Detection of Cr( III) and Cr( VI) in capsule with spectrophotometry

Objective To develop a new determination method of valence and content of chromium in capsule by spectrophotometry. Methods Capsule was dealt with dry ashing method. Chromium( Ⅲ) was oxidized into chromium( Ⅵ) by ammonium persulfate. The resulting chromium( Ⅵ) can react with diphenylcarbazide to form a purple water- soluble complex,which was determined by spectrophotometry. And the experimental conditions was optimized by single factor method. Results The maximum absorption wavelength of the complex was 540 nm. The linear range of the proposed method was 0. 01 μg / ml ~0. 16 μg / ml. The regression equation was y = 1. 414x- 0. 00127 with a detection limit of 0. 01 μg / ml. The correlation coefficient was 0. 9998. The molar absorptivity for Cr( Ⅵ) was 7. 3 × 104 L /( mol·cm). Relative standard deviation were respectively 4. 3%,3. 6% and 2. 7%,and the spiked recoveries were respectively 98. 6%,100. 4% and 102. 3%. Conclusion The proposed method is simple,sensitive and rapid,and the detection results are satisfactory.