Pires Cherrine K, Reis Boaventura F, Morales-Rubio Angel, de la Guardia Miguel
Department of Analytical Chemistry, University of Valencia, 50 Dr. Moliner Street, 46100 Burjassot Valencia, Spain.
Talanta. 2007 Jun 15;72(4):1370-7. doi: 10.1016/j.talanta.2007.01.044. Epub 2007 Jan 30.
A simple and sensitive multicommutated flow procedure, implemented by employing a homemade light emitting diode (LED) based photometer, has been developed for the determination of chromium (VI) and total chromium in water. The flow system comprised a set of four solenoid micro-pumps, which were assembled to work as fluid propelling and as commutating devices. The core of the detection unit comprised a green LED source, a photodiode and a homemade flow cell of 100mm length and 2mm inner diameter. The photometric procedure for the speciation of chromium in natural waters was based on the reaction of Cr (VI) with 1,5-diphenylcarbazide. Cr (III) was previously oxidized to Cr (VI) and determined as the difference between total Cr and Cr (VI). After carrying out the assays to select the best operational conditions the features of the method included: a linear response ranging from 10 to 200mugl(-1) Cr (III) and Cr (VI) (r=0.999, n=7); limits of detection of 2.05 and 1.0mugl(-1) for Cr (III) and Cr (VI), respectively; a relative standard deviation lower than 2.0% (n=20) for a typical solution containing 50mugl(-1) Cr; a sampling throughput of 67 and 105 determinations per hour for total Cr and Cr (VI), respectively, and recovery values within the range of 93-108% for spiked concentrations of the order of 50mugl(-1).
采用自制的基于发光二极管（LED）的光度计，开发了一种简单且灵敏的多通道流动分析方法，用于测定水中的六价铬和总铬。流动系统由一组四个螺线管微型泵组成，这些泵组装在一起用作流体推进和换向装置。检测单元的核心包括一个绿色LED光源、一个光电二极管和一个自制的长度为100mm、内径为2mm的流通池。天然水中铬形态分析的光度法基于六价铬与1,5-二苯基卡巴肼的反应。三价铬预先氧化为六价铬，并通过总铬与六价铬的差值来测定。在进行实验以选择最佳操作条件后，该方法的特点包括：三价铬和六价铬的线性响应范围为10至200μg l⁻¹（r = 0.999，n = 7）；三价铬和六价铬的检测限分别为2.05和1.0μg l⁻¹；对于含50μg l⁻¹铬的典型溶液，相对标准偏差低于2.0%（n = 20）；总铬和六价铬的采样通量分别为每小时67次和105次测定，对于浓度约为50μg l⁻¹的加标浓度，回收率在93 - 108%范围内。
