A New Colorimetric Identification of Benzodiazepines: Using Cobalt Thiocyanate as Reagent

A highly specific, easy to perform and cost effective color test for benzodiazepines class has been developed. This colour test produced green colour with eight benzodiazepines i.e. nitrazepam, temazepam, diazepam, bromazepam, clonazepam, estazolam, lormetazolam and alprazolam, whereas developed color was absent in other controlled or pharmaceutical substances tested during study. In this color test, one drop of concentrated hydrochloric acid was added to test substrate. Then two drops of cobalt thiocyante reagent were added in subsequently which resulted in an immediate appearance of green color. So this test can be very helpful as a presumptive screening tool for benzodiazepines testing in suspected illicit samples and pharmaceuticals. Moreover, this test can be further employed for diazepam quantitation using ultraviolet spectroscopy at 364 nm wavelength and showed linear detector response. A regression co-efficient value of 0.9996 was achieved using developed method and was effectively useful for diazepam quantitation in pharmaceutical dosage forms.