Determination of an isomeric impurity in samples of morantel tartrate by gas-liquid chromatographic analysis of the products of a controlled degradation procedure

Abstract

A procedure is described for the determination of the tartrate salt of the 4-methylthienyl isomer of morantel, which is present in samples of morantel tartrate. The procedure involves a controlled degradative oxidation of the ethylene bond that converts morantel and the 4-methylthienyl isomer of morantel into 3-methylthiophene-2-carbaldehyde and 4-methylthiophene-2-carbaldehyde, respectively. Extraction of the two aldehydes is followed by the determination of their relative concentrations by a gas-liquid chromatographic procedure. It is shown that the ratio of the aldehydes given by gas-liquid chromatography is not significantly different from the ratio of morantel to the 4-methylthienyl isomer of morantel present in prepared mixtures of the two isomers. The method is shown to have good precision and to be applicable to morantel samples containing 0·10 to 7·00 per cent. m/m of the 4-methylthienyl impurity.