Studies on the Simultaneous Determination of Cr(III) and Cr(VI) by Ion Chromatography (IC)

The research aimed to develop and validate an ion chromatography method for the simultaneous analysis of Cr(III) and Cr(VI) from pumpkin. A new analytical method based on ion chromatography techniques was developed by the Cr(III) pre-column derivatization and Cr(VI) post-column derivatization. The ion chromatography condition was optimized and the detection sensitivity was improved. Cr(III) and Cr(VI) were determined by 365 and 530 nm, respectively. The temperature of water bath, the heating time for pre-column derivatization, and the flow rate of post-column derivative liquid were screened on the basis of single factor experiment, the effects of various factors were determined by the method of L16(43) orthogonal experiment design. Considering the results of orthogonal experiments and the variation tendency of peak area under different factors, the optimum derivatization conditions were chose as follows: the flow rate of post-column derivative liquid is 0.5 mL/min, the temperature of water bath for pre-column derivatization is 100 ℃ and the heating time is 5 min. The conditions were optimized by means of orthogonal experiments under the pH of leacheate ranged from 6.5 to 6.8 and the I– concentration of 5 mmol/L. Under optimized derivatization conditions, the detection limits for Cr(III) and Cr(VI) were 0.17 and 0.019 mg, respectively. And the average recoveries of Cr(III) in pumpkin were in the range of 82%-85%. Results indicated that pumpkin does not contain Cr(VI) according to this ion chromatography method of simultaneously determination for Cr(III) and Cr(VI).