Determination of Chromium in Soil Samples by Arsenazo III Fading Spectrophotometry

In the nitric acid solution,chromium(Ⅵ) reacts with arsenazo Ⅲ to produce a sensitive color-fading reaction.Based on this fact,a discoloring spectrophotometric method was developed to determine chromium(Ⅵ) in soil.The maximum determination wavelength of the discoloration system is 545 nm with the molar absorption coefficient of 4.67×104 L/(mol·cm).The measured data accorded with Beer′s law when the chromium(Ⅵ) concentration was lower from 0 to 0.8 μg/mL.The method was used in the determination of chromium in soil samples,and the relative standard deviation(RSD) is less than 3.1%(n=6).The obtained results by fading spectrophotometry were in good agreement with those by atomic absorption spectrometry.