松香试样的预处理及痕量砷的测定方法研究

Study on Pretreatment of Rosin Sample and Determination of Trace Arsenic in the Rosin

提出松香样品添加混合助剂MgCO3 +Mg(NO3 ) 2 进行干灰化预处理 ,并将此法与硝酸 +高氯酸的湿消解法和仅添加Mg(NO3 ) 2 的干灰化法进行了比较。结果表明 ,本法在抑制砷的挥发方面 ,比仅用Mg(NO3 ) 2作为灰化助剂的干灰化法效果更好 ,砷的回收率在 94 %～ 10 5 % ;比用硝酸 +高氯酸湿消解法分解试样更彻底 ,可以避免剩余酸除去时引起的砷损失。试验还表明 ,HG AFS测As的检出限DL =0 31ng·mL-1,松香中的砷不用富集便可进行测量 ,对国家标准物质桃叶GBW 0 85 0 1中砷的测定结果与推荐值一致 ,方法的相对标准偏差RSD =2 6 %～ 4 4 %。

In order to restrain the volatilizatilon of trace arsenic in rosin samples during the pretreatment procedure, a dry ashing method of adding compound auxiliary ashing agent was introduced in this paper. The procedure involved mixing 5 g rosin powder with 1 g MgCO3 powder and 5 mL 50% (W/W) Mg(NO3)(2) solution in the porcelain crucible, drying the mixture under 60degreesC, and then ashing it at 500degreesC. The experimental result showed that with this method the recovery for trace arsenic was 94%-105%, which was higher than the dry ashing method that adds only Mg(NO3)(2) as an auxiliary ashing agent. On the other hand, the rosin samples were decomposed more completely by the proposed method than by HNO3 + HClO4 wet ashing. The experiment showed that the detection limit of arsenic with hydride generation atomic fluorescence spectrometry was 0.31 ng(.)mL(-1), so there was no need to enrich arsenic from the rosin before test. The arsenic in the standard reference substance peach leaf (GBW08571) was determined by the method. The results were in good agreement with certified values. The relative standard deviation was between 2.6%-4.4%.