Facile colorimetric methods for the quantitative determination of tetramisole hydrochloride

A facile, rapid and sensitive methods for the determination of tetramisole hydrochloride in pure and in dosage forms are described. The procedures are based on the formation of coloured products with the chromogenic reagents alizarin blue BB (I), alizarin red S (II), alizarin violet 3R (III) and alizarin yellow G (IV). The coloured products showed absorption maxima at 605, 468, 631 and 388 nm for I-IV, respectively. The colours obtained were stable for 24 h. The colour system obeyed Beer's law in the concentration range 1.0-36, 0.8-32, 1.2-42 and 0.8-30 microg ml(-1) respectively. The results obtained showed good recoveries with relative standard deviations of 1.27, 0.96, 1.13 and 1.35%, respectively. The detection and determination limits were found to be 1.0 and 3.8, 1.2 and 4.2, 1.0 and 3.9 and finally 1.4 and 4.8 ng ml(-1) for I-IV complexes, respectively. Applications of the method to representative pharmaceutical formulations are represented and the validity assessed by applying the standard addition technique, which is comparable with that obtained using the official method.