Simultaneous determination of sulphamethoxazole and trimethoprim in co-trimoxazole tablets by first-derivative FTIR spectrometry

A first-derivative FTIR spectrometric method has been developed for the sim ultaneous determination of sulphamethoxazole (SMX) and trimethoprim (TMP) i n their binary dosage formulations. The procedure is based on extraction of active components in a solution of 30% v/v acetone in chloroform, filtrati on and measurement of the amplitudes of the first derivative spectrum at 11 38 and 1166 cm(-1) for TMP and SMX respectively. Good linearity, accuracy a nd precision were found for this method. The relative standard deviation fo r TMP and SMX were found to be 1.5 and 1.3% in a commercial Co-trimoxazole tablet, respectively (n=5).