Sensitive Determination of Arsenic and Selenium in steels by High Power Nitrogen Microwave Induced Plasma Atomic Emission Spectrometry Coupled with Hydride Generation Technique

摘要

An annular-shaped high power nitrogen microwave inducedplasma(N2-MIP) produced at atmospheric pressure by an Okamotocavity in a surface wave mode has been used as a new and efficientexcitation source for atomic emission spectrometry(AES).Theresults show that this kind of MIP source is more stable thanconventional low power MIPs and remarkably tolerant to directand continuous introduction of wet aerosols and molecular gasessuch as hydrogen,oxygen, air and gaseous hydrides because of itshigh input microwave power.Under the optimized experimentalconditions,the best attainable detection limits at As(I)228.812 and Se(I) 196.026 nm by use of N2-MIP-AES coupled withhydride generation technique were 2.99ng As/ml and 0.86 ng Se/mlwith a linear dynamic ranges of 5 to 10,000 ng As/ml and 1 to5,000ng Se/ml.The presence of several diverse elements has beenfound to cause more or less a depressing interference with thedetermination of arsenic and selenium by the present technique.Of the several pre-reductants potassium iodide has been foundto be the most prefer-able to reduce As(V) to As(III) prior tohydride generation for the determination of totalarsenic,i.e.,As(III)+As(V).To the contrary,the heating ofsample solutions,previously acidified in 5 M with hydrochloricacid,at 80℃ for 20 min was the best way to pre-reduce Se(VI)to Se(IV) before hydride generation for the determination oftotal selenium,i.e.,Se(IV)+Se(VI).The proposed method wasapplied to the determination of low concentrations of arsenicand selenium in carbon steels and stainlesssteels,respectively.The results obtained by this method were ingood agreement with the certified values.