RU2246722C1 - Inversion voltampermetric method of determining concentration of amiodarone (cordarone) - Google Patents

Abstract

FIELD: analytical chemistry.

SUBSTANCE: substance is subject to preliminary concentrating during 300 sec at potential of electrolysis of (-1,2) V by using special device. Glass-carbon electrode is used as working electrode. Polarization curves are registered subsequently at ac potential development at speed of 300 mV/sec. Concentration of amiodarone is found from peak value within the potential range of 0,1-0,3 V relatively chlorine-silver electrode in 0,005 mole/l nitrate ammonium solution that is prepared on the base of 0,015 mole/l sodium hydrocarbonate solution.

EFFECT: improved sensitivity of method.

1 dwg, 4 tbl

Description

The invention relates to the field of analytical chemistry, in particular to an inverse voltammetric method for determining the drug substance amiodarone (cordarone, [2-butyl-3-benzofuranyl] - [4- (2-diethylaminoethoxy) -3,5-diiodophenyl] ketone hydrochloride), and can be used in medicine to determine the concentration in the blood of amiodarone, which is an antiarrhythmic drug of class III.

Amiodarone, being the main representative of class III antiarrhythmic drugs, has a characteristic effect on the electrophysiological properties of the myocardium. It significantly lengthens the action potential of cardiomyocytes (due to prolongation of repolarization) and, thus, increases the effective refractory period of the atria, ventricles, atrial ventricular node, His bundle and Purkinje fibers, as well as additional pathways for conducting excitation. In the molecular mechanism of antiarrhythmic action of amiodarone, a certain role may be played by its ability to block potassium channels of cell membranes. It exhibits non-competitive antagonism to α and β receptors. As an antiarrhythmic agent, amiodarone is used to stop and prevent life-threatening ventricular arrhythmias, as well as supraventricular arrhythmias, refractory to commonly used therapy, especially associated with Wolf-Parkinson-White syndrome, including paroxysmal fibrillation and atrial flutter, ectonic tachycardia; arrhythmias against the background of coronary or heart failure; there is evidence that the drug is effective for parasystole [1; 2; 3].

Quantification of amiodarone is relevant in assessing the effectiveness of the treatment of diseases of the cardiovascular system.

Information on the quantitative determination of trace amounts of amiodarone by inversion voltammetry is not available.

The closest method is the inverse voltammetric determination of the drug digoxin, taken as a prototype. The determination of digoxin consists in the electrochemical concentration of digoxin on the surface of a mercury-film electrode for 180 s. With an electrolysis potential of (-1.80) - (- 1.75) V against a background of 0.2 n. lithium chloride with subsequent registration of current-voltage curves at a potential sweep speed of 20 mV / s, and the concentration of digoxin is determined by the height of the peak in the potential range (-1.10) - (- 1.00) V relative to the silver-silver electrode [4]. Using the conditions described in the prototype method does not provide the sensitivity and expressivity of the determination of amiodarone in model mixtures and biological fluids.

The aim of the invention is to increase the sensitivity and expressivity of the method for determining amiodarone by inversion voltammetry.

The goal is achieved by a technical solution, which is the determination of amiodarone by inversion voltammetry on a TA-2 device, by recording polarization curves with preliminary electrochemical concentration of the substance on the electrode surface. To do this, nitrogen with an oxygen content of less than 0.001% is passed through the solution and, without stopping mixing, the solution is electrolyzed at a potential of (-1.2) V for 300 s. A glass-carbon electrode is used as a worker. Then, the registration of polarization curves is carried out at a constant-current form of potential sweep at a speed of 300 mV / s. The concentration of amiodarone is determined by the height of the peak in the potential range from 0.1 V to 0.3 V, relative to the silver-silver electrode. The determination is carried out against a background of a 0.005 mol / L solution of ammonium nitrate prepared in a 0.015 mol / L solution of sodium bicarbonate.

New in the method is that a preliminary electrochemical accumulation of amiodarone is carried out at an electrolysis potential equal to (-1.2) V, on a TA-2 device for 300 s. A glass-carbon electrode is used as the working electrode. Registration of polarization curves is carried out at a constant-current form of a potential sweep at a speed of 300 mV / s, and the concentration of amiodarone is determined by the height of the peak in the potential range from 0.1 V to 0.3 V relative to a silver-silver electrode against a background of a 0.005 mol / L solution ammonium nitrate prepared in a 0.015 mol / L sodium bicarbonate solution.

Distinctive features showed new properties in the claimed combination: an increase in sensitivity (10 ^-6 -10 ^-7 mg / l) and the expressness of the analysis.

In view of the above, the claimed solution should be considered as meeting the criterion of “substantial differences”.

All conditions for the determination of amiodarone are selected experimentally. The preparation of background and standard solutions of organic matter in water are common.

In the process of searching for optimal conditions for the inversion voltammetric determination of amiodarone, the influence of a number of factors (indicator electrode, background electrolyte, its concentration and pH, time and potential of electrolysis, boundaries and sweep potential) on the height of the analytical signal was studied (Table 1-3).

As background electrolytes, solutions of ammonium nitrate, sodium hydrogen phosphate mono- and disubstituted, potassium chloride, lithium chloride, sodium bicarbonate, calcium chloride with the addition of diluted sulfuric, hydrochloric, tartaric acids were investigated; sodium bicarbonate, sodium and potassium hydroxides. Based on the results obtained, a solution of ammonium nitrate was chosen as the background electrolyte, since a clear oxidation wave of amiodarone was observed on it, in addition, this solution provided good electrical conductivity, a wide working area and the necessary area for signal processing, it was easy to prepare, to the advantages also include the long shelf life.

The optimal concentration of ammonium nitrate solution was 0.005 mol / L. In more concentrated solutions, we did not observe an increase from the additive in the presence of a large residual current, while a more dilute solution was unstable in time.

The optimal pH of the background electrolyte was 8.0, which provided sodium bicarbonate at a concentration of 0.015 mol / L. In the acidic medium under the selected conditions, the amiodarone signal was absent, while in the neutral one it was weakly expressed, when the pH changed to a more alkaline side (more than 8.0), the working region of the electrode narrowed, and it was impossible to fix the peak of amiodarone. The optimal alkalizing agent was sodium bicarbonate, since no reproducibility of the results was observed in the presence of sodium hydroxide and potassium hydroxide.

In the proposed method, glass-carbon was used as an indicator electrode. The advantage of such an electrode is the possibility of obtaining narrower and higher peaks that serve as the analytical characteristic of the analyte, which increases the resolution of the method. Amiodarone is easily adsorbed on the working surface of glassy carbon; this allows it to be concentrated on an electroactive electrode.

The optimal accumulation time was 300 s, while achieving the maximum value of the dissolution current of accumulated sediments from the surface of the glass-carbon electrode and good reproducibility for the quantitative determination of the test substance. When the electrolysis time is more than 300 s, the deposit saturates on the electrode, the analytical signal of amiodarone is distorted and the processing of polarograms is difficult. When the electrolysis time is less than 300 s, the dissolution current does not reach the maximum value, which reduces the sensitivity of the determination of a substance (Table 1).

Another distinguishing feature is the established conditions of electrochemical accumulation. The optimal electrolysis potential was (-1.2) V. In the prototype, the range of electrolysis potentials corresponds to (-1.80) - (- 1.75) V, which does not allow amiodarone to accumulate on the indicator electrode. At values of the electrolysis potential less than (-1.2) V, the value of the registered anode current decreases significantly, which decreases the detection sensitivity, and at values of the electrolysis potential greater than (-1.2) V, a partial accumulation of sediment occurs (Table 2).

An important inversion of voltammetric determination of amiodarone is the choice of potential sweep speed. Optimum experimentally established is 300 mV / s. A change in the potential sweep rate in the direction of increasing or decreasing markedly reduced the height of the analytical signal, while the resolution of the method also decreased, which complicated the processing of polarograms, increased the analysis time, and did not allow determination of very low concentrations of amiodarone (Table 3).

Example 1. Determination of amiodarone by inversion voltammetry in solution.

In a quartz glass with a capacity of 20 ml, pour 10 ml of a 0.005 mol / L solution of ammonium nitrate prepared in a 0.015 mol / L solution of sodium bicarbonate. At a potential of (-1.2), the solution is deaerated with nitrogen with an oxygen content of less than 0.001% for 30 s and, without stopping stirring, electrolysis is carried out at a potential of (-1.2) V for 300 s. They turn off the gas and record the voltammogram at a constant-current form of potential sweep at a speed of 300 mV / s. The absence of peaks indicates a clean background.

Then add N drops with a volume of 0.01 ml of a standard solution of amiodarone 0.1 mg / l, mix the solution and conduct electrochemical concentration of the substance at a potential of (-1.2) V for 300 s. They turn off the gas and record the voltammogram at a constant-current form of potential sweep at a speed of 300 mV / s. The analytical signal for the indicated concentration of amiodarone is recorded in the potential range from 0.1 V to 0.3 V.

The time of a single analysis does not exceed 20 minutes.

The established conditions made it possible for the first time to quantify amiodarone by recording current-voltage curves at a potential of (-1.2) V against a background of a 0.005 mol / L solution of ammonium nitrate prepared in a 0.015 mol / L solution of sodium bicarbonate. The lower limit of the determined concentrations of amiodarone is 10 ^-7 mg / L.

The relative error of an individual variant (ε) for a concentration range of 1000-0.01 mg / l does not exceed 5% (Table 4).

The established experimental conditions for the determination of amiodarone by the method of inverse voltammetry make it possible to determine the indicated compound in aqueous and biological media with high sensitivity and expressness, and also allow us to develop a method for determining the content of microquantities of amiodarone in plasma and blood serum.

Table 1
INFLUENCE OF ELECTROLYSIS TIME ON THE ALTITUDE OF THE AMYODARON ANALYTICAL SIGNAL No. p / p The concentration of a solution of a standard sample of amiodarone in an electrolytic cell, mg / l Electrolysis time, s Analytical signal height, μA 1 thirty 0.237 ± 0.014 2 60 0.242 ± 0.005 3 90 0.495 ± 0.004 4 120 1,111 ± 0,006 5 150 1.302 ± 0.001 6 180 1.537 ± 0.002 7 210 1.895 ± 0.007 8 240 2,470 + 0,004 nine 270 2.753 ± 0.003 10 4.97510 ^-4 300 3.007 ± 0.002 eleven 330 2,990 ± 0,005 12 360 2.941 ± 0.002 thirteen 390 2,906 ± 0,001 14 420 2,856 ± 0,007 fifteen 450 2,505 ± 0,003 16 480 2,496 ± 0,004 17 510 2,350 ± 0,004 eighteen 540 2.285 ± 0.008 19 570 2.272 ± 0.011 twenty 600 2.264 + 0.010 Note: The electrolysis potential is (-1.2) V;
potential sweep boundaries from (-1.2) to 0.7V;
potential sweep speed - 300 mV / s.

table 2
INFLUENCE OF THE POTENTIAL OF ELECTROLYSIS ON THE ALTITUDE OF THE AMYODARON ANALYTICAL SIGNAL No. p / p The concentration of a solution of a standard sample of amiodarone in an electrolytic cell, mg / l Electrolysis Potential, V Analytical signal height, μA 1 -1.70 1.379 ± 0.073 2 -1.60 1.513 ± 0.011 3 -1.50 1.618 ± 0.007 4 -1.40 1.854 ± 0.010 5 -1.30 2.615 ± 0.006 6 -1.20 3.007 ± 0.002 7 -1.10 2.670 ± 0.005 8 -1.00 2.257 ± 0.003 nine 4.97510 ^-4 -0.90 1,640 ± 0,003 10 -0.80 1.514 ± 0.001 eleven -0.70 1.479 ± 0.008 12 -0.60 1.407 ± 0.009 thirteen -0.50 1.279 ± 0.004 14 -0.40 1,091 ± 0,001 fifteen -0.30 0.547 ± 0.007 16 -0.20 0.369 ± 0.003 17 -0.10 0.184 ± 0.008 eighteen 0 0.101 ± 0.010 Note: Electrolysis time - 300 s;
potential sweep boundaries from (-1.2) to 0.7V;
potential sweep speed - 300 mV / s.

Table 3
INFLUENCE OF CAPACITY SPEED SPEED ON THE ALTITUDE OF THE AMODARON ANALYTICAL SIGNAL No. p / p The concentration of a solution of a standard sample of amiodarone in an electrolytic cell, mg / l Potential sweep speed, mV / s Analytical signal height, μA 1 fifty 0.327 ± 0.012 2 100 0.774 ± 0.009 3 4.97510 ^-4 150 1.278 ± 0.008 4 200 1,627 ± 0,003 5 250 2.536 ± 0.004 6 300 3.007 ± 0.002 7 350 2.915 ± 0.001 8 400 2.826 ± 0.002 Note: Electrolysis time - 300 s;
electrolysis potential - (-1.2) V;
potential sweep boundaries from (-1.2) to 0.7V.

SOURCES OF INFORMATION

1. Prevention of paroxysms of atrial fibrillation with amiodarone in patients on an outpatient basis. / B.Ya. Bart, O.L. Smirnova, V.G. Larin and others. // Cardiology. - 1997. - T.37, No. 3. - S.33-36.

2. Mashkovsky M.D. Medicines In 2 volumes. - 14th ed. / M.D. Mashkovsky. - M .: OOO “Publishing house new wave”, 2001. - T.2. - S. 371-373.

3. Shabalin A.V. The effect of amiodarone on the vegetative status and its effectiveness in the treatment of different variants of paroxysmal atrial fibrillation / A.V. Shabalin, Yu.S. Shaposhnikova, I.A. Guseva // Cardiology. - 2002. - T. 42, No. 8. - S.25-30.

4. Ivanovskaya E.A. Quantitative determination of digoxin in serum by inversion voltammetry // RF Patent No. 21322553.

Claims (1)

The method for determination of amiodarone (cordarone, [2-butyl-3-benzofuranyl] - [4- (2-diethylaminoethoxy) -3,5-diiodophenyl] ketone hydrochloride) by the method of inverse voltammetry, which consists in the electrochemical concentration of a substance on the surface of the electrode with subsequent registration current-voltage curves, characterized in that the concentration is carried out on a glassy carbon electrode for 300 s with an electrolysis potential of -1.2 V against a background of a 0.005 mol / L solution of ammonium nitrate prepared in a 0.015 mol / L solution of sodium bicarbonate, followed by boiling unregistering voltage curves under constantly-shaped current potential sweep rate of 300 mV / s, and the concentration of amiodarone is determined by the peak height in the potential range 0.1-0.3 V relative to silver-silver chloride electrode.