Ashitomi Masaki, Yoshimura Kazuhisa
Department of Chemistry, Faculty of Sciences, Kyushu University, Hakozaki, Higashi, Fukuoka 812-8581, Japan.
Anal Sci. 2013;29(8):823-9. doi: 10.2116/analsci.29.823.
A cation-exchange column (TSK IC-Cation, 4.6 mm i.d., 10 mm) was used as a reaction/concentration/separation medium in an HPLC system. Cr(VI) and 1,5-diphenylcarbazide (DPC) were on-line mixed and reacted in a flow tube. When the reagents flowed into the column, both DPC and the complex were concentrated on the column, and the higher DPC concentration accelerated the remaining Cr(VI) to quickly complete the reaction with the DPC on the column. After the complexation and preconcentration, the complex and the extra DPC were eluted by a mixed solution containing lanthanum chloride and 1-propanol. The absorbance of the Cr(III)-DPCO complex at 540 nm was continuously monitored. In addition, the dissolved Cr(III) could be oxidized to Cr(VI) by 185-nm irradiation using a low pressure ultraviolet (UV) lamp for 8 min, and then analyzed by the present method as total chromium, thus the quantitative speciation analysis of Cr(III) and Cr(VI) was realized. In the range of 1 ng dm⁻³ - 100 μg dm⁻³ Cr(VI) concentration, the calibration curve was linear. The analytical time was 8 min for Cr(VI) and 24 min for total Cr. The detection limit (3σ) of the method was 0.6 ng dm⁻³ for Cr(VI) and 0.8 ng dm⁻³ for total chromium when using a 3.9-cm³ water sample. The present method could be successfully applied to the speciation analysis of dissolved chromium in natural water, and the leaching test of Cr(III) and Cr(VI) from stainless steel.
在高效液相色谱系统中，使用阳离子交换柱（TSK IC - Cation，内径4.6 mm，长10 mm）作为反应/浓缩/分离介质。六价铬（Cr(VI)）和1,5 - 二苯卡巴肼（DPC）在流动管中在线混合并反应。当试剂流入柱子时，DPC和络合物都在柱上浓缩，较高的DPC浓度加速了剩余的Cr(VI)与柱上的DPC快速完成反应。络合和预浓缩后，络合物和过量的DPC用含有氯化镧和1 - 丙醇的混合溶液洗脱。连续监测Cr(III) - DPCO络合物在540 nm处的吸光度。此外，溶解的Cr(III)可以用低压紫外（UV）灯在185 nm照射8分钟氧化为Cr(VI)，然后用本方法作为总铬进行分析，从而实现了Cr(III)和Cr(VI)的定量形态分析。在1 ng dm⁻³ - 100 μg dm⁻³的Cr(VI)浓度范围内，校准曲线呈线性。Cr(VI)的分析时间为8分钟，总铬的分析时间为24分钟。当使用3.9 cm³水样时，该方法对Cr(VI)的检测限（3σ）为0.6 ng dm⁻³，对总铬的检测限为0.8 ng dm⁻³。本方法可成功应用于天然水中溶解铬的形态分析以及不锈钢中Cr(III)和Cr(VI)的浸出试验。
