Analytical and Environmental Chemistry Section, New South Wales Environment Protection Authority, PO Box 29, Lidcombe, NSW 1825, Australia.
Talanta. 2002 Jul 19;57(6):1143-53. doi: 10.1016/s0039-9140(02)00196-0.
A new method for determining ultra-trace levels of hexavalent chromium in ambient air has been developed. The method involves a 24-h sampling of air into potassium hydroxide solution, followed by silica gel column separation of chromium (VI), then preconcentration by complexation and solvent extraction. The chromium (VI) complex was dissolved in nitric acid. The resultant chromium ions were determined by inductively coupled plasma mass spectrometry (ICP-MS) using a dynamic reaction cell (DRC) with ammonia as the reactive gas to reduce polyatomic interferences. The interconversion of chromium in potassium hydroxide solution and air sample matrix were investigated under ambient conditions. It was found that there was no conversion of chromium (VI) into chromium (III) species. However, it was observed that some chromium (III) species were converted into chromium (VI) species. For a KOH solution containing 100 mug l(-1) of chromium (III) species, the rate of conversion was found to be 3% after 24 h exposure, 8% after 48 h, 10% after 72 h and no further conversion was observed thereafter. However, in a solution containing air sample matrix, 9.3% of chromium (III) converted to chromium (VI) within 6 h, and during the course of a 11-day exposure period, 13% (range 8-17%) of chromium (III) converted to chromium (VI). The method detection limit (MDL) for chromium (VI) in potassium hydroxide solution (0.025 M) was found to be 2x10(-2) mug l(-1). This is equivalent to 0.2 ng m(-3) (for 23 m(3) air sampled into 200 ml of KOH solution over a 24-h period). The recovery of spiked chromium (VI) from solutions containing air sample matrix was 95+/-9% (n=8). Matrix related interferences were estimated to be less than 10% based on recovery studies. The concentration of airborne chromium (VI) in Sydney residential areas was found to be less than 0.2 ng m(-3), however, in industrial areas the concentrations ranged from 0.2 to 1.3 ng m(-3) using this analytical procedure.
一种测定环境空气中六价铬的新方法已经建立。该方法包括将空气在氢氧化钾溶液中进行 24 小时采样，然后用硅胶柱分离六价铬，再通过络合和溶剂萃取进行预浓缩。六价铬络合物用硝酸溶解。用带有氨作为反应气体的动态反应池（DRC）的电感耦合等离子体质谱法（ICP-MS）测定生成的铬离子。在环境条件下研究了氢氧化钾溶液和空气样品基质中铬的相互转化。结果表明，没有将六价铬转化为三价铬。但是，观察到一些三价铬物种转化为六价铬物种。对于含有 100 µg l(-1) 三价铬物种的 KOH 溶液，在 24 小时暴露后，发现转化率为 3%，48 小时后为 8%，72 小时后为 10%，此后没有进一步转化。然而，在含有空气样品基质的溶液中，6 小时内有 9.3%的三价铬转化为六价铬，在 11 天的暴露期间，有 13%（8-17%）的三价铬转化为六价铬。在 0.025 M 氢氧化钾溶液中，六价铬的方法检测限（MDL）为 2x10(-2) µg l(-1)。这相当于在 24 小时内用 200 毫升 KOH 溶液采集 23 立方米空气时，空气中六价铬的浓度为 0.2 ng m(-3)（空气中六价铬的浓度小于 0.2 ng m(-3)，然而，在工业区，使用这种分析方法，浓度范围为 0.2 至 1.3 ng m(-3)。
