Determination of Hexavalent Chromium in Solid Waste by Inductively Coupled Plasma-Optical Emission Spectrometry with Microwave Digestion

Abstract

BACKGROUND Hexavalent chromium is one of the necessary indices for monitoring the soil environment of solid waste and construction land. OBJECTIVES To establish a simple, accurate and precise method for the determination of Cr(Ⅵ). METHODS Using 0.1mol/L disodium hydrogen phosphate solution (pH=9.0) as the extractant, the sample was treated by microwave digestion at the optimized temperature and time, ensuring the destruction of the solid sample matrix. All Cr(Ⅵ) in the lattice was dissolved into the solution, and oxidation of Cr(Ⅲ) was effectively inhibited. The hexavalent chromium (solution) and trivalent chromium (precipitation) was separated by 0.45μm filter membrane at pH=9.0. Cr(Ⅵ) in the sample solution, and the content of Cr(Ⅵ) was determined by inductively coupled plasma-optical emission spectrometry (ICP-OES). RESULTS When the sample quantity was 1.00g, the microwave digestion temperature was 90℃, and the digestion time was 20min, the complete extraction and accurate determination of Cr(Ⅵ) in solid waste was guaranteed. The detection limit was 0.057mg/kg, the relative standard deviation (n=7) was lower than 3.20%, compared with HJ 687 standard method, the relative deviation is -5.6%-7.6%, and the recoveries of Cr(Ⅵ) in solid waste were 94.3% and 96.6%. Compared with the previous ICP-OES method with the detection limit of 0.83mg/kg and recovery of 87.2%, the detection limit of this method was lower by 10 times. CONCLUSIONS The proposed method has a lower detection limit, short sample pretreatment time, and high degree of automation and can be widely used in the field of environment monitoring.

Keywords

• cr(ⅵ)
• solid waste
• disodium hydrogen phosphate
• microwave digestion
• inductively coupled plasma-optical emission spectrometry