situ/in situ

Fe (III)

7.7∙10–9

0.1 М NaOH   +   0.01 М ТEА   +   5∙10–3 М KBrO3

DP CSV

+

Standard sample of river water

[101]

Bi/ DTPA

Ex situ/in situ

Cr (VI)

3∙10–10

0.1 М NaAc (pH 4.5) + 0.25 М KNO3 + 1∙10–6 М DTPA

SQW CSV

+

River waters

[102]

Bi/ DMG

Ex situ/in situ

Co (II), Ni (II)

1.2∙10–9 (Co); 1.7∙10–9 (Ni)

0.2 М аmm. buff. (pH 9.2) + 1∙10–4 М DMG

SQW ASV

Ore, river water

[103]

Bi/ CAA

Ex situ/in situ

Mo (VI)

2∙10–9

0.05 М аcet. buff. (pH 5.5) + 5∙10–5 М CAA

SQW CSV

Sea water

[104]

Bi/cupferron

Ex situ/in situ

U (VI)

4∙10–10

0.01 M PIPES + 0.05 M KCl + 0.1 mM cupferron

SQW CSV

Sea water

[105]

Pb-Cu/DMG + NO2

In situ

Co (II)

1∙10–11

0.2 М (NH4)2SO4 + NH4OH +  0.5 M NaNO2 + 2∙10–3 М DMG + 5∙10–5 М Cu (II) + 1.5∙10–5 М Pb (II) (pH 8.5)

SQW CSV

SS, water

[106]

8HXQ

In situ

Sn (II)

2∙10–6

0.1 М NaAc (рН 6) + 8HXQ

SQW

+

Tooth paste, pharmaceutical preparations

[107]

HEPES

In situ

U (VI)

1∙10–9

0.02 М HClO4 (pH 4) + 2∙10–5 М HEPES

SQW CSV

+

Food stuffs, fertilizers, cement

[108]

ТМАC

In situ

Al (III), Mg (II)

5∙10–11 (Al); 4∙10–10 (Mg)

0.01 М KNO3 (pH 5.0) + 0.02 М ТМАC

SQW ASV

+

Food stuffs, fertilizers, cement

[109]

DFO

In situ

Al (III)

2∙10–7

0.05 М amm. buff. (рН 8.3–8.9) + (10–4–10–5) М DFO, THMP, DHP

DP ASV

Natural waters, biological liquids

[110]

DDTACD

Ex situ

Au (III)

8.3∙10–8

0.1 М NaCl + 0.01 М NaAc (pH 4)

SQW CSV

Geological samples

[111]

8MQN

Ex situ

Ag (I)

2.7∙10–11

0.1 М NaAc (рН 4.3) (accumulation), 0.1 М HNO3 + 0.05 М KBr (sweep)

LS ASV

Sea waters, rice

[112]

PAN

Ex situ

Сd (II)

5∙10–10

0.1 М NaH2PO4

LS ASV

Model solution

[113]

ARS

In situ

Cu (II)

1∙10–6

0.1 М H3PO4 + 0.1 М ARS

CV

BGD

[114]

Alizarin

Ex situ

Cu (II)

1∙10–4

0.5 М Na2SO4 (pH 4)

CV

BGD

[115]

BPD

In situ

Fe (II)

10–7

0.025 М KCl   +   1 gL−1 BPD

DP АVA

+

Soils

[116]

Dithizone

Ex situ

Hg (II)

5∙10–10

0.1 M KJ (pH 2)

LS ASV

Sea water

[117]

MAA

Ex situ

Hg (II)

4∙10–2

0.1 М HNO3

LS ASV

BGD

[118]

BPD

Ex situ

Pb (II)

1∙10–7

0.1 М NaAc (рН 4.5)

LS ASV

+

Model solutions

[119]

Humic acids

Ex situ

Fe (II), Cu (II), Ni (II)

2.0∙10–6 (Fe); 6.0∙10–7 (Cu); 6.0∙10–6 (Ni)

0.1 М KHPh (Fe, Cu); 0.1 М Na2SO4 (Ni)

SQW ASV

BGD

[120]

PCC

Ex situ

Ce (III)

2.0∙10–10

0.1 М NaOH

DP ASV

+

SS, hair

[121]

KF-222

Ex situ

Hg (II)

10–12

0.01 М NaAc (рН 4) + 0.1 М NaClO4

SQW ASV

Sea and waste waters, saliva

[122123]

CA

Ex situ

Hg (II)

2.5∙10–8

0.1 М H2SO4 + 0.01 М NaCl

SQW ASV

+

Natural waters

[124]

TCA

Ex situ

Cu (II)

2∙10–9

0.1 M B-R (pH 4.5)

DP ASV

+

Natural waters

[125]

TCA

Ex situ

Pb (II), Cd (II)

2∙10–8 (Cd); 8∙10–9 (Pb)

0.1 M acet. buff.

DP ASV

+

Natural waters

[126]

Nafion

Ex situ

Pb (II)

5∙10–9

0.1 М NaCl   +   0.05 М HCl

SQW ASV

Standard sample TMDA-52.2

[127]

Nafion

Ex situ

Sn (IV)

8∙10–10

0.01 М NaCl   +   HCl (pH 1.9)

LS CSV

Hair

[128]

Nafion

Ex situ

CH3Hg+

4.5∙10–8

0.01 М HClO4

SQW АV SQW DDV

+

BGD

[129]

Nafion

Ex situ

Fe (III), Fe (II)

10–9

(0.03–0.3) М HCl

SQW DDV

+

Interstitial waters

[130131]

Nafion /Hg

Ex situ

Cd (II)

1∙10–10

0.01 М NaAc

LS ASV

+

Blood

[132]

Nafion /Hg

Ex situ

Cu (II)

1.6∙10–6

0.1 М HNO3

SQW ASV

+

Beer

[133]

Nafion /Hg

Ex situ

Cu (II)

1.5∙10–8

0.1 М acet. buff. (pH 3.5)

DP ASV

+

Estuarial water

[134]

Nafion /Hg

Ex situ

Pb (II)

2∙10–7

0.1 М TRIS   +   0.6 М NaCl

SQW ASV

+

BGD

[135]

Nafion /Hg

Ex situ

Pb (II)

1∙10–7

0.02 М KNO3 (pH 5)

DP ASV

+

Model solution

[136]

Nafion /Hg

Ex situ/in situ

Pb (II)

1.2∙10–9

0.1 М NaAc (pH 4.6) + 85.7 mМ Hg (II)

SQW ASV

Simulated saliva

[137]

Nafion /Hg

Ex situ/in situ

Cd (II), Pb (II)

2∙10–9 М (Cd); 4∙10–9 М (Pb)

0.1 М KNO3 + 2 mМ HNO3 + 1∙10–4 М Hg (II)

SQW ASV

Waste water

[138]

Nafion /Hg

Ex situ

Pb (II), Cd (II)

3∙10–11 (Pb), 5∙10–11 (Cd)

0.1 М NaAc (pH 4.6)

SQW ASV

BGD

[139140]

Nafion /Hg

Ex situ

Pb (II), Cd (II)

9∙10–9 (Cd), 1∙10–7 (Pb)

0.12 М NaAc (pH 7.7)

SQW ASV

+

Sweet water

[141]

Nafion /Hg

Ex situ

Pb (II), Cu (II)

2∙10–8 (Pb), 6∙10–8 (Cu)

0.1 М KNO3 + 5 mМ HNO3

DP ASV

Service waters

[142]

Nafion /Hg

Ex situ

Cd (II), Pb (II)

4.5∙10–8(Cd); 4.8∙10–8 (Pb)

0.1 М NaAc (рН 4.5) + 9.41∙10–5 M FA

DP ASV SQW ASV

+

Model solutions of fulvic acids

[143]

Nafion /Hg

Ex situ

Cu (II), Pb (II), Cd (II)

1.6∙10–8 (Cu); 4.8∙10–9 (Pb); 8.9∙10–9 (Cd)

0.1 М NaAc (pH 4.5)

DP ASV, LS CSV

+

Food stuffs

[144]

Nafion /Hg –Cu

Ex situ

Pb (II)

4∙10–10

5 mМ HNO3 + 0.1 М KNO3

SQW ASV

+

Natural waters

[145]

Nafion /Bi

Ex situ/in situ

Pb (II), Cd (II)

4.8∙10–8

0.1 М NaAc (рН 4.5) + 400 μgL−1 Bi (III)

SQW ASV

Model solutions of SAS

[146]

Nafion /Bi

Ex situ/in situ or ex situ

Pb (II), Cd (II), Zn (II)

5∙10–10 (Pb); 9∙10–10 (Cd); 6∙10–9 (Zn)

0.1 M acet. buff.

SQW ASV

Tap water, urine, wine

[147]

Nafion + HgCl2

Ex situ

Pb (II), Cu (II)

5.8∙10–9 (Pb); 5∙10–8 (Cu)

0.1 M citric acid   +   0.03 M Na2HPO4 + 0.1 M KCl

LS ASV

Sea water

[148]

Nafion + KF-222 (1); Nafion + terpene (2)

Ex situ

Hg (II) (1), Fe (II) (2)

3.8∙10–9 (Hg); 2.5∙10–7 Fe (II)

0.025 М H2SO4 + 0.1 М NaCl (Hg); 0.1 М sulphate buffer (pH 3) (Fe)

SQW ASV SQW CSV

BGD

[149]

Nafion + Na-DDC (1); Nafion + 18C6 (2)

Ex situ

Pb (II), Cu (II), Сd (II), Hg (II)

1∙10–8 (Hg) (1), 1∙10–9 (Cu, Pb, Cd) (2),

0.1 М KNO3 (pH 2.0) (1); 0.1 М NaAc (2)

DP ASV

+

BGD

[150]

Nafion + tobramycin

Ex situ

Cu (II)

5∙10–10

Acet. buff. (pH 4.6)

DP ASV

Water samples, analytical salts

[151]

Nafion + BPD/Hg

Ex situ

Pb (II)

5∙10–10

0.07 М phosphate buffer (pH 4)

SQW ASV

Drinking water

[152]

Nafion + DAB /Hg

Ex situ

Se (IV)

6∙10–9

0.1 М NaClO4

SQW CSV

Natural waters

[153]

Nafion + 8HXQ /Hg

Ex situ

Te (IV)

1.6∙10–9

0.1 М NaClO4 (pH 2.5) + 0.01 М EDТА

SQW CSV

+

BGD

[154]

Nafion + DMG; BPD/Hg

Ex situ

Pb (II), Cu (II)

6.3∙10–8 (Cu); 1∙10–8 (Pb)

NH3/NH4Cl buffer (pH 9)

SQW ASV

Waters, urine

[155]

Nontronite /nafion /Hg

Ex situ

Cu (II)

10–7

0.01 М KNO3

SQW ASV

+

Natural waters

[156]

Tosflex

Ex situ

Cu (II)

9.4∙10–6

0.5 М NaCl   +   0.1 М NaAc (pH 5)

LS ASV

+

BGD

[157]

Tosflex

Ex situ

Hg (II)

2∙10–11

0.5 М NaCl   +   0.01 М HCl

DP ASV

+

Natural waters

[158159]

Tosflex /Hg

Ex situ

Bi (III)

3∙10–9

0.5 М KCl (pH 1.4)

SQW ASV

+

Waters

[160]

Tosflex /Hg

Ex situ

Tl (III)

5∙10–10

0.5 М KCl (pH 5.6)

SQW ASV

Model solutions

[161]

Tosflex /Hg

Ex situ

Zn (II)

1.5∙10–9

0.02 М H2SO4

SQW ASV

+

Model solutions

[162]

Tosflex + DAB /Hg

Ex situ

Se (IV)

1.3∙10–9

0.1 М KCl

SQW CSV

+

Sea and sweet natural waters

[163]

Tosflex + 8HXQ /Hg

Ex situ

Te (IV)

1.6∙10–9

0.1 М KCl (рН 3)

SQW CSV

+

Model solutions

[164]

PPG

Ex situ

Sb (III)

4.1∙10–10

0.04 М NaAc (рН 5.5) (accumulation); 1.0 М HCl (sweep)

DP ASV

+

Sea water, hair

[165]

PPD

Ex situ

Hg (II)

1∙10–10

0.5 М NaCl   +   0.01 М HCl

DP ASV

+

Interstitial waters

[166]

PP + PDDT

Ex situ

Cu (II)

1∙10–6

0.1 М NaAc

CV

Model solution

[167]

PMR

Ex situ

Hg (II)

4.4∙10–11

B-R buff. (pH 2.56)

LS ASV

Like water

[168]

CA

Ex situ

Pb (II), Cd (II)

2∙10–7

0.1 М NaAc

DP ASV

+

Model solution

[169170]

Nontronite/CA

Ex situ

Cu (II)

2.7∙10–8

amm. buff. (pH 10)

SQW ASV

Natural waters

[171]

OxPPh or Morin hydrate

Ex situ

Sn (II, IV), Sb (III)

5∙10–8 (Sn); 5∙10–8 (Sb)

0.5 М HCl   +   1.5 М NaCl

LS АSV

Natural waters

[172173]

polymer – EDTA

Ex situ

Pb (II), Cu (II), Hg (II)

6∙10–10 (Pb); 2∙10–10 (Cu); 5∙10–10 (Hg)

0.2 М NaAc

SQW ASV

+

Tap water, SS of rine

[174]

PDTT – EDTA

Ex situ

Ni (II), Zn (II), Cd (II), Hg (II), Cu (II), Pb (II), Co (II), Fe (II)

6.0∙10–8 (Ni); 9.0∙10–8 (Zn); 6.6∙10–8 (Cd); 0.3∙10–9 (Hg); 0.1∙10–9 (Cu); 0.4∙10–9 (Pb); 5.0∙10–8 (Co); 8.0∙10–8 (Fe)

0.2 М NaAc (рН 2.1; 2.5; 3.0; 4.1; 4.5; 4.9; 5.3; 5.7 for Ni, Zn, Cd, Hg, Cu, Pb, Co, Fe)

SQW ASV

BGD

[175]

PVP + KF222

Ex situ

Hg (II)

1∙10–9

0.025 М H2SO4 + 0.1 М NaCl

DP ASV

BGD

[176]

PVP /Hg

Ex situ

Pb (II)

1.5∙10–9

0.025 М H2SO4

SQW ASV

Subsoil waters

[177]

PVP /Hg

Ex situ

Tl (III)

5∙10–10

0.01 М HNO3 + 0.1 М KCl

SQW ASV

Subsoil waters

[178]

CА/Hg

Ex situ

Pb (II)

1.9∙10–7

0.1 М NaAc (рН 4.6)

DP ASV

+

Model solutions

[179]

PP /Hg

Ex situ

Cd (II), Pb (II)

1∙10–6

0.1 М NaAc

SQW ASV

+

BGD

[180]

PESA /Hg

Ex situ/in situ

Cd (II), Pb (II)

3.7∙10–9 (Cd); 3.8∙10–9 (Pb)

0.1 М KNO3 + 5 mМ HNO3 + 0.1 mМ Hg (II)

SQW ASV

Model solutions of SAS

[181]

PSSF /Hg; Hg /PLL-PSS

Ex situ

Pb (II), Cd (II), Cu (II)

1.2∙10–10 (Pb); 9∙10–10 (Cu); 6.5∙10–10 (Cd)

0.5 М NaCl

SQW ASV

Natural waters

[182184]

PSSF + chabazite /Hg

Ex situ

Zn (II)

5∙10–7

0.01 М KNO3

SQW ASV

+

Model solutions

[185]

leaven

In situ

Au (III)

6.0∙10–8

0.1 М HCl   +   0.1 М HNO3

LS CSV

+

BGD

[186]

CNT

Ex situ

Hg (II)

2∙10–10

0.1 М HCl   +   0.02 М KJ

DP ASV

Lake water

[187]

CNT

Ex situ

Cd (II), Pb (II)

6∙10–9 (Cd); 4∙10–9 (Pb)

0.1 М NaAc   +   0.02 М KJ

DP ASV

Lake water

[188]

CNT + Nafion

Ex situ

Cd (II)

4∙10–9

Acet. buff. (pH 5)

DP ASV

Water samples

[189

GCM-Au/MWCNT

Ex situ

Tl (I)

2∙10−6

10 mM HNO3   +   10 mM NaCl

LS ASV

BGD

[190]

aCAA Chloranilic acid, 8HXQ 8-hydroxyquinoline, DMG dimethylglyoxime, RSH ω-mercaptocarboxylic acid, EDA ethylenediamine, 18C6 18-crown-6-ether, CHD 1,2-cyclohexanedione dioxime, PVP poly(4-vinylpyridine), CAA chloranilic acid, CF cupferron, ТEА triethanolamine, DTPA diethylene triamine pentaacetic acid, ТМАC tetramethylammonium chloride, DFO diferrioxamine, DDTACD 8,9,17,18-dibenzo-1,7-dioxo-10,13,16-triazacyclooctadecane, 8MQN 8-mercaptoquinoline, PAN polyacrylonitrile, ARS alizarin red S, BPD 2,2′-bipyridyl, PCC pyrocatechol, KF-222 Cryptofix-222, MAA mercaptoacetic acid, CA calix[6]arene, TCA p-tert-butylthiacalix[4]arene, ACA p-allylcalix[4]arene, PES poly(estersulfonate), DDC diethyldithiocarbamate (e.g., Na, Zn), DAB 3,3′-diaminobenzidine, PPG polypyragollol, HEPES N-(2-hydroxyethyl)piperazine-N′-3-propane sulfonic acid, PPD PP derivative, PP polypyrrole, PDDT (pyridyl)-5,6-diphenyl-4,4′-disulfonate-1,2,4-triazine, PMR polymethil-red. CA cellulose acetate, OxPPh oxidized polyphenol, EDTA ethylenediaminetetraacetic acid, PDTT poly-3′,4’′-diamino-2,2′,5′,2″-terthiophen, PESA poly(ester sulfonic) acid, PSSF poly(styrene sulfonate), PLL-PSS poly-l-lysine-poly(sodium 4-styrenesulfonate), CNT carbon nanotubes

b Amm.buff. Ammonium buffer, asc.ac. ascorbic acid, TBAP tetrabutylammonium perchlorate, SDS sodium dodecyl sulfate, PIPES piperazine-N,N′-bis(2-ethane sulfonic acid), CTAB cetyl trimethylammonium bromide, THMP 3-hydroxy-2-methyl-4H-pyran-4-one, DHP 2,3-dihydroxypyridine, KHPh potassium hydrophthalate, acet.buff. acetate buffer, TRIS tris(hydroxymethyl)methylamine, FA fulvic acids, TEA-Br tetraethylammonium bromide, B-R buff. Britton-Robinson buffer

c LS Linear sweep, ASV anodic stripping voltammetry, SQW square wave, DP differential pulse, AC alternating current, CSV cathodic stripping voltammetry, CV cyclic voltammetry, AVA anodic voltammetry, DDV double differential voltammetry, MSWV multiple square wave voltammetry

d + After, without oxygen removal

e BGD Supporting electrolyte, SS standard sample, SAS surface active substances

The GCE modifiers in common use are metals (mercury [4468], gold [8185], cadmium [87], copper [88], lead [89], platinum [90], bismuth [9196]) and facilitating the precipitation of amalgam-forming and electropositive elements. Organic substances (OS) [107121], macrocyclic compounds [122126], polymers [127131, 157159, 165166, 169175], bioactive compounds [186], and nanotubes [187190] can also serve as GCE modifiers. Different combinations of the modifiers—a metal and OS [7080, 97105, 106], a polymer and a metal [86, 132147, 160162, 177184], a polymer and OS [149151, 167, 174176], a polymer, OS, and a metal [152155, 163164, 185]—are used for the GCE surface modification. Water-soluble OS are generally immobilized in situ onto the surface of a pre-activated electrode [7071, 7380, 97110, 114, 116], while low-soluble OS are immobilized ex situ [72, 111113, 115, 117126, 149155, 185]. OS are localized on either the GCE surface [107126] or the first modifying layer of mercury [7080], bismuth [97105] or lead–copper [106].

For a more profound immobilization of the compounds, GCE is pre-polarized at a constant potential of (1.2 ÷ 2.0) V [36, 39, 41] or undergoes multiple (up to 100) polarization cycles between 0 and +1.2 V in 0.1 M NaOH [40]. Some investigators think that, in this case, new functional groups appear on the surface [3941], whereas others are inclined to consider the formation of an oxidized GC film [36]. Still, they are agreed that the anodic polarization radically changes the structure and the composition of the electrode surface, making it possible to fix the modifier or the measured ions on the surface through the ion exchange, the covalent bonding or the electrostatic interaction.

Polymer-coated electrodes constitute a big group of GCE [127183]. Unique properties of the polymer surface and applications of current-conducting polymers are described in Ivaska [192]. To make a polymer film in the form of a “spin coat”, several droplets of the liquid polymer are placed in the working zone, and the electrode is spindled until the polymer film is uniform in thickness. One more method for making of a polymer film (polyaniline, polypyrogallol, polycatechol, etc.) consists in its oxidative electro-polymerization growing from a monomer solution. It was proposed to make superfine (3,000 Å) polymer films on GCE by an original method of “electrostatic spraying” [169, 170], which involves preparation of a “spray liquid” under the action of a strong electric field. For example, to apply a cellulose acetate film, a strong electric field (the voltage of 14 kV) was applied to a dielectric mixture, which was composed of cellulose acetate, acetone, and magnesium perchlorate (a porophore). The liquid was charged and was broken into tiny droplets so that a thin, uniform, and homogeneous film covered the electrode. The polymer electrode films generally have a cross-linked structure and act as molecular sieves separating coarse particles, e.g., protein molecules. Moreover, they can function as ion exchangers. For example, nafion and tosflex (fluocarbon polymers) act as a cation exchanger and an anion exchanger, respectively. Some investigators implanted analytical reagents into the structure of current-conducting polymers [148154, 162163, 178] providing the enhanced selectivity of the polymer film. The high selectivity to metal ions was achieved [174175] because polymers with covalently grafted ethylenediaminetetraacetic acid (EDTA) groups were synthesized on GCE. The response selectivity is efficiently improved by the “guest–host” interaction. Properties of crown ethers acting as host molecules for ions of guest metals were used [77, 112, 108109, 148149, 176] for measurements of Au (III), Hg (II), Cu (II), Pb (II), and Cd (II) ions on electrodes modified by crown-ether adsorption and a nafion film with immobilized macrocycles.

One more method for improvement of the voltammetric selectivity is the use of electrodes with monolayers of organic molecules self-organized on the electrode surface [72, 193194]. For example, ω-carboxylic acids with hydrocarbon chains of different lengths can arrange themselves to the Langmuir palisade on gold or mercury surfaces. While possessing discrimination properties, functionalized layers can change the transport of depolarizer particles to the electrode surface not only due to different charges, but also due to the hydrophobic effect.

The pioneering studies concerned with the use of nanotube-modified GCE include the research performed by a group of Taiwan investigators [187, 188]. Such electrodes provided sufficiently low detection limits for elements. However, the introduction of these electrodes to the analytical practice requires solving the problem of structural ordering in the nanotube layer which influences the reproducibility of measurement results.

A serious problem in the use of GCE is the degradation of the modified surface showing up as the displacement of the current peak potential of the determined element, the distortion of the peak shape, and the emergence of additional peaks [195]. To make the GCE surface reproducible, it is prepared and cleaned by a great variety of methods such as mechanical polishing [108], treatment with reagents [76], electrochemical treatment by polarization at high anode potentials [36, 186], and exposure to microwaves or ultrasound [29, 40, 131]. Mechanical polishing of the surface with abrasive diamond or Al2O3 powders or special polish cloths is in most common use. This surface treatment method is not only laborious and time-consuming, but what is the worst does not guarantee that the surface properties will be reproducible. This problem was attacked by development of automatic devices for cleaning of the solid electrode surface [116], but they have been used on a narrow scale because of their complexity and high cost. The original approach has been used [190] to modify GC with glassy carbon spheres covered by nanoparticles of precious metals and multiwalled nanotubes.

Carbon-paste electrodes

In 1958, Adams described a new type of the carbon-paste electrode (CPE) for voltammetry. This electrode was conceived because despite good performance capabilities of mercury electrodes with respect to the adsorptive concentration of inorganic ions [196198], they have some limitations at positive potential range, while many solid electrodes, which are operable over a wide interval of potentials, cannot selectively sorb the required component of the system. Adams’ idea was not overlooked by other investigators, and in 1964, Kuwana et al. performed research making the first contribution to the advancement of chemically modified carbon-paste electrodes, which are described in the reviews [199201].

CPE is made of a homogenized paste of fine-dyspersated coal and a water-immiscible binding liquid. Paraffin, petrolatum, or polychlorotrifluoroethylene oils, silicon fluid, dioctylphthalate, α-bromnaphthalene, tricresyl phosphate, and other materials can be used as the binding liquid. Two types of CPE pastes are available: dry (0.3–0.5 ml of the binding liquid per 1 g of the carbon powder) and wet (0.5–0.9 ml of the binding liquid per 1 g of the carbon powder) pastes. CPE can bear a high residual current caused by oxygen admixed to the paste with carbon powder particles. The residual current can be eliminated if the preheated carbon powder is mixed with wax, paraffin, or petrolatum oil in the nitrogen atmosphere or a lipophilic paste fluid (tricresyl phosphate) is added. The detection limit (LOD) of many inorganic and organic substances on CPE generally is 1·10−9 M. LOD is frequently decreased by activation of the electrode at high negative or positive potentials. The anode activation of the electrode is most efficient because interfering organic substances can be removed from the surface in this case. Sometimes the electrode is “shaken up” through the cyclic polarization between large negative and positive potentials.

When compared to other carbon-containing electrodes, CPE has a well-developed surface with a high adsorptivity of various substances. This property of CPE is used successfully in voltammetry for the modification and the adsorptive accumulation of substances to be measured. A modifier can be immobilized on CPE by several means including sorption, covalent binding, dissolution of a lipophilic modifier in the paste fluid, and direct mixing with the carbon paste. Direct mixing of a modifier with the paste is used most frequently. This modification procedure is very simple: a modifier is added to the paste in the dry form or diluted in a small amount of an organic solvent making the paste more homogeneous. Other methods of the modifier immobilization are used least often. The depolarizer is concentrated on the modified CPE surface through adsorption, chemical, or electrostatic interaction of the element to be measured and the modifier. CPE is modified by various organic substances such as aromatic oxycarboxylic acids, aromatic amine and diimine compounds, azocompounds, dyes, thiocompounds, triazines, and quinolines. In addition to the main hydrocarbon chain, molecules of these organic compounds include nitrogen, sulfur, and oxygen atoms, aromatic and aliphatic cycles containing unbound π-electrons, which can interact, on one hand, with the electrode surface and, on the other hand, with the analyte ensuring a high surface adsorption and strong binding to the substance to be determined.

Every so often, the analyte is concentrated on modified CPE with the circuit open using extraction, sorption, ion exchange, and formation of ion pairs. The measurement stage can be accomplished in another electrolyte. As the electrolyte is replaced, it is possible to optimize the measurement parameters (pH, the ionic force, and the potential) and eliminate the interference of other components of the test solution. Dependences of the current peak of the element to be determined on the concentration and the accumulation time on CPE are flattened-out curves because all functional groups of the modifier are saturated.

Table 2 gives examples of specific applications of modified CPE for the voltammetric determination of metal ions [202312]. Sometimes CPE is modified by films of metals and their oxides [202213, 215216]. The electrode is modified most frequently by crown compounds [216221], calixarenes [222], cyclodextrins [223225], nonfunctionalized and functionalized silica [226243], clay minerals (vermiculite and montmorillonite) [244253], ion exchangers in the form of artificial resins [254258 258262], natural humic acids and soils [259263], organic [264310], and bioactivecompounds [311312].
Table 2

Моdified carbon paste electrodes

Modifiera

Manner

Analyte

Detection limit (М)

Supporting electrolyte

Sweep modeb

Purge

Sample

Reference

Aunano

Ex situ

As (III)

3–5∙10–9

0.1 М HNO3

SQW ASV

BGD, mineral water

[202203]

Au

Ex situ

As (III, V)

4∙10–8 As (III); 7∙10–9As (V)

1 М HClO4 + 0.2 M HCl   +   5∙10–6 M Au (III)

LS ASV

+

River water

[204]

Auadatoms

In situ

Au (III)

2∙10–6

0.2 М H2SO4

CVА

Model mixtures

[205]

Au

In situ

Hg (II)

2.5∙10–10

0.1 М HNO3 + 0.02 М KCl + 5∙10–6 М Au (III)

DP АSV

Drinking water

[206]

Bi

In situ

Zn (II), Pb (II), Cd (II)

1.5∙10–8 (Pb)

0.1 М NaAc (рH 4.5) + 0.5 mgL−1 Bi (III)

SQW ASV

Model solutions

[207]

Bi

Ex situ

Cd (II), Pb (II)

9∙10–9 (Cd); 4∙10–9 (Pb)

0.2 M acet. buff. (pH 4.25)

SQW ASV or DP ASV

Tap, sea waters

[208209]

Bi2O3 or Bi

Ex situ

Zn (II), Pb (II), Cd (II)

4.4∙10–8 (Cd); 2.4∙10–8 (Pb)

0.1 M NaAc (pH 4.5)

DP ASV

Waters

[210211]

Hg

In situ

Zn (II)

1.3∙10–7

0.1–0.2 М amm. buff. + 2∙10–5 М Hg(NO3)2

DP АSV

+

Drinking water

[212]

Hg

Ex situ

Cu (II), Pb (II), Cd (II)

5∙10–9

Ammonium acetate buff. (pH 4.5)

DP ASV

Fish muscles and water samples

[213]

Wax + Hg oxalate

Ex situ

Cu (II), Pb (II), Cd (II), Zn (II)

3∙10–9 (Cd)

0.1 M KCl or acet. buff. (pH 3.8)

DP ASV or LS АSV

+

Medicinal plants, tablets

[214]

Pt nanoparticles

Ex situ

Cu (II)

3.9∙10–9

0.1 M acet. buff. (pH 5.9)

LS ASV

Urine

[215]

DB18C6 (1), CuO (2)

Еx situ

Pb (II)

2∙10–9 (1); 2.5∙10–9 (2)

0.1 М NaCl   +   10–3 М 18C6 (1); 0.1 М NaCl (2)

DP ASV LS АSV

+

Soil, snow, air, waters

[216]

DB18C6

Еx situ

Cu (II), Pb (II)

9.5∙10–9 (Cu); 2∙10–9 (Pb)

1 М NaAc (pH 5–6)

LS АSV, SQW ASV

+

Waste waters

[217]

Aza-crown compound

Ex situ

Ni (II), Co (II)

4∙10–8 (Ni); 1.2∙10–7 (Co)

0.1 М NaCl (accumulation); 0.1 М KOH (sweep)

DP ASV (Co + Ni); DP CSV (Ni)

BGD

[218]

DB18C6 and its analogs

Ex situ

Au (III), Pt (IV), Pd (II)

8∙10–9 (Au); 3∙10–7 (Pt); 2∙10–8 (Pd)

0.1 М HCl

DP ASV

SS of ore

[219]

B15C5

Ex situ

Cu (II)

8∙10–7

Water-ethanol (40%) solutions

DP ASV

Strong drinks

[220]

Thiacrown compounds

Ex situ

Ag (I)

5∙10–7

NaClO4 (accumulation); 0.1 М NaAc (sweep)

AVA

BGD

[221]

calix[4]arene

Ex situ

Cu (II)

2∙10–8

Acidified sample (accumulation); 0.1 М HCl (sweep)

DP АSV

Tap water

[222]

a-CD & b-CD

Ex situ

Pb (II), Cd (II), Hg (II)

6.3∙10–7 (Pb); 2.0∙10–6 (Cd); 5∙10–8 (Hg)

1 М HClO4

АSV

BGD

[223225]

Zeolite

Ex situ

Cu (II)

1.5∙10–8

0.05 M NaNO3

DP ASV

+

Dried tomayo, bakosel capsule

[226]

Silica

Еx situ

Cu (II)

2∙10–9

0.1 М NH4OH

LS ASV, SQW ASV

Subsoil, sea waters

[227229]

Silica

Еx situ

Hg (II)

2∙10–9

Solution pH 4–7

SQW ASV

Real Samples

[230]

Silicas mоdified with

amides

Ex situ

Сu (II)

3∙10–9

0.1 М HNO3

DP ASV

Tap water

[231]

AMT

Ex situ

Hg (II)

5∙10–10

Sample (pH 2) (accumulation); 0.05 M KNO3 (sweep)

DP ASV

Natural waters

[232]

AMT (1); AMT/DMG (2)

Ex situ/in situ

Cu (II); Ni (II)

3.1∙10–8 (Cu); 2∙10–9 (Ni)

Ethanolic solution (accumulation); 0.1 M NH4Cl + 2.5∙10–3 М DMG (pH 9 for Ni)

DP ASV (1) DP CSV (2)

Ethanol fuel samples

[233234]

thio-groups

Еx situ

Сd (II)

1∙10–7

0.1 М phosphate buffer (рН 4)

DP ASV

+

Natural waters

[235]

 

Ex situ

Hg (II)

(2.5–6.5)∙10–8

HNO3 (pH 3.0) (accumulation); 0.01 М KNO3 (sweep)

DP ASV

BGD, natural water

[236237]

 

ex situ

Pb (II); Hg (II)

2.4∙10–9 (Pb); 1.5∙10–8 (Hg)

0.2 M HNO3

SQW ASV

BGD

[238]

Mercapto-groups

ex situ

Hg (II)

1∙10–6

рН 1(accumulation); 0.1 М HCl + 5% thiourea (sweep)

DP ASV

BGD

[239]

CPA

ex situ

U (VI)

1∙10–7

0.05 М CH3COONa (pH 5) (accumulation); 0.2 М HNO3 (sweep)

DP ASV

BGD

[240]

 

Ex situ

Сd (II); Pb (II); Cu (II)

8.9∙10–8 (Сd); 4.8∙10–8 (Pb); 1.6∙10–7 (Cu)

0.2 М HNO3

SQW ASV

BGD

[241]

Monsil

Ex situ

Hg (II); Ag (I); Pb (II); Cu (II)

4∙10–4 (Cu); 1∙10–3 (Ag, Hg); 5∙10–4 (Pb)

0.1 М NaClO4 + 1.5 М HClO4 (Hg, Ag, Pb); 0.1 М KCl + 1.0 М HCl (Cu)

CVА

+

BGD

[242]

ZrPH

Ex situ

Cd (II)

2∙10–9

0.05 M B-R buff. (pH 3) (accumulation); 0.1 M citrate buff. (pH 3.5) (sweep)

DP ASV

Artificial synthetic samples

[243]

Vermiculite

Еx situ

Cu (II)

5∙10–9

0.04 М B-R buff. (accumulation); 0.1 М NaNO3 + 0.02 М B-R buff. (sweep)

SQW ASV DP ASV

SRM 1643b (SS)

[244245]

Vermiculite

Ex situ

Cu (II); Ag (I)

1.9∙10–5 (Ag); 3.1∙10–6 (Cu)

0.01 М NaClO4

DP ASV

BGD

[246]

Vermiculite

Ex situ

Hg (II); Ag (I)

5.7∙10–8 (Hg); 6.3∙10–8 (Ag)

B-R buff. − pH 7 (Hg). pH 6 (Ag) (accumulation); B-R buff. (pH 5) + 0.05 М NaNO3 (sweep)

SQW ASV

Model solutions

[247]

Montmorillonite

Ex situ

Cu (II)

4∙10–8

NaAc (рН 5.5)

DP ASV

Model solutions

[248]

Montmorillonite

Ex situ

Bi (III)

1∙10–10

0.1 М HCl

DP ASV

Water, nikel metal samples

[249]

Montmorillonite

Ex situ

Hg (II)

1∙10–10

0.1 М tartaric acid

АSV

BGD

[250]

 

Еx situ

Hg (II)

5∙10–8

1 М KCl (pH 2)

DP ASV

Natural water

[251]

 

Ex situ

Fe (III)

3.6∙10–6

0.05 М KCl (pH 3.2)

DP CSV

BGD

[252]

TZT-HDTA-clay

Ex situ

Hg (II)

5∙10–10

Sample (pH 2–5) (accumulation); 0.05 М KNO3 (sweep)

DP ASV

Natural water

[253]

Dowex СGС241

Ex situ

Cu (II)

6.25∙10–5

0.1 М CH3COONa (pH 6.8)

DP CSV

+

Model solutions

[254]

Dowex 50W-8X

Еx situ

Cu (II)

1∙10–7

0.01 М KNO3 (accumulation); 0.1 М HCl (1 М KNO3) (sweep)

DP ASV

Waste waters

[255]

Amberlite IRS 718

Ex situ

Сd (II)

4.4∙10–8

1 mМ amm. buff. (accumulation); 0.1 М HCl (sweep)

LS АSV

River waters

[256]

Dyolite GT-73

Ex situ

Hg (II); CH3Hg+(I)

2.0∙10–8 (Hg); 9.4∙10–9 (CH3Hg+)

0.1 М HCl

CV

River waters

[257]

Ion-exchange resin

Еx situ

Cu (II); Pb (II); Hg (II)

2.4∙10–7 (Cu); 1.1∙10–7 (Pb); 5.0∙10–8 (Hg)

0.1 М KNO3 + 5∙10–3 М CH3COOH

DP ASV

Drinking water

[258]

Humic acids

Ex situ

Pd (II)

9.4∙10–8

0.1 М B-R buff. (pH  2.8) (accumulation); 1.0 М HCl (sweep)

LS АSV

Catalysts, precious metals

[259]

Humic acids

Ex situ

Pb (II); Cu (II); Hg (II)

4.8∙10–9 (Pb); 7.9∙10–9 (Cu); 8.0∙10–9 (Hg)

0.1 М KNO3

DP ASV

+

SRM 2670 (SS), urine

[260]

Humic acids + EDA

Ex situ

Au (III)

5∙10–8

0.35 М HNO3 (accumulation); 0.8 М HCl (sweep)

DP ASV

Ores

[261]

Humic acids/amides

Ex situ

Hg (I; II)

5∙10–8

0.1 М H2SO4 (accumulation); 0.5 М H2SO4 (sweep)

LS АSV

River waters

[262]

Soils

Ex situ

Cu (II)

1.2∙10–5

0.04 М B-R buff. + 0.1 М KNO3

DP ASV

+

Model solutions

[263]

HSF-Na

In situ

Ag (I)

2.5∙10–12

0.02 М NaAc   +   8.3∙10–5 М HSF-Na + 3 mМ EDТА

DP АSV

+

Tap water

[264]

TTCP

In situ

Ag (I)

1∙10–4

0.2 TBAP + 1∙10–3 TTCP

CV

BGD

[265]

BPG

In situ

Bi (III)

5∙10–10

0.3 М HCl + 2.0∙10–5 М BPG

ASV

+

Waters, hair

[266]

ARS

In situ

Cu (II)

1.6∙10–10

0.04 М B-R buff. (pH 4.56) + 3.6∙10–5 М АRS + 1.6∙10–3 М K2S2O8

SD CSV

Natural water, soil

[267]

ARS

In situ

Zr (IV)

1∙10–10

0.1 М acetic acid + 0.08 M KHP (рН 4.8) + 4∙10–6 М АRS

SD CSV

Ore samples

[268]

ARS + CTAB

In situ

Ce (IV)

6∙10–10

0.1 М HAc-NaAc + 0.2 M KHP (рН 5) + 2∙10–6 М АRS + 6∙10–5 М CTAB

SD CSV

Cast iron samples

[269]

CTAB

In situ

Ti (IV); V (V); Mo (VI)

2.0∙10–9 (Ti); 1.4∙10–9 (V); 4.2∙10–10 (Mo)

0.01 М oxalic acid + x mМ CTAB; x = 0.1 (Ti); 0.25 (V); 0.75 (Mo)

DP ASV

+

Rock, fuel, steel

[270271]

CTAB, Septonex

In situ

Os (IV); Pt (IV); Jr (IV)

5∙10–9 (Os); 1∙10–6 (Pt, Jr)

0.1 M acet. buff. + 0.15 M NaCl + 1∙10–5 M CTAB or Septonex (pH 4.5–6)

DP CSV

+

Industrial waste water

[272273]

EDТА

In situ

Fe (III)

2∙10–7

0.01 М KCl + 3∙10–4 М EDТА (pH 3.0)

DP CSV

+

River and tap waters

[274]

DAN

In situ

Se (IV)

1.3∙10–7

0.1 М KCl (рН 2) + 1∙10–4 М DAN (accumulation); 0.1 М HNO3 + 0.1 М KNO3 (sweep)

LS CSV

+

Natural, waste waters

[275]

Thioridazine

In situ

Pd (II)

4.7∙10–9

0.08 М HCl + 75 mgL−1 Thioridazine

DP АSV

+

Drinking water

[276]

Mo-GGPA, Mo-SA

In situ

Ge (III); Si (IV)

0.17∙10–8 (Ge); 0.09∙10–8 (Si)

0.1 М citrate buff. (рН 2.5) + Mo-GGPA (Мо-SA)

DP CSV

Semiconductors, refined waters

[277279]

PEI

In situ

Ag (I); Hg (II); Cu (II); Pb (II); Cd (II)

0.9∙10–6 (Ag); 1.1∙10–6 (Hg, Cu); 8.0∙10–7 (Pb); 8.4∙10–7 (Cd)

0.1 М KCl (0.1 М KNO3) + 2% PEI (pH 3 for Pb, Cd and pH 2 for Cu)

LS АSV

Tap water

[280283]

IDA

Ex situ

Pb (II)

25.4 μg/kg

(pH 6) (accumulation); acet.-ammonium buff. (pH 3) (sweep)

DP ASV

SS of water

[284]

8HXQ

Ex situ

Tl (I)

4.9∙10–9

0.01 М B-R buff. (pH 7.96) (accumulation); 0.2 М аmm. buff. (pH 10) (sweep)

DP ASV

USEPA SS (WP 386)

[285]

2-methyl-8HXQ

Ex situ

Cu (II)

3.3∙10–9

0.05 М KSCN + 0.05 М HNO3 (accumulation); 0.05 М KSCN + B-R buff. (sweep)

DP ASV

+

SS

[286]

2.3- Dicyano-1.4- naphthoquinone

Ex situ

Ag (I)

5∙10–8

0.1 М KNO3

LS CSV

BGD

[287]

N-p-CPCHA

Ex situ

Cd (II)

5.5∙10–9

0.3 М NH4Cl (pH 5)

DP ASV

Mineral and drinking waters

[288]

N-p-CPCHA

Ex situ

Pb (II)

10–8 – 10–9

0.3 М CH3COONa (pH 6)

DP ASV

Drinking water

[289]

N-p-CPCHA

Ex situ

Co (II)

3.3∙10–7

0.2 М CH3COONa (pH 6)

DP ASV

Vitamin B12

[290]

Dithizone

Ex situ

Pb (II)

8∙10–8

Sample pH 12 (accumulation); 0.1 М HCl (sweep)

DP ASV

River water

[291]

Thiоhydrazone

Ex situ

Cu (II)

8∙10–9

0.1 М HCl

CV

River waters

[292]

BBTSC

Ex situ

Hg (II)

4∙10–8

0.01 М KNO3 (accumulation); 0.1 М HCl (sweep)

SQW ASV

River waters

[293]

FTHD

Ex situ

Cd (II)

5∙10–10

B-R buff. (pH 4)

DP ASV

Model solutions

[294]

DPCO

Ex situ

Hg (II)

5∙10–9

0.1 М KSCN (pH 2)

DP ASV

BGD

[295]

PTL derivative

Ex situ

Сu (I)

5∙10–9

0.5 М CH3COONa (pH 6)

DP ASV

СО NBS 1643

[296]

PTL + nafion

Ex situ

Fe (II)

3∙10–8

B-R buff. (pH 4.5)

DP CSV

Waters, SS of alloys

[297]

Diacetyldioxime

Ex situ

Pb (II); Cd (II)

1∙10–8 (Pb); 4∙10–8 (Cd)

0.1 М NaH2PO4

DP ASV

Natural waters

[298]

PAN

Ex situ

Mn (II; VII)

6.9∙10–9 Mn (II)

Phosphate-borate buffer (рН 8.7) (accumulation); аmm. buff. (pH 9.4) (sweep)

DP CSV

+

SS, sea water

[299]

TDPTA

Ex situ

Co (II)

5.0∙10–10

0.1 М NH4Cl (pH 4.95)

DP CSV

+

Drinking water

[300]

Thiourea derivative

Ex situ

Ag (I)

9.3∙10–8

1 М NaClO4 (pH 3.0)

LS АSV

BGD

[301]

Chelate P

Ex situ

Cu (II)

3∙10–8

Sample (accumulation); 1.0 М HNO3 (sweep)

DP ASV

River water

[302]

Cupron

Ex situ

Cu (II)

4.7∙10–9

amm. buff (pH 8.5) (accumulation); 1.0 М HNO3 (sweep)

LS АSV

Anodic mud, polluted water

[303]

Glyoxal derivative

Ex situ

Hg (II); Ag (I)

1∙10–9 (Hg); 1∙10–10 (Ag)

0.1 М NaAc (pH 5) (accumulation); 0.1 М KNO3 (sweep)

DP ASV

+

SRM 2670 (SS)

[304]

Phenylfluorone

Ex situ

Sb (III)

8.2∙10–9

0.5 М HCl

DP ASV

+

Hair, soil

[305]

PPDA

Ex situ

Pb (II)

1∙10–9

0.1 М KNO3 (accumulation); 0.1 М HCl (sweep)

DP ASV

Sea waters

[306]

Zn-DDC

Еx situ

Hg (II)

8∙10–10

0.1 М HClO4 (accumulation); 0.1 М KSCN + 0.01 М HClO4 (sweep)

DP ASV

+

USEPA SS (WP 386), urine

[307]

DMG + glycerol

Ex situ

Hg (II); Ni (II); Co (II); Pd (II)

10–8

Buffer (рН 4.8)

CSV

 

Rice, tea, hair

[308]

TBP

Ex situ

Zn (II); Ga (III)

2∙10–6

7 М HCl (accumulation); 0.5 М ethanolamine + 0.2 М ТEA-Br (sweep)

CVА

Model mixtures

[309]

Моrin

Ex situ

Zr (IV)

1∙10–8

2.2 М HCl

SD АSV

Ore

[310]

Lichen

Ex situ

Pb (II); Cu (II)

2∙10–5 (Pb)

0.02 М phosphate buffer (Pb); 0.02 М NaAc (Сu)

DP ASV

+

[311]

Lichen

Ex situ

Pb (II)

1∙10–8

NaAc with ionic force 0.01 (accumulation); NaAc with ionic force 0.7 (sweep)

DP ASV

Natural and drinking waters

[312]

For other abbreviations see Table 1.

a HSF-Na Sodium heptyl sulfonate, TTCP 2.5.8-trithio[9]-m-cyclophane, BPG brompyrogallol, DAN diaminonaphthalene, Mo-GGPA molybdenum-germanium heteropolyacid, Mo-SA molybdosilicic acid, PEI polyethyleneimine, IDA iminodiacetate, DB18C6 dibenzo-18-crown-6, B15C5 benzo-15-crown-5, α-CD and β-CD α- and β-cyclodextrins, CPA carbamoyl phosphonic acid, AMT 2-aminothiazole, ZrPH zirconium phosphate, KHP potassium biphthalate, TZT-HDTA-clay 2-thiazoline-2-thiol-hexadecyltrimethylammonium-clay, N-p-CPCHA chlorophenyl cinnamohydroxamic acid, BBTSC benzylbisthiosemicarbazone, FTHD 1-furoylthioureas, DPCO diphenylcarbazone, PTL 1,10-phenanthroline, TDPTA 2.4.6-tri(3.5-dimethylpyrazodyl)-1.3.5-triazine, PPDA poly-n-phenylenediamine, TBP tri-n-butylphosphate

b CVA Cathodic voltammetry, SD second derivative of voltammogram

Electrodes based on silica with self-organizing monolayers, for example, mesoporous silica modified by acetamide of the phosphonic acid provide accumulation and measurement of Cu, Pb, Cd, and U [240241]. CPE modified by biocatalysts, which are constituents of α- and β-cyclodextrins [223225] or natural lichens [311312] are used for measurement of ions of heavy metals.

Solid depolarizers can be studied after their direct infusion to CPE, which has been called the carbon-paste electroactive electrode (CPEE). The CPEE methodology was recognized to be also suitable for insoluble electroactive compounds. The first studies of metals, metal oxides, chalcogenides, salts, and other compounds by CPEE methodology were reviewed by Brainina et al. [313]. Electrochemical transformations taking place on CPEE provide information about the electrochemical activity of solid compounds, their stoichiometry, the oxidized state of elements, the morphology (the size and the shape of particles, crystal defects), the catalytic activity, etc. The CPEE methodology significantly increased the scope of electrochemistry to poorly conducting and insoluble solids. CPEE is used to analyze lead sulfides, magnetite, oxides of silver, tin, copper, and iron, bromides of rare-earth elements, nickel-containing compounds and other solids, e.g., ceramics and classes [314318]. A comprehensive review [319] is dedicated to the electrochemical analysis of solids.

Conclusion

Considering the above numerous examples of the electrochemical study and determination of various elements and compounds, it can be concluded that the modification of the surface of solid electrodes by a variety of methods and substances considerably extends the capabilities of voltammetry and ensures a highly sensitive and selective determination of a wide range of elements traces.

Acknowledgements

Financial support of Russian Foundation for Basic Research (project No. 07-03-96070-r_ural_a) and International Science and Technology Center (projects nos. 342, 2132 and 2897) is gratefully acknowledged.

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This article is distributed under the terms of the Creative Commons Attribution Noncommercial License which permits any noncommercial use, distribution, and reproduction in any medium, provided the original author(s) and source are credited.

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© The Author(s) 2007