Parks Jeffrey L, McNeill Laurie, Edwards Marc
Virginia Tech, USA.
Utah State University, USA.
Talanta. 2014 Dec;130:226-32. doi: 10.1016/j.talanta.2014.06.052. Epub 2014 Jun 30.
Three analytical methods were evaluated for hexavalent and trivalent chromium analyses in the presence of natural organic matter (NOM) and alkalinity. Each method was tested using a simulated tap water with 1 μg L(-1) Cr(VI) and 0.8 μg L(-1) Cr(III) and several concentrations of NOM and/or alkalinity. An ion chromatograph with post column reaction cell conforming to USEPA Method 218.7 could accurately quantify Cr(VI) in the presence of up to 8 mg CL(-1) NOM and up to 170 mg L(-1) as CaCO3 alkalinity, and no oxidation of chromium was observed when 0.8 μg L(-1) Cr(III) was also present. A high-performance liquid chromatography coupled with inductively coupled plasma (HPLC-ICPMS) method and a field speciation method were also evaluated. Each of these methods was unaffected by the presence of alkalinity; however, the presence of NOM created issues. For the HPLC-ICPMS method, as the concentration of NOM increased the recovery of Cr(VI) decreased, resulting in a 'false negative' for Cr(VI). However, for the field speciation method, Cr(III) was complexed by NOM and carried through the ion exchange column, resulting in a 'false positive' for Cr(VI).
对三种分析方法进行了评估，用于在天然有机物（NOM）和碱度存在的情况下分析六价铬和三价铬。每种方法都使用含有1 μg L⁻¹ Cr(VI)和0.8 μg L⁻¹ Cr(III)以及几种浓度的NOM和/或碱度的模拟自来水进行测试。配备符合美国环境保护局（USEPA）方法218.7的柱后反应池的离子色谱仪，在存在高达8 mg CL⁻¹ NOM和高达170 mg L⁻¹以碳酸钙计的碱度的情况下，能够准确地定量Cr(VI)，并且当同时存在0.8 μg L⁻¹ Cr(III)时未观察到铬的氧化。还评估了一种高效液相色谱-电感耦合等离子体质谱联用（HPLC-ICPMS）方法和一种现场形态分析方法。这些方法中的每一种都不受碱度存在的影响；然而，NOM的存在产生了问题。对于HPLC-ICPMS方法，随着NOM浓度的增加，Cr(VI)的回收率降低，导致Cr(VI)出现“假阴性”。然而，对于现场形态分析方法，Cr(III)被NOM络合并通过离子交换柱，导致Cr(VI)出现“假阳性”。
