RU2381501C2 - Method for quantitative determination of anavidine using stripping voltammetry method - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to analytical chemistry which studies the possibility of determining anavidine through stripping voltammetry. The given task is solved by that the method for quantitative determination of polyhexamethylene guanidine (PHMG) (anavidine) involves transferring anavidine from a sample into a solution through extraction, and voltammetric determination using a mercury film electrode as an indicator electrode. Accumulation is used during 60-90 s with potential of the electrolysis cell at - (0.15-0.3) V relative a 1 M silver chloride electrode on a 0.01 M sodium hydroxide background with subsequent registration of cathode peaks at potential scanning velocity of (80-100) mV/s. Concentration of anavidine is determined from the peak height in the range of potential from -0.8 to -0.95 V by adding standard mixtures. The detection limit equals 0.83·10^-3 mg/l. The proposed method can be used in pharmacokinetics and pharmaceutical researches, in toxicology and technical analysis of guanidine compounds, for monitoring sewage water and air zones of water treatment plants, as well as for designing a method of analysing anavidine and related compounds in complex multi-component biosystems (blood, urine, plasma etc) and food products.

EFFECT: possibility of determining anavidine through stripping voltammetry.

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Description

The invention relates to the field of analytical chemistry, studying the possibility of determining anavidin by inversion voltammetry. Anavidin refers to cationic polymer compounds and is a polyhexamethylene guanidine phosphate (PHMG) with the general formula:

Anavidin is a derivative of guanidine, which ensures its high bactericidal and fungicidal properties. Possessing high antiseptic characteristics, anavidin is widely used in surgery as antimicrobial tissues and dressings, for disinfecting air, disinfecting water, as well as for giving antimicrobial properties to the clothes of medical personnel and patients. In this regard, the determination of the microquantities of anavidin is important for monitoring the pharmacokinetic effect of the drug, evaluating its toxicity and monitoring the quality of water and air in the working area.

This in turn increases the requirements for modern methods for the quantitative determination of polymer guanidine compounds. These methods should have high sensitivity, sufficient selectivity, low time spent on the analysis of the availability of the reagents used, in order to ensure widespread use of these methods in laboratories.

Such options of electrochemical methods as voltammetric (VA) meet modern requirements for quality control of pharmaceuticals, food products, and agricultural products.

The use of inversion in voltammetric methods allows to achieve a minimum detectable concentration of a substance at the level of 10 ^-10 ÷ 10 ^-11 mol / l or 10 ^-4 ÷ 10 ^-5 g / l.

The possibilities of using serial computerized voltammetric analyzers, characterized by high expressivity, selectivity and the possibility of multi-element analysis, often without preliminary sample preparation, allow the use of VA methods for serial analysis in many production laboratories as control methods. Information on the use of electrochemical methods, in particular voltammetric, for the determination of anavidin is missing.

The use of electrochemical methods of quantitative chemical analysis for the direct determination of anavidin is not noted in the literature. However, anavidin as a representative of the guanidine group has sufficient electrochemical activity.

At pH 9 ÷ 9.5 in a solution of 30% ammonium sulfate (catalit) and 20% sulfuric acid (analyte) when a current of 300 A is applied at a temperature of (18-21) ° C in 2 electrochemical cells, where amalgamated copper was used as a cathode, reduction of nitroguanidine to aminoguanidine (1) [T. Duraiswamy Balakrishnan, K. Shrivara Udupa, G. Srinivasan Subramanian, and H. Venkatakrishna Udupa Electrolytic Production of Aminoguanidine Bicarbonate. / Ind. Eng. Chem. Process des. Develop., Vol. 10, No.4, 1971, 495-497].

There are data in the literature on indirect determination of guanidine by voltammetric methods [Dengbai Luo, Jingui Lan, Chun Zhou, and Chenxia Luo Polarographic Behavior of Co (II) -BSA or -HSA Complex in the Presence of a Guanidine Modifier./ Anal. Chem. 2003, 75, 6346-6350]. Against the background of 0.2 M NaOH at a potential of -1.73 V relative to the calomel electrode, the adsorption peak of the complex of cobalt (2+) and guanidine chloride was recorded. In this experiment, a mercury-dropping electrode was used as an indicator electrode. The content of guanidine chloride was 0.1-0.2 mol / L. Under the proposed conditions, guanidine serves as a complexing agent.

As a prototype, the method of capillary electrophoresis was chosen to determine polyhexamethylene guanidine [Rudnev A.V., Dzheryan T.G. Determination of polyhexamethylene guanidine by capillary electrophoresis // Journal of Analytical Chemistry, 2006, T. 61, No. 10, pp. 1086-1089]. Using a quartz capillary with an external polyimide protective coating at an operating wavelength of the ultraviolet spectrum of 200 nm, at an operating voltage of 20 kV, which corresponds to a current of 20 ÷ 50 μA, electrophoregrams of polyhexamethylene guanidine hydrochloride and its oligomers were obtained. The detection limit of polyhexamethylene guanidine in the proposed method is up to 2 · 10 ^-3 g / l.

Under these conditions, the determination of anavidin at a level of n · 10 ^-4 g / l is impossible.

The task of the invention is to establish operating conditions for voltammetric determination of anavidin, as well as increasing the sensitivity and expressness of the analysis.

To determine anavidin, a mercury-film electrode was used. The use of this type of electrodes in the electrochemical polymer recovery is due to the production of reproducible analytical signals. A combination of such properties of the electrode as adsorption abilities and the possibilities of electrochemical accumulation can significantly reduce the boundary of the determined contents and increase the expressivity.

The problem is achieved in that the method for the quantitative determination of polyhexamethylene guanidine (PHMG) (anavidin) involves the conversion of anavidin from a sample to a solution by extraction and voltammetric determination using a mercury-film (RP) electrode as an indicator. In this case, accumulation is used for 60–90 s with an electrolysis potential of (0.15–0.3) V relative to 1 M silver chloride electrode against a background of 0.01 M sodium hydroxide with subsequent registration of cathode peaks at a potential sweep speed (80-100 ) mV / s. The concentration of anavidin is determined by the height of the peak in the potential range from –0.8 to –0.95 V using the method of additives of certified mixtures (FIG. 1).

In the proposed method, the ability of anavidin to electrochemical reduction on mercury electrodes is established. An absolute novelty is the experimentally selected background electrolyte of 0.01 M NaOH. The use of the background electrolyte indicated in the claimed invention for the first time made it possible to determine anavidin with a detection limit calculated by the 3-sigma criterion, up to 0.83 · 10 ^-3 mg / l (C _{min, p} ). The minimum detectable concentration (C _n ) of 0.96 · 10 ^-3 mg / l against a background of 0.01 M NaOH (figure 2).

Another distinctive feature is the established conditions of electrochemical accumulation: electrolysis potential E _e = - (0.15 ÷ 0.3) V. Experimental data showed the dependence of the oxidation current of anavidin on E _e (Fig.3). The value of the anode current increased by about 2.4 times and reached its maximum value in the potential region - (0.15–0.3) V. When E _e = - (0.15–0.3) V, the value of the recovery current of anavidin decreased. The use of preliminary electrolysis at potential values of (0.15–0.3) V makes it possible to register voltammograms with a pronounced maximum. This allows you to increase the accuracy and selectivity of the method and expressly determine the concentration of anavidin less than 1 · 10 ^-3 mg / L.

The optimal time of preliminary electrolysis (τ _e ) is 60 ÷ 90 s. When τ _e less than 60 s, the sensitivity of determination decreases and the error of determination increases, and when τ _e more than 90 s the expressivity decreases; the current value reached its maximum value at τ _e equal to 60–90 s.

Important for determining anavidin by the method of adsorption VA is the choice of the potential sweep speed. The optimal speed is (80 ÷ 100) mV / s. Using a speed of less than (80 ÷ 100) mV / s reduces the value of the anode current and lowers the sensitivity of the determination (figure 3).

The established conditions for conducting the electrode process for the first time made it possible to quantitatively determine anavidin based on the electroreduction reaction. To increase the detection sensitivity, preliminary concentration of the substance on the surface of the RP electrode was used. The proposed voltammetric method allowed to quantify anavidin in the range of polymer concentrations from 1 · 10 ^-3 mg / l to 1.0 mg / l.

The measurements were carried out on computerized voltammetric analyzers STA, VAM (LLC ITM, Tomsk).

The determination does not interfere with substances whose presence is possible in biological objects: water-soluble vitamins of groups B (B ₁ , B ₂ , B _c , B ₆ ), PP, ascorbic and uric acids in commensurate amounts. The composition of the matrix of the studied waters has practically no effect on the recovery current of anavidin, therefore, preliminary isolation of the polymer from the matrix was not required prior to the actual electrochemical analysis.

Example 1. The determination of the content of anavidna at the level

(0.1 ÷ 10 ^-3 ) mg / l.

In a quartz glass with a capacity of 20 ml pour 10 ml of a solution of 0.1 M NaOH. Oxygen is removed from the solution by a stream of purified nitrogen with an oxygen content of less than 0.001% within five minutes. Without stopping mixing, the solution is electrolyzed under the condition: E _e = -0.2 V, τ _e = 60 s. The gas is turned off and the cathode voltammogram is recorded at a potential sweep speed of 100 mV / s, starting from potential E _nach = -0.20 V. The absence of peaks indicates the purity of the background. Then add a few drops with a volume of 0.01 ml of a certified mixture of anavidin 0.1-0.01 mg / l, mix the solution for 10 s and conduct electrochemical concentration of the precipitate at E _e = -0.20 V, τ _e = 60 s. The voltammetric curve begins with a potential of -0.20 V. The peak for the indicated substance concentration is recorded in the potential range from -0.80 to -0.95 V (h.s.) with a sensitivity of the device (0.5 ÷ 1) · 10 ^-9 A / mm. The mass concentration of anavidna in the sample is evaluated by the method of additives of certified mixtures, measuring the height of the anode peaks according to the formula (1). A single analysis time does not exceed 15 minutes.

where: X _i - component content in the analyzed sample, g / l;

C _AC is the concentration of the certified mixture (AS) of anavidin, from which the additive to the analyzed sample is made, g / l;

V _AC - the volume of the additive AC component, ml;

I ₁ - the value of the maximum cathode current of the component in the analyzed sample, A;

I ₂ - the maximum cathode current of the component in the sample with the addition of AC, A;

V is the volume of the analyzed sample, ml;

V _ol - the volume of the solution of the prepared sample, ml;

V _al is the volume of an aliquot of the sample solution taken for VA measurement, ml.

Example 2. Determination of the content of anavidin in wastewater

In a quartz glass with a capacity of 20 ml pour 10 ml of a solution of 0.1 M NaOH. Oxygen is removed from the solution by a stream of purified nitrogen with an oxygen content of less than 0.001% within five minutes. Without stopping mixing, the solution is electrolyzed under the condition: E _e = -0.2 V, τ _e = 60 s. The gas is turned off and the cathodic voltammogram is recorded at a potential sweep speed of 100 mV / s, starting from potential E _nach = -0.20 V. The absence of peaks indicates the purity of the background.

In the analysis of wastewater containing trace amounts of anavidna, a sample volume of 3 ml is taken and introduced into an electrochemical cell containing 7 ml of background electrolyte. Electron accumulation and registration of the analytical signal is carried out under the same conditions. The cathode peak of anavidin is fixed in the potential range from -0.85 to -0.95 V on the RP electrode at a sensitivity of the device (1 ÷ 5) · 10 ^-8 A / mm. The mass concentration of anavidna in the sample is evaluated by the method of additives of certified mixtures, measuring the height of the anode peaks according to the formula (1). The analysis time for one sample taking into account sample preparation is less than 20 minutes.

Thus, for the first time, the ability of quantitative chemical analysis of anavidin by the peaks of its restoration at the RP electrode was established.

An analysis of the characteristics of the quantitative chemical determination of anavid by the proposed method indicates a significant increase in the sensitivity of the determination (by 2 orders of magnitude compared to the method of capillary electrophoresis) [Rudnev A.V., Dzheryan T.G. Determination of polyhexamethylene guanidine by capillary electrophoresis // Journal of analytical chemistry, 2006, T.61, No. 10, p.1086-1089]. The detection limit and the lower limit of the determined contents, respectively, are equal to 0.83 · 10 ^-3 mg / l and 0.96 · 10 ^-3 mg / l. Significantly reduced analysis time. The proposed conditions make it possible to control wastewater, air zones of enterprises and chemical laboratories at the level of 0.5 MPC (or less) of anavidin.

The proposed method is simple, does not require a large number of reagents and labor costs and can be applied in any chemical laboratory with a polarograph, especially at the present time, when the production of domestic and foreign electrical equipment with computer control and data processing has been established (analyzers such as STA, TA, etc. ) The proposed method can be used in pharmacokinetic and pharmaceutical studies, in the toxicological and technical analysis of compounds of the guanidine group, for the control of wastewater and air ones input-treatment companies, as well as to develop Anavidin analysis techniques and related compounds in complex multicomponent biological systems (blood, urine, plasma, etc.) and food products.

Claims (1)

The method of quantitative determination of anavidin by inversion voltammetry, including the conversion of anavidin from a sample into a solution and voltammetric determination using a mercury-film electrode, the accumulation of anavidin in a stirred solution is carried out for 60 ÷ 90 s at an electrolysis potential of (0.15 ÷ 0 , 3) In a relatively 1 M silver chloride electrode on the background of a 0.01 M sodium hydroxide solution with subsequent registration of cathode peaks at a potential sweep speed of (80-100) mV / s and concentration Anavidna is determined by the height of the peak in the potential range from -0.8 to -0.95V by the method of additives of certified mixtures.

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