石墨炉原子吸收光谱法测定地球化学样品中微量铬

摘要

应用ZEEnit 600型石墨炉原子吸收分光光度计测定地球化学样品中微量铬.在分解样品过程中,加入高氯酸,使Cr(Ⅱ)、Cr(Ⅲ)同时被氧化为Cr(Ⅵ),避免了Cr(Ⅲ)和Cr(Ⅵ)的吸光度不同而造成的分析误差.采用最大功率升温和纵向加热石墨管技术,测定铬的原子化温度降低至2100℃,以抗坏血酸作基体改进剂,测定灵敏度得到提高,改善了方法精密度,并且延长了石墨管的使用寿命.采用交流塞曼扣背景测量技术,方法的线性范围为0～200ng/mL,相关系数为0.9980;铬的检出限降低至0.05μg/g(稀释因子为2500),方法精密度(RSD)为2.11%～5.96%.经国家一级地球化学标准物质验证,测定值与标准值吻合,结果准确可靠.%This article described the application of the ZEEnit 600 graphite furnace atomic absorption spectrophotometer on determination of trace chromium in geochemical samples. The HClO4 was added during digestion to oxidize both Cr( Ⅱ ) and Cr( Ⅲ) to Cr(Ⅳ) , which avoid the analysis error caused by the different absorbencies of Cr( Ⅱ ) and Cr(Ⅲ ). The atomization temperature of Cr was reduced to 2100 ℃ by the technique of longitudinal heating at maximum speed in graphite furnace. The addition of ascorbic acid as matrix modifier improved the sensitivity and precision of the measurement, meanwhile increased the service life of graphite furnace. The linear range is from 0 to 200 ng/mL and the correlation coefficient is 0.9980 with background correction by using inverse Zeeman effect. The detection limits of the method is 0.05 μg/g (dilution factor is 2500) , the precision of the method (RSD) is 2.11％ -5.96％. The method has been validated by the national standard materials. The measured results were consistent with the certified values, and the results were accurate and reliable.