Spectrophotometric Determination of Chromium Using Promethazine Hydrochloride - Application in Various Samples

A rapid, simple and sensitive spectrophotometric method for the determination of trace amounts of chromium (VI) was studied. The method is based on the reaction of chromium (VI) with promethazine forming a red colored species by chromium in hydrochloric acid medium and exhibits a maximum absorbance at 518 nm. A plot of absorbance with chromium (VI) gives a straight line indicating that Beer’s law has been obeyed over the range concentration of 0.05-4.0 μg/ml with a molar absorptivity of chromium(VI) 2.04  104 l.mol-1.cm-1 , Sandell’s sensitivity index of 0.0025 μg.cm-2 while the limit of detection (LOD) was found to be 0.0924 μg.ml-1 and a relative standard deviation of (0.63-1.24)%,depending on the concentration level. The method is developed for the determination of chromium (III) and has been successfully applied to the determination of chromium in various water samples, pharmaceutical preparations, synthetic alloys and standard rock sample of known composition (MRG-1).