ELECTROREDUCTION AT SOLID ELECTRODE MATERIALS AND VOLTAMMETRIC DETERMINATION OF POTASSIUM HYDROGENPEROXOMONOSULFATE

The electrochemical behaviour of potassium hydrogenperoxomonosulfate (KHSO5) at carbositall and Au, Ag electrodes using the square-wave voltammetry (SWV) with 0.2 mol L–1 KHSO4 background solution (pH ~ 0.8) (Ep = 0.25 V vs 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 to determine the peroxomonosulfate in model solutions on the studied electrodes was shown

OXIDATION-REDUCTION POTENTIAL OF THE SYSTEM OF PEROXOMONOSULPHATE/SULPHATE AND ITS DEPENDENCE ON THE PHMEDIUM

The electrochemical generalized equation of the protonic particles interaction of the oxidized and reduced forms of peroxomonosulphate/sulphate system was derived and the theoretical interpretation of the oxidation-reduction potential dependence on pH medium was given. It is shown that at the change in pH value the nature of chemical particles changes, consequently, the form of the electrochemical generalized equation transforms that brings to the dependence of oxidation-reduction potential dependence on medium pH. The numerical calculation of the dependence of E on pH was performed

APPLICATION OF THE KINETIC ENZYMATIC METHOD FOR BENZALKONIUM CHLORIDE DETERMINATION IN AN AEROSOL PREPARATION

A new kinetic photometric method for BAC determination based on inhibition of the enzymatic (cholinesterase) reaction was proposed. The reaction rate was detected at unhydrolised acetylcholine residue, which is determined by the amount of peracetic acid, produced during the impact of H2O2 on it. Indicator reaction is a reaction of peracetic acid with 4-ethoxyaniline interaction that leads to the formation of azoxyphenetole with λmax = 358 nm (lgε =4.18). The measurement of the velocity of changes in the light absorption vs. time (∆А/∆t, min-1) gives the chance to quantitatively determine the BAC. The results have confirmed that the method is linear at concentrations ranging from 1.0×10-6 mol/L to 5.0 ×10 -6 mol/L. Depending calibration equation ΔA/Δt, min-1 has the form: tgα = 5093 c + 0.0075 (r = 0,999). LOD was 0.4× 10-6 mol/L. The method was successfully applied to determine BAC in nasal pharmaceutical preparation «Aqua-rinosol». The recovery was 99.9%, RSD = 2.7 % (n=5, P=0.95). This method is beneficial because the high sensitivity and selectivity can be achieved using the relatively simple technical equipment

Iodometric determination of cystamine dihydrochloride in tablets using diperoxyadipic acid

The kinetics of cystamine dihydrochloride oxidation by diperoxyadipic acid (DPAA) was studied in aqueous buffer solutions of pH 2.9, 6.9, 8.0, 8.5 and 9.2 under second-order conditions at the temperature 293 K. The second order rate constants, k (L mol−1 min−1) were calculated from kinetic values. A suitable mechanism scheme based on these observations was proposed. The possibility of application of DPAA as reagent for oxidimetric determination of cystamine dihydrochloride in tabtets was investigated. Cystamine dihydrochloride was determined by indirect titration with DPAA. The required amount of Cystamine dihydrochloride was dissolved in water, pH 8.0 buffer solution and DPAA solution was added. After 7 min, the solution was acidified. The excess DPAA was determined via iodometric titration. The advantages of the applied analytical techniques in the determination of cystamine dihydrochloride in tablets «Cystamine 0.2 g» was presented. The recovery of сystamine dihydrochloride was 99.32±1.45%. A paired t-test showed that all results obtained for bulk drug and in tablets «Cystamine 0.2 g», using the proposed procedure and the official procedure respectively, agreed at the 95% confidence level

Quantitative determination of Levomepromazine in pharmaceuticals by spectrophotometric method as its sulfoxide

The oxidative derivatization method using Diperoxyazelaic acid for the indirect spectrophotometric determination of Levomepromazine hydrochloride is presented. Diperoxyazelaic acid is introduced as a derivatizing agent for Levomepromazine, yielding the sulfoxides. This reaction product was successfully used for the spectrophotometric determination of the Levomepromazine hydrochloride. The UV spectroscopic detection of the sulfoxide proved to be a more robust and sensitive method. The elaborated method allowed the determination of Levomepromazine hydrochloride in the concentration range of 3-150 µg/mL. The limit of quantification, LOQ (10S) is 2.85 µg/mL. A new spectrophotometric technique was developed and the possibility of quantitative determination of Levomepromazine in Tisercin Solution for Injection 25mg/mL was demonstrated. The present method is precise, accurate and other excipients: anhydrous citric acid, monothioglycerol, sodium chloride did not interfere. RSD = 1.24 % (δ = –0.02 %)

A new oxidative derivatization method for spectrophotometric determination of Periciazine in pharmaceutical preparations

A new the oxidative derivatization method by means of peroxoacid for the indirect spectrophotometric determination of Periciazine is presented. A potassium hydrogenperoxymonosulfateas a derivatizing agent for Periciazine, yielding the absorbative Periciazine sulfoxide at λmaх=362 nm is proposed. This reaction product was successfully employed for spectrophotometric determination of the Periciazine. The UV spectrophotometric determination of the Periciazine as its sulfoxide proved to be the more simple and selective method. Limit of quantification (LOQ=10S) is 2.8 µg·mL-1. The common excipients employed do not interfere in the determination of phenothiazine drug. Results of analysis of the drug dosage forms by the proposed method are in good agreement with those of the official method. RSD=1.76 % (δ <RSD)

COMPARATIVE STUDY OF THE ANTIBACTERIAL ACTIVITY OF OINTMENT BASED ON DIPEROXYAZELAIC AND UGRESOL 10% AND ACNE STOP 20% PREPARATIONS

The diperoxyazelaic acid was synthesised. Ointment on the polyethylenoxide basis containing 1% diperoxyazelaic acid was obtained. The antimicrobial activity of the ointment and branded drugs Acne Stop and Ugresol have been explored in the comparative perspective. The shelf life of creams was clarified. The conclusion was made about the prospects for further in-depth research on the issue of its application as the extemporal dosage form

Comparación de tres métodos independientes para la detección de cefalexina usando el potasio de caroata

ABSTRACT Aims.Three different assays for the quantity determination of Cephalexin in pure substance were developed and compared using potassium caroate as analytical reagent. Materials and Methods. Cephalexin pure substance was used and analytical reaction by means of KHSO5 as an oxidant was studied. Voltammetric, kinetic-spectrophotometric and iodometric methods were developed and validated. Results. The chemical reaction is finished with formation of the S-oxide of Cephalexin in the iodometric and voltammetric methods and the S-oxide hydrolysis product in the kinetic-spectrophotometric method. The reaction finishes in 1 min (observation time). The methods have been validated and good results including precision, accuracy and recovery were obtained. The recovery percent ranged from 98.7 to 101.4%, RSD from 1.42 to 3.0%. The methods proposed are linear in a wide range: voltammetry 2-45 μg mL-1, kinetic-spectrophotometry 1-16 μg mL-1, and iodometry 0.05-0.35 mg mL-1. LOD and LOQ were calculated. The kinetic-spectrophotometric method is the most sensitive (LOQ=1.0 μg mL-1). Conclusions. The methods proposed are rapid, simple and inexpensive and could be applied to pharmaceutical preparationRESUMEN Objetivo. Se han desarrollado tres métodos diferentes para la detección cuantitativa de Cefalexina en producto puro, usando el caroata de potasio como un reactivo analítico. Materiales y métodos. Fue estudiada la reacción analítica de cefalexina con KHSO5 como oxidante. Se han desarrollado y validado los métodos de voltamperimetría, de espectrofotometría cinética y de iodometría. Resultados. La reacción química se completa con la formación de s-óxido de Cefalexina dentro de los métodos de iodometría y de voltamperometría, y con la formación del producto de hidrólisis de s-óxido en el método de espectrofotometría cinética. La reacción se completa en 1 minuto (tiempo de observación). Los métodos han sido validados, y se han obtenido resultados buenos, incluida la exactitud, la fiabilidad y la reproducibilidad. El contenido de la sustancia básica oscila desde 98,7% hasta 101,4%. El RSD está entre 1,42 y 3,0%. Los métodos propuestos son lineales en un amplio espectro: la voltamperometría 2-45 μg ml-1, la espectrofotometría cinética 1-16 μg ml-1, y la iodometría 0,05-0,35 mg ml-1. Han sido calculados el límite de detección y el límite de cuantificación. El método de espectrofotometría cinética es el más sensible (el límite de cuantificación = 1,0 mcg ml-1). Conclusiones. Los métodos propuestos son rápidos, simples y baratos, y pueden ser utilizados en las preparaciones farmacéuticas.The research work performed in the manuscript is done on the funding of National University of Pharmacy (Ukraine

Quantitative Determination of Lincomycin in Dosage Forms by Iodometric Titration through Oxidation Reaction with Peroxomonosulfate

The kinetics of the oxidation reaction of Lincomycin hydrochloride (Link) with potassium hydrogen peroxomonosulfate (KHSO5) was studied depending on the pH of the medium. It has been established that the reaction kinetics obeys the general laws of specific acid-base catalysis. KHSO5 reacts quantitatively with Link in an alkaline medium to form the corresponding sulfone-N-oxide: 1 mole of Link requires 3 moles of KHSO5. Methods for the oxidimetric determination of Link were developed using KHSO5 as an analytical reagent: a known excess of the reagent is added and after a specified time, its residual amount is determined by iodometry. The possibility of quantitative determination of the main substance in the substance of Link hydrochloride, as well as the determination of Link hydrochloride solution for injection "Lincomycin-Zdorovye" 300 mg/ml in ampoules of 1 ml and capsules of 0.25 g were shown. RSD does not exceed 1.7%

Development and Validation of a Simple Procedure for the Kinetic Spectrophotometric Quantitative Determination of Ceftriaxone Using Potassium Caroate

A simple procedure for the quantitative determination of the Ceftriaxone pure substance by the spectrophotometric method in its kinetic modification using Caro’s acid has been developed and validated. The scheme of the chemical transformation of Ceftriaxone with the reaction of potassium caroate has been proposed. The appearance of a new wave gives the possibility of developing a new procedure for the quantitative determination of Ceftriaxone. The obtained results of accuracy and precision are as follows: RSD = 1.63-2.25 %, δ = 0.33-0.96 %. LOD = 0.1 µg/mL, LOQ = 0.33 µg/mL