微波消解火焰原子吸收光谱法测定土壤中六价铬

目前用于土壤中六价铬检测的提取方法较为单一，一般是使用HJ 1082—2019《土壤和沉积物 六价铬的测定 碱溶液提取-火焰原子吸收分光光度法》中提到的碱溶液提取法. 但该方法在进行大批量土壤检测时存在耗时长、试剂用量大、温度不易控制等问题. 因此，建立高效、准确的土壤中六价铬测试方法，对开展土壤中六价铬污染风险评价及修复工作具有十分重要的意义. 本研究提出了微波消解火焰原子吸收光谱法，用于快速、准确测试土壤中六价铬. 通过开展提取剂组成与用量、微波消解方式、消解液过滤及pH调整等参数优化研究，确定了土壤中六价铬提取与测试的优化条件:消解液组成为碱性提取液20 mL、氯化镁100 mg、磷酸氢二钾-磷酸二氢钾缓冲溶液0.2 mL，3次微波消解，消解液用中速定量滤纸过滤，待测液pH调节至7.0~8.0. 在优化条件下，土壤六价铬的有证标准样品的测量结果均在标准值范围内，土壤基体加标回收率为85.5%~88.7%，相对标准偏差为7.6%~8.0%. 与HJ 1082—2019相比，本文建立的微波消解火焰原子吸收光谱法更适用于大批量土壤样品的六价铬检测分析，所采用的微波消解技术，操作相对简单、提取效率较高，易于在不同种类实验室中普及和推广，可为土壤中六价铬的快速准确检测提供技术支持和方法补充. 

Developments of the Method of Microwave Digestion and Flame Atomic Absorption Spectrometry for Determination of Hexavalent Chromium in Soils

The alkali solution extraction method is commonly used to extract hexavalent chromium in soils, according to the standard for Alkali Solution Extraction-Flame Atomic Absorption Spectrophotometry (HJ 1082-2019). This method has some problems for the detection of batch soils, including long extraction time, high reagent consumption, and large temperature variations. Therefore, it is highly desirable to develop a determination method of hexavalent chromium in soils with high efficiency and accuracy for risk assessments and remediation decisions of hexavalent chromium in soils. In this study, we developed a microwave digestion-flame atomic absorption spectrometry method of hexavalent chromium in soils. By conducting the effect experiments of extraction agents, microwave digestion conditions, digestion solution filtration treatments, we optimized the conditions for extracting and determining hexavalent chromium in soils. The digestion solution was composed of 20 mL of alkaline extract, 100 mg of magnesium chloride, 0.2 mL of dipotassium hydrogen phosphate buffer solution. Microwave digestion was conducted three times. The digested solution was filtrated with medium speed quantitative filter paper, and pH values of the solution were adjusted to 7.0-8.0. Under the optimized conditions, the observed concentrations of certified standard samples of soil were all within the range of standard values, and the recoveries of soil matrix spiked ranged from 85.5% to 88.7%, with the relative standard deviations of 7.6%-8.0%. Compared to the standard method of Alkali Solution Extraction-Flame Atomic Absorption Spectrophotometry (HJ 1082-2019), the method established in this study is suitable for the determination of hexavalent chromium in a large number of soil samples. Microwave digestion technology not only has high extraction efficiency, but also is technically facile and popular in different levels of laboratories. The method of microwave digestion-flame atomic absorption spectrometry proposed in this study will provide technical support for the rapid and accurate determination of hexavalent chromium in soils.