Sensitive electron-capture gas-liquid chromatographic assay for the de-ethylated metabolite of metoclopramide.

A procedure is described for determining 4-amino-5-chloro-2-methoxy-N-(2-ethylaminoethyl)benzamide, a metabolite formed by de-ethylation of metochlopramide, in urine from rats. The sampe is extracted (at pH approximately 13) with chloroform and, after treatment with heptafluorobutyric anhydride, derivatives of the extracted compounds are analyzed by gas-liquid chromatography, with electron-capture detection and diazepam as internal standard. The drug and its metabolite are separated, and the latter can be determined in the range 0.4 to 1.85 microgram/ml in the sample. The behaviour of the metabolic during chemical-ionization and electron-impact mass spectrometry is discussed.