微波辅助电感耦合等离子体光谱法进行RoHS限定的重金属检测

Determination of Heavy Metals for RoHS Compliance by ICP-OES Spectrometry Coupled with Microwave Extraction System

电子电气产品中有害金属已经引起了人们高度关注。针对RoHS指令的巨大压力,文章展示了微波消解制样,ICP-OES(电感耦合等离子体发射光谱法)测定电气电子产品中Cr,Hg,Pb,Cd的痕量浓度的整个过程,并对该法的精确度、回复率、重现性和干扰问题做了讨论。研究表明,微波消解较之传统制样方法可更快速、无损失、无污染的制备试样。通过对整个工作日不同时间内和不同波长处四种重金属回复率分析,85%～115%的精度范围说明微波消解制样、试样介入系统及ICP检测过程损失和污染较小。重现率实验表明在工作时间内ICP具有较好的稳定性及材质效应较小。采用标准添加技术或内元素校正法可以有效克服Ni,As,Fe等对Cd的干扰,从而解决了原子吸收光谱法分析中棘手的难题。对于背景线漂移或光谱交叠问题采用多波长同时选择和两纠正点方法得以很好地解决。同时,样品、标准溶液和标准添加溶液中的痕量重金属元素分析可达到较小的相对标准偏差(<3%)和较低检出限(3σ<1μg.L-1,n=5),这些说明ICP-OES具有高精度和高可靠性。这为要求符合欧盟环保指令限定范围的电子电气业提供了较好的技术支持。

The harm of heavy metals contained in electronic and electrical equipment（EEE） on environment is of high concern by human.Aiming to handle the great challenge of RoHS compliance,the determinations of trace or ultratrace chromium（Cr）,cadmium（Cd）,mercury（Hg） and lead（Pb） by inductively coupled plasma optical emission spectrometry（ICP-OES） was performed in the present paper,wherein,microwave extraction technology was used to prepare the sample solutions.In addition,the precision,recovery,repeatability and interference issues of this method were also discussed.The results exhibited that using the microwave extraction system to prepare samples is more quick,lossless,contamination-free in comparison with the conventional extraction methods such as dry ashing,wet-oven extraction etc.By analyzing the recoveries of these four heavy metals over different working time and wavelengths,the good recovery range between 85% and 115% showed that there was only tiny loss or contamination during the process of microwave extraction,sample introduction and ICP detection.Repeatability experiments proved that ICP plasma had a good stability during the working time and the matrix effect was small.Interference was a problem troublesome for atomic absorption spectrometry（AAS）,however,the techniques of standard additions or inter-element correction（IEC） method can effectively eliminated the interferences of Ni,As,Fe etc.with the Cd determination.By employing the multi-wavelengths and two correction point methods,the issues of background curve sloping shift and spectra overlap were successfully overcome.Besides,for the determinations of trace heavy metal elements,the relative standard deviation（RSD） was less than 3% and the detection limits were less than 1 μg·L-1（3σ,n=5）for samples,standard solutions,and standard additions,which proved that ICP-OES has a good precision and high reliability.This provided a reliable technique support for electronic and electrical（EE） industries to comply with RoHS directive.