Determination of High-Level Hexavalent Chromium in Chromium Slag Field Soils by Inductively Coupled Plasma-Optical Emission Spectrometry with Alkaline Extraction

The hexavalent chromium Cr(Ⅵ) content in chromium slag field soils typically ranges from tens to thousands of mg/kg, far exceeding the background values of ordinary soils and exhibiting complex matrices. Existing methods for determining high-level Cr(Ⅵ) in such contaminated sites are susceptible to matrix interferences. This study introduces a synergistic extraction method based on the industrial standard HJ 1082-2019 alkaline extraction solution, enhanced by the addition of EDTA chelating agent and Triton X-100 surfactant. This method improves extraction efficiency and suppresses Cr(Ⅲ) oxidation through dual mechanisms of chemical chelation and physical dispersion. Optimal extraction conditions, determined via orthogonal experiments, include: 12 mL alkaline extraction solution, 90°C extraction temperature, 80 min extraction time, 3 mL Triton X-100, 12 mL EDTA, and a solid-to-liquid ratio of 1∶54 (g:mL). Under the optimal extraction conditions, the recovery rate of Cr(Ⅵ) in soil reached 96.8%, and the number of extractions was reduced from 6 times in the HJ 1082-2019 standard method to 2 times in this method. Cr(Ⅵ) quantification was performed using inductively coupled plasma-optical emission spectrometry (ICP-OES), with high-salt matrix interferences mitigated by adding 2.0 g of 001 × 7 strong acid cation exchange resin. The method exhibited excellent linearity (0−8.00 mg/L), a detection limit of 0.30 mg/kg, a quantification limit of 1.01 mg/kg, and an upper detection limit of 3200 mg/kg. Validation using certified reference materials GBW(E)070255, RMH-A043 and two high-content Cr(Ⅵ) self-prepared samples demonstrated close agreement between measured and certified values (relative errors from −2.87% to −0.69%) and low relative standard deviations (RSD < 5.00%). Compared to flame atomic absorption spectrometry, this method offers superior matrix interference resistance and broader applicability, and has been successfully applied to Cr(Ⅵ) determination in soils from a chromium slag field in North China. The BRIEF REPORT is available for this paper athttp://www.ykcs.ac.cn/en/article/doi/10.15898/j.ykcs.202503170047.