PDF(Pubmed)
Abstract：
A reliable, rapid, and low-cost procedure for determining very low concentrations of hexavalent chromium (Cr) in water is discussed. The procedure is based in the classical reaction of Cr6+ with diphenylcarbazide. Once this reaction has taken place, sodium dodecylsulfate is added to obtain an ion-pair, and Triton X-114 is incorporated. Next, the heating of the mixture allows two phases that can be separated by centrifugation to be obtained in a cloud point microextraction (CPE) process. The coacervate contains all the Cr6+ originally present in the water sample, so that the measurement by molecular absorption spectrophotometry allows the concentration of the metal to be calculated. No harmful organic solvents are required. The discrimination of hexavalent and trivalent forms is achieved by including an oxidation stage with Ce4+. To take full advantage of the pre-concentration effect inherent to the coacervation process, as well as to minimize reagent consumption and waste generation, a portable mini-spectrophotometer which is compatible with microvolumes of liquid samples is used. The preconcentration factor is 415 and a chromium concentration as low as 0.02 µg L-1 can be detected. The procedure shows a good reproducibility (relative standard deviation close to 3%).
摘要：
一个可靠的，快速,讨论了确定水中非常低的六价铬（Cr）浓度的低成本程序。该程序基于Cr6与二苯基碳酰肼的经典反应。一旦这种反应发生，添加十二烷基硫酸钠以获得离子对，和TritonX-114合并。接下来,混合物的加热允许在浊点微萃取(CPE)过程中获得可通过离心分离的两相。凝聚层含有水样中原来存在的所有Cr6+,以便通过分子吸收分光光度法进行测量可以计算金属的浓度。不需要有害的有机溶剂。六价和三价形式的区分通过包括Ce4+的氧化阶段来实现。为了充分利用凝聚过程固有的预浓缩效应，以及尽量减少试剂消耗和废物产生，使用与微体积液体样品兼容的便携式迷你分光光度计。预浓缩因子为415，可以检测到低至0.02µgL-1的铬浓度。该方法显示出良好的再现性(相对标准偏差接近3%)。
