野外现场多元素快速分析方法的研究和应用 Ⅱ铜铁锌的测定

Methods for Rapid Multielement Analysis in the Field and Their ApplicationⅡ.Determination of Copper, Iron and Zinc

针对野外现场分析的要求,选择了微珠比色、微量滴定和蛋膜富集比色三项技术,拟定了30个痕量(或次量、主量)元素的40个分析方法;对方法的准确性、精密度、灵敏度等参数与公认可靠方法进行了对比,或采用标准物质分析进行验证;在方法拟定过程中特别注意了快速方便、降低环境污染、降低成本和提高方法的可操作性。这些方法对实验环境条件要求不高,满足野外现场分析应用。微珠比色法测铜以浴铜灵为显色剂,可不经分离测出各种样品中痕量铜,摩尔吸光系数1×104L·mol-1·cm-1,检出限为5ng,加标回收率为95%～105%,RSD(n=20)为2.2%。微珠比色法测铁以向红菲口罗啉为显色剂,铜干扰测定,可加入Na2S2O3掩蔽,摩尔吸光系数为1×105L·mol-1·cm-1,RSD(n=21)为3.4%,方法适用于测定0.001μg/g以上的Fe,测试结果与其它方法相吻合。微珠比色法测锌以吡啶偶氮萘酚为显色剂,一般矿样、水样、生物样品可直接测定,Cd、Ni、Cu等金属元素含量高时,可利用DDTC-CHCl3小体积萃取法分离锌,检出限1ng,RSD(n=20)为6.9%,用于铅锌矿等国家一级标准物质中锌的测定,结果与标准值相符。

In allusion to the need of elemental analysis in the field, three techniques of microbead colorimetry, microtitrimetry and eggshell membrane enrichment colorimetry have been established and forty analytical methods for thirty elements based on these three techniques were studied. Accuracy, precision and sensitivity provided by these methods were compared with other commonly used methods or tested by standard reference material analysis. Special attention was paid to the aspects of effectiveness, convenience, environmental pollution and operation cost of the methods. The results from the study show that these methods provide many advantages and can be used in elemental analysis in fieldwork. In this paper, three microbead colorimetric methods for determinations of copper, iron and zinc have been developed respectively. Copper is determined using 2,9,methyl4,7phenyl1,10phenanthroline as chromagenic reagent without any interferent separation step. The apparent molar absorptivity is 1×104 L·mol-1·cm-1 with detection limit of 5 ng for Cu. The recovery of standard addition for Cu is 95%～105% with precision of 2.2% RSD (n=20). Iron is determined using 4,7phenyl1,10phenanthroline as chromagenic reagent with Na2S2O3 as a masking reagent for eliminating the interference from Cu. The apparent molar absorptivity is 1×105 L·mol-1·cm-1 with detection limit of 0.001 μg/g for Fe. The method has been applied to the determination of Fe in geological samples. The results are in agreement with those provided by other method with precision of 3.4% RSD (n=21). Zinc is determined using pyridylazonaphthol as chromagenic reagent with detection limit of 1 ng. The step of extraction separation of Zn with DDTCCHCl3 should be taken when coexisting ions of Cd, Ni and Cu are in high levels in samples. The method has been applied to the determination of Zn in geological standard samples. The results are in agreement with the certified values with precision of 6.9% RSD (n=20).