Analytical Sciences

A Spectrophotometric Determination of Chromium andVanadium

Ashraf A. MOHAMED and Mohamed F. El-SHAHAT

Department of Chemistry, Faculty of Science, Ain Shams University, Abbassia, Cairo, 11566, Egypt

A very simple, selective and sensitive method is developed for the spectrophotometric determination of Cr^VI and/or V^Vbased on their reactions with perphenazine to instantaneously give a red colored product exhibiting a maximumabsorbance at 526 nm. Following the recommended procedure, chromium and vanadium can be determined with linearcalibration graphs up to 0.40 and 1.00 mg ml^-1 and detection limits of 3 and 5 ng ml^-1, respectively. The molarabsorptivities are 1.87x10⁴ and 1.20x10⁴ l mol^-1 cm^-1 with Sandell sensitivity indexes of 2.8 and 4.2 ng cm^-2 for Cr and V,respectively. Analyses of mixtures of Cr^VI and/or V^V in the ratios of 1:100 to 100:1, following the recommended proceduregave recoveries of 97 - 102% with relative standard deviations of 1.4% for both Cr VI and V V . The total Cr and V wasdetermined 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 systematic error and showed the high accuracy andprecision of the method. The unique selectivity and sensitivity of the method allowed its direct application to thedetermination of Cr and V in complex matrices of certified reference materials and synthetic mixtures. The resultsobtained are in excellent agreements with the nominal values.

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