Lin Ma-Yao, Whang Chen-Wen
Department of Chemistry, Tunghai University, Taichung 407, Taiwan.
J Chromatogr A. 2007 Aug 10;1160(1-2):336-9. doi: 10.1016/j.chroma.2007.05.100. Epub 2007 Jun 7.
A rapid and efficient sample preparation method combining microwave-assisted derivatization (MAD) and single-drop microextraction (SDME) for the gas chromatographic (GC) determination of trace Cr(III) in water was developed. Aqueous Cr(III) was first converted to the volatile chromium trifluoroacetylacetonate (Cr(tfa)3) by reaction with 1,1,1-trifluoroacetylacetone (Htfa) under the irradiation of microwave. Derivatization of Cr(III) at ng ml(-1) level could be completed in less than 1 min. The formed Cr(tfa)3 was then extracted into a small droplet (2 microl) of toluene suspended at the tip of a microsyringe needle. The optimal extraction time was 30 min. The solvent drop was directly injected into a GC equipped with a flame photometric detector (FPD) for analysis. The two Cr(tfa)3 isomers extracted could be efficiently separated in 2 min. Linearity (r>0.99) over the concentration range 2-300 ng ml(-1) Cr was obtained and the limit of detection was 0.5 ng ml(-1) Cr. The relative standard deviation was 7.8% at 20 ng ml(-1) Cr (n=5). Applicability of this method to water analysis was examined by analyzing the chromium content in a reference standard water sample and an industrial effluent.
开发了一种快速高效的样品制备方法，该方法结合微波辅助衍生化（MAD）和单滴微萃取（SDME）用于气相色谱（GC）测定水中痕量Cr（III）。首先在微波辐射下，通过与1,1,1-三氟乙酰丙酮（Htfa）反应，将水溶液中的Cr（III）转化为挥发性的三氟乙酰丙酮铬（Cr（tfa）3）。Cr（III）在ng ml(-1)水平的衍生化可在不到1分钟内完成。然后将形成的Cr（tfa）3萃取到悬浮在微量注射器针头尖端的一小滴（2微升）甲苯中。最佳萃取时间为30分钟。将溶剂滴直接注入配备火焰光度检测器（FPD）的GC中进行分析。萃取得到的两种Cr（tfa）3异构体可在2分钟内有效分离。在2-300 ng ml(-1) Cr浓度范围内获得线性关系（r>0.99），检测限为0.5 ng ml(-1) Cr。在20 ng ml(-1) Cr（n=5）时相对标准偏差为7.8%。通过分析参考标准水样和工业废水中的铬含量，检验了该方法在水分析中的适用性。
