Spectrophotometric Determination of Chromium in Water, and Pharmaceutical Samples Using 1‐Naphthol

Abstract

Facile and sensitive spectrophotometric methods for the determination of trace and ultra trace amounts of chromium (VI) are described. 4‐aminoantipyrine (APP) reacts with 1‐naphthol (NPL) in presence of oxidising agent potassium dichromate in acidic medium to produce red coloured product having λ max of 485 nm. The molar absorptivity and Sandell′s sensitivity were 2.07x10 4 l mol -1 cm -1 and 0.00240 μg/cm 2 respectively. The colour is stable for more than 6 h. The system obeys Beer′s law in the range, 2‐18 μg for determination of chromium (VI). The detection limits of chromium (VI) is 0.048 μg mL -1 . The method is highly reproducible and has been applied to the analysis of chromium in synthetic, natural water samples and pharmaceutical preparations and the results compared favourably with the reported method.