A spectrophotometric determination of chromium and vanadium

A very simple, selective and sensitive method is developed for the spectrop hotometric determination of Cr-VI and/or V-V based on their reactions with perphenazine to instantaneously give a red colored product exhibiting a max imum absorbance at 526 nm. Following the recommended procedure, chromium an d vanadium can be determined with linear calibration graphs up to 0.40 and 1.00 mu g ml(-1) and detection limits of 3 and 5 ng ml(-1), respectively. T he molar absorptivities are 1.87x10(4) and 1.20x10(4) 1 mol(-1) cm(-1) with Sandell sensitivity indexes of 2.8 and 4.2 ng cm(-2) for Cr and V, respect ively. Analyses of mixtures of Cr-VI and V-V in the ratios of 1:100 to 100: 1, following the recommended procedure gave recoveries of 97 - 102% with re lative standard deviations of less than or equal to 1.4% for both Cr-VI and V-V. The total Cr and V was determined first; then, V was determined after addition of As-III to reduce Cr-VI that was calculated by the difference. Statistical treatment of the analytical results did not detect any systemat ic error and showed the high accuracy and precision of the method. The uniq ue selectivity and sensitivity of the method allowed its direct application to the determination of Cr and V in complex matrices of certified referenc e materials and synthetic mixtures. The results obtained are in excellent a greements with the nominal values.