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ELECTROREDUCTION AT SOLID ELECTRODE MATERIALS AND VOLTAMMETRIC DETERMINATION OF POTASSIUM HYDROGENPEROXOMONOSULFATE

ELECTROREDUCTION AT SOLID ELECTRODE MATERIALS AND VOLTAMMETRIC DETERMINATION OF POTASSIUM HYDROGENPEROXOMONOSULFATE
Елена Мозговая, аспирант

Николай Блажеевский, доктор химических наук, профессор

Харьковский национальный фармацевтический университет, Украина

Участник первенства: Национальное первенство по научной аналитике - "Украина";

Открытое Европейско-Азиатское первенство по научной аналитике;

UDC 541.138: 54.061/.062: 543.253: 54-39: 541.459

The electrochemical behaviour of potassium hydrogenperoxomonosulfate (KHSO5) at carbositall and Au, Ag electrodes using square-wave voltammetry (SWV)with 0.2 mol L–1 KHSO4 background solution (pH ~ 0.8) (Ep = 0.25 Vvs Ag,AgCl/KСl(sat)) and differential pulse voltammetry (DPV) with 0.01 mol L–1 Na2SO4+8´10–3 Н2SO4 background solution (pH = 0.9) (Ep = 0.14 V vs Ag,AgCl/KСl(sat))correspondingly were studied. The voltammetric methods were developed and the possibility was shown for determination of peroxomonosulfate in model solutionson the studied electrodes.

Keywords: potassium hydrogenperoxomonosulfate; voltammetry; carbositall electrode, Ag electrode, Au electrode

 

Electrochemical analysis is a powerful analytical technique that is utility in pharmaceutical industry and environmental applications. Electroanalysis of high advantages due to high sensitivity, reduction in solvent and sample consumption, high-speed analysis, low operating cost and high scan rate in all cases.

An overview of the development in electroanalytical chemistry demonstrates that solid electrodes represent the most rapidly growing class of electrodes. When surveying the current state of electroanalytical research and the applications of electroanalysis, one concludes that solid electrodes in general are widely used and are practical electrode materials. Electrochemistry involves in its broad sense a chemical phenomena associated with charge separation at an electrode surface. As voltammetric methods continue to develop, the range of working electrode materials continues to expand, and the analyst must remain aware of what is available. Both the geometry and composition of the working electrode material must be considered since they will influence the performance of the voltammetric method. Also, the physical form of the working electrode may influence the diffusion process, while the working electrode material will influence the chemical steps and the electron transfer process involved in the detection of the analyte.

A great variety of solid electrodes have been employed in different voltammetric techniques over the years. Of the many different solid materials that can be used as working electrodes, the most commons are carbon, platinum, and gold [1-9].

Potassium hydrogenperoxomonosulfate (KHSO5) is one of the most widely used disinfectants in a medical practice, among well-known classes of chemical disinfectants – oxidants. It is included in the new generation of modern disinfection agents in the form of a stable triple potassium salt 2KHSO5·KHSO4·K2SO4, such as "Perform"and modified analogue of "Virkon"– "Ecocid S"(KRKA, Slovenia, Novo mesto).

The wide use of KHSO5 demands a reliable analytical tool for its monitoring. Literature dataprovide the following methods for KHSO5 determination.

The procedure of polarographic determination of sulfuric acid peroxide derivatives such as peroxomonosulfate (Caro's acid) and peroxodisulfate (Marshal acid or persulfate) at dropping mercury electrode (DME) was described [10]. However, strong oxidant reduction such as persulfate in the background solution of 0.03 mol L-1 sulfuric acid at DME observed at extremely positive potential area vs. saturated calomel electrode (SCE), where the anodic dissolution of electrode material was occurred (+0.3 V). In the potential range of +0.3 to +0.15 V (vs. SCE) the diffusion current value maintained constant, and at 0.25 V was proportional to the concentration of potassium persulfate. If theperoxomonosulfate is presentin solution in the form of hydrogenperoxomonosulfate two waves overlap, so it can be defined only their total content by polarography at DME [11]. In addition to the low selectivity the proposed method is not sensitive, lower limit of detection was limited as absolute value and residual current fluctuations.

The hydrogenperoxomonosulfate was determined by voltammetry in the background of 1 mol L–1 perchloric acid solution using a smooth platinum rotated electrode as working electrode at +0.214 V (vs SCE) after removal of oxygen during 15 minutes. Only platinum oxide dissolution peak was observed on the background voltammogram at +0.84 V. Platinized platinum electrode through a relatively low resistance to oxidation by atmospheric oxygen, which leads to the formation on its surface of an oxide of platinum, requires advance preparation in order to obtain reproducible potentials, namely holding at +1.4 V for a few minutes to achieve the desired passivation of the electrode surface [12]. This method is not sufficiently sensitive, it allowed to determine hydrogenperoxomonosulfate, starting from a concentration of 5´10–5 mol L–1.

The determination of potassium monoperoxosulfate persisting in some disinfectants in the form of triple salt (2KHSO5∙KHSO4∙K2SO4) based on titration by tin(II)chloride solution in the presence of potassium bromide at 70 °С with potentiometric registration by means of point platinum and glass pH electrodeswas presented. The analysis of «Virkon» solution wasperformed [13].The disadvantages of this technique are the necessity of heating the solution of the test sample to a temperature of 70 °C, and the instability of the titrant solution.

To choice electrode material, which would have had selectivity measurements in specific circumstances, it is necessary to know the mechanism of the electrode process, the degree of filling of the surface agents, there are changed when the electrode material is changed. Also, notice that the behavior of the electrode is not determined by the properties of the metal, thin oxide films on it surface, which strongly differ in electrical characteristics of metals. Total property of precious metals is a good formation of conductive oxide films at anodic potentials.

Allowing for the disadvantages of existing methods, it became necessary to find other electrode materials, and therefore it is perspective to study the behavior of KHSO5 on silver (Ag) and gold (Au) metal and carbositall electrodes because the data is not available in the literature.

In the present work the electrochemical behavior of KHSO5 was examined at metal (i.e., Au, Ag) and carbositall electrodes using square waveand differential pulse rotating disk electrode voltammetry was studied. The results of the procedure development of KHSO5 quantitative determination using the method of calibration graph were shown.

EXPERIMENTAL SECTION

Materials and reagents

The solution of KHSO5 («Oxone®», ACROS ORGANICS) was freshly prepared and standardized iodometrically. Stock solution was prepared by dissolving 0.1537 g of powder (triple potassium salt, 2KHSO5·KHSO4·K2SO4) in 50 mL volumetric flask by double-distilled water to give a concentration of 9´10–2 mol L–1. 10 mL of 9´10–2 mol L–1 solution of KHSO5 was diluted in 100 mL volumetric flask with double-distilled water to obtain a 9´10–3 mol L–1 solution of KHSO5. The stock solution was diluted with the appropriate buffer solution before use. Background solutionfor carbositall electrode was prepared by dissolving of potassium hydrogensulfate (KHSO4) in volumetric flask by double-distilled water. The background solutionfor metal electrodes consists of mixture of sulfuric acid(H2SO4) and sodium sulfate (Na2SO4) solutions.

Electrochemical measurements at carbositall electrode were carried out in the analyzer АVS-1.1 (Volta, St. Petersburg) with a three-electrode scheme by alternating current mode with square wave modulation in potential range +1.0…–1.2 V, W = 1000 rpm, amplitude 40 mV, ν = 65 Hz. The values of potential peaks directly at a maximum are measured by electrochemical sensor "Module EM-04" with an accuracy of ±5 mV. Carbositall electrode was used as a working and an auxiliary electrode, and Ag,AgCl/KСl(sat) electrode type EVL-1М4 as a reference electrode.

Electrochemical measurements at Ag and Au electrodes were carried out in the Voltammetric measuring stand with built-in potentiostat 797 VA Computrace (Metrohm, Switzerland) with a three-electrode scheme by differential pulse mode. For differential pulse voltammetry (DPV) operating conditions were as follows: pulse amplitude, 0.050 V; pulse width, 0.040 s; and scan rate, 0.010 V/s. Rotating disk electrodes (RDE) with exchangeable electrode tips made from Ag or Au were used as a working electrode. Platinum auxiliary electrode with plastic shaft was used as an auxiliary electrode, and Ag,AgCl/KСl(sat) electrode as a reference electrode.

The pH was measured using ionmeter type І-160М (Belarus) with a glass electrode type ESL-43-07 paired with Ag, AgCl/KСl (sat) electrode.All measurements were realized at room temperature.

Scheme of the reduction process is: 

Activation of the electrode

An important factor in using solid electrodes is the dependence of the response on surface state of the electrode. Accordingly, the use of such electrodes requires precise electrode pretreatment and polishing to obtain reproducible results.

Metallic electrodes were pretreated electrochemically or chemically. The carbositall electrode was polished manually with aqueous slurry of alumina powder on a damp smooth polishing cloth (BAS velvet polishing pad), before measurement.

RESULTS AND DISCUSSION

Fig. 1 displays the differential pulse voltammetric responses of 2X10–5 mol L–1 KHSO5 at Ag and Au electrodes in N2-saturated 0.01 mol L–1 Na2SO4+8X10–3 Н2SO4 background solution (pH = 0.9) (reference electrode Ag,AgCl/KСl(sat)); Ep = 0.14 V. Voltammetric behavior of KHSOat carbositall electrode was shown in [14]. The study was conducted in solutions with a concentration of KHSO5 from 0.9X10–5 to 5.4X10–5 mol L–1. Background solution was KHSO4(c = 0.2 mol L–1, pH ~0.8).

Procedure of obtaining results for the calibration graph

a) Ag and Au electrodes

Solutions of chosen supporting electrolytes wereplaced into the electrolytic cell at room temperature, and oxygen was removed by passage of nitrogen through the solution for 2 min. A stock solution of the electroactive compound was added to a final concentration. Nitrogen was introduced for another 1 min and the current-voltage curve recorded. In the supporting electrolytes used, the current-voltage curves remained unchanged for at least 72 h.

b) Carbositall electrode

Working solutions were prepared by diluting different volumes of stock solution and background solution each in 50 mL volumetric flask by double distilled water. 25 mL of the working solution of pure substance was transferred to the cell.

The voltammograms were recorded by scanning the potential toward the negative direction in the potential range from +1.0 V to –1.2V. The graph was plotted in the coordinates: the height of peaks Ip in μA on the ordinate axis and corresponding concentration of KHSO5 c in mol L–1 on the abscissa axis.

The calibration curves obtained based on the limiting currents for the reduction of KHSO5 at carbositall (Fig. 2) electrode (Ep = 0.25 V vs Ag,AgCl/KСl(sat)) and at Ag (Fig. 3.1) and Au (Fig. 3.2) electrodes (Ep = 0.14 V vs. Ag,AgCl/KСl(sat)).

Fig. 1. Voltammogram of the KHSO5 reduction obtained at Ag (dotted) and Au(straight) electrodes in N2-saturated 0.01 mol L–1 Na2SO4+8X10–3 Н2SO4 background solution (pH = 0.9) (reference electrode Ag,AgCl/KСl(sat)); Ep = 0.14 V

Fig. 2. The calibration plot of the KHSO5 reduction current peak vs. concentration with 0.2 mol L–1 KHSO4 background solution (pH ~ 0.8) at carbositall electrode (reference electrode Ag,AgCl/KСl(sat)); Ep = 0.25 V

 

                                                                     1                                                                         2

Fig. 3. The calibration plot of the KHSO5 reduction current peak vs. concentration with 0.01 mol L–1 Na2SO4+8´10–3 Н2SO4 background solution (pH = 0.9) at Ag (1) and Au (2) electrodes (reference electrode Ag,AgCl/KСl(sat)); Ep = 0.14 V

Analytical characteristics of the calibration graphs of KHSO5 voltammetric determination procedure was shown in Tab. 1.

Table 1.

Regression characteristics of KHSO5 voltammetric determination procedure in pure substance

Parameters

Data

Carbositall

Ag

Au

Сoncentration ranges (mol L–1)

(0.9-5.4)X10–5

(0.5-11.0)X10–5

(0.5-9.1)X10–5

Regression equation

I= (8.3±0.6)X103Xс

I= (10.2±1.1)X103Xс+
+(0.09±0.07)

I= (11.8±0.9)X103Xс

Slope (a)

8.3X103

10.2X103

11.8X103

Intercept (b)

0.006

0.09

0.009

a

0.6X103

1.1X103

0.9X103

b

0.05

0.02

0.04

Sa

0.6X103

0.4X103

0.3X103

Sb

0.02

0.07

0.013

Correlation coefficient (r)

0.999

0.997

0.999

LOD (mol L–1)

2.76X10–6

7.26X10–6

2.48X10–6

LOQ (mol L–1)

9.19X106

2.42X10–5

8.26X10–6

METHOD VALIDATION

Precision and Accuracy

Precision is the degree of repeatability of an analytical method under normal operational conditions. The precision and accuracy were determined with standard quality control samples (in addition to calibration standards) prepared in triplicates at different concentration levels covering the entire linearity range. The precision of the assay was determined by repeatability (intraday) and intermediate precision (interday) and reported as RSD % for a statistically significant number of replicate measurements. The intermediate precision was studied by comparing the assays on three different days and the results are documented as standard deviation and RSD %. Accuracy is the percent of analyte recovered by assay from a known added amount. Data from nine determinations over three concentration levels covering the specified range were obtained. The repeatability of the method was determined by assaying five sample solutions of the highest test concentration. The obtained results are summarized in Tab. 2.

LOD and LOQ

In this study, LOD and LOQ were based on the standard deviation of response and the slope of the corresponding curve using following equations.

LOD = 3 Sb/а;           LOQ = 10 Sb/а,

where Sb, the noise estimate, is the standard deviation of the absorbance of the sample, а is the slope of the related calibration graphs. The limit of quantification (LOQ) is defined as the lowest concentration of the standard curve that can be measured with acceptable accuracy, precision and variability (Tab. 1).

Table 2.

Evaluation of accuracy and precision of KHSO5 voltammetric determination procedure (n = 5; P = 0.95%)

Electrode material

Taken (mol L–1)

Found (mol L–1)

Recovery (%±SD)

RSD, %

ε (%)

δ*(%)

Carbositall

3.6X10–5

(3.59±0.12)X10–5

99.7±3.3

2.68

3.3

–0.27

4.5X10–5

(4.52±0.14)X10–5

100.4±3.2

2.55

3.2

+0.44

5.4X10–5

(5.41±0.16)X10–5

100.2±3.0

2.39

3.0

+0.19

Ag

0.99X10–5

(0.98±0.83)´10–5

100.9±8.4

6.71

8.3

+0.01

2.00X10–5

(2.04±0.15)X10–5

101.8±7.5

5.95

7.4

+0.02

11.0X10–5

(11.5±0.68)X10–5

104.2±6.2

4.75

5.9

+0.04

Au

0.99´10–5

(1.10±0.86)X10–5

111.5±8.7

6.26

7.8

+0.12

2.00X10–5

(2.02±0.83)X10–5

101.1±4.1

3.29

4.0

+0.01

9.10X10–5

(9.19±0.32)X10–5

101.0±3.5

2.88

3.5

+0.01

 

* relative to the average reference method of iodometric titration [15].

CONCLUSIONS

Thus, this report demonstrated that the most perspectiveof the studied electrodes are carbositall and gold electrodes.A linear relationship between peak current and concentration was obtained in the range (0.9-5.4)X10–5 mol L–1 and (0.5-9.1)X10–5 mol L–1 (r=0.999) of the KHSO5 concentrations at pH ~0.8. RSD were 2.68 %, 2.55 % and 2.39 % for the 3.6X10–5, 4.5X10–5 and 5.4X10–5 mol L–1 concentrations of KHSO5 model solutions, respectively (δ = –0.27…+0.44 %); LOD = 2.76X10–6 mol L–1, LOQ = 9.19X10–6 mol L–1. While on Au and Ag electrodes these data were as follows. RSD were 6.26 %, 3.29 % and 2.88 % for the 0.99X10–5, 2.0X10–5 and 9.10X10–5 mol L–1 concentrations of KHSO5 model solutions, respectively (δ = +0.12…+0.01 %); LOD = 2.48X10–6 mol L–1, LOQ = 8.26X10–6 mol L–1 on Au electrode. These are the lowestvalues.Onthe Ag electrode these data were as follows. For the concentrations of KHSO5 model solutions 0.99X10–5, 2.0X10–5 and 11.0X10–5 mol L–1 RSD were 6.71 %, 5.5 % and 4.75 %, respectively (δ = +0.01…+0.04 %); LOD = 7.26X10–6mol L–1, LOQ = 2.42X10–5mol L–1 on Ag electrode. SoKHSO5 determinationismore sensitive at carbositall and Au electrodes.

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  • 5.   Roy P.R., Okajima T., Ohsaka T. // Bioelectrochem. – 2003. – Vol. 59. – P. 11.
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  • 7.   Ozkan S.A., Uslu B., Enein H.Y. // Crit. Rev. Anal Chem. – 2003. – Vol. 33. – P. 155-181,
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  • 9.   Uslu B., Ozkan S.A. // Anal. let. – 2003. – Vol. 40. – P. 817-853.
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Ваша оценка: Нет Средняя: 6 (3 голоса)
Комментарии: 4

Сметанина Екатерина Ивановна

Уважаемые авторы! Я не химик, я технолог в корне, поэтому сложно судить о качестве публикации, но, поверьте мне, технологу было интересно вдохнуть истоки химии, поучительно.

Мозговая Елена Александровна

Уважаемая Екатерина Ивановна! Спасибо Вам огромное за Ваш комментарий. С уважением, Елена Мозговая.

Григоренко Любовь Викторовна

Dear authors Helen and Nikolay Blazheevskyi! Your experience is well based and scientifically proved I support thoughts there is numerous pros and cons in these field of studies. So, I have some questions for your theoretical background. Why do you use majority of classic sources of literature, I.e. based from 1946, 1951, 1968, 1993. What change since these epoch in the determination of potassium hydrogenperoxomonosulfate, or maybe you'll be the first investigators in your research. Well, my congratulations and best regards in your carriers success from Hryhorenko luibov

Мозговая Елена Александровна

Вельмишановна Любов Вікторівна! Дякуємо за уважне прочитання нашої роботи. Ми дійсно послалися на класичні роботи Кольтгофа та Распі, які були першими та єдиними у доступній нам літературі стосовно вивчення поведінки гідрогенпероксомоносульфуту. І тому ми запатентували нову методику. Дякуємо за увагу.
Комментарии: 4

Сметанина Екатерина Ивановна

Уважаемые авторы! Я не химик, я технолог в корне, поэтому сложно судить о качестве публикации, но, поверьте мне, технологу было интересно вдохнуть истоки химии, поучительно.

Мозговая Елена Александровна

Уважаемая Екатерина Ивановна! Спасибо Вам огромное за Ваш комментарий. С уважением, Елена Мозговая.

Григоренко Любовь Викторовна

Dear authors Helen and Nikolay Blazheevskyi! Your experience is well based and scientifically proved I support thoughts there is numerous pros and cons in these field of studies. So, I have some questions for your theoretical background. Why do you use majority of classic sources of literature, I.e. based from 1946, 1951, 1968, 1993. What change since these epoch in the determination of potassium hydrogenperoxomonosulfate, or maybe you'll be the first investigators in your research. Well, my congratulations and best regards in your carriers success from Hryhorenko luibov

Мозговая Елена Александровна

Вельмишановна Любов Вікторівна! Дякуємо за уважне прочитання нашої роботи. Ми дійсно послалися на класичні роботи Кольтгофа та Распі, які були першими та єдиними у доступній нам літературі стосовно вивчення поведінки гідрогенпероксомоносульфуту. І тому ми запатентували нову методику. Дякуємо за увагу.
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