Antihistamines, namely terfenadine and chlorphenoxamine hydrochloride,
react with cobalt and thiocyanate ions to give ternary complexes. The
se complexes are readily extractable in benzene to give a blue colour
with maximum absorption at 625nm. which can be used for quantitative s
pectrophotometric analysis. The mean recoveries for authentic samples
of terfenadine and chlorphenoxamine hydrochloride were 99.9 +/- 0.3 S.
E. and 99.9 +/- 0.3 respectively (P = 0.05). Alternatively, determinat
ion of cobalt content of the benzene extract via atomic absorption spe
ctroscopy provides an indirect method for the determination of these a
ntihistamines. The mean recoveries were 99.33 +/- 0.3 and 99.19 +/- 0.
3 respectively. Both methods were applied to the analysis of pharmaceu
tical preparations, the results obtained agreed well with those obtain
ed by official methods.