Spectrophotometric Determination of Antioxidant Sodium Metabisulphite Content in Prepared Medicinal Forms of Veterinary Medicinal Products

An analytical method for the quantitative determination of antioxidant sodium metabisulphite in veterinary drugs has been proposed by spectrophotometric method. Based on the literature data, the optimal conditions of the analytical reaction were selected experimentally. The dependence of the value of the analytical signal on the temperature of the reaction medium, concentration of p-rosaniline and duration of the reaction was investigated to establish the optimal conditions of the analytical reaction and obtain a stable analytical signal. The stability of the colored analytical form in time was also checked and the linear dependence of the value of the analytical signal on the concentration of sodium metabisulphite was investigated. The analytical reaction at room temperature is optimal. The maximum analaytical signal is achieved by carrying out the analytical reaction for 10 minutes and then practically does not change for an hour. To achieve the maximum analytical signal, it is necessary to use a 20-fold excess of dye relative to sodium metabisulphite. The analytical signal remains stable only for the first hour, then gradually begins to decrease. Metrological characteristics of the method of determination of metabisulphite in veterinary drugs are calculated, the limits of spectrophotometric determination are 0.33 – 2.50 μg/ml. The correctness of the developed method was checked on model solutions by the method of "introduced-found" method of comparison in the presence of various biologically active substances that are part of drugs together with sodium metabisulphite. The content of sodium metabisulphite in veterinary drugs of domestic and foreign production at different intervals of their storage time was established. It is shown that the content of sodium metabisulphite in drugs decreases during their storage time, until complete disappearance, which directly affects the content of the active substance, because in the absence of antioxidant oxidative processes with biologically active substances begin to take place.