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.