Dikobe Jerry, Melato Funzani Asnath, Adlem Carel Johannes Lombard, Netshiongolwe Khathutshelo
Tshwane University of Technology, Department of Chemistry, Private Bag X680, Pretoria, 0001, South Africa.
Council for Scientific and Industrial Research, Meiring Naude Road, Brummeria, Pretoria, 0001, South Africa.
Heliyon. 2024 Jul 18;10(14):e34670. doi: 10.1016/j.heliyon.2024.e34670. eCollection 2024 Jul 30.
There is an increasing need for fast and reliable analytical methods for the determination of chemical forms of elements in environmental samples. The interest in chromium is driven by the fact that its toxicity depends on its oxidation state. Although chromium (III) is essential for mammals to maintain their metabolism of proteins, fats, and carbohydrates, chromium (VI) is toxic to humans. For chromium speciation, several costly analytical methods coupling separation methods with atomic absorption and emission spectroscopy have been developed. This article presents the online robotic discrete analyser procedure with the 1,5 diphenylcarbazide (DPC) method for the speciation of Cr (III) and Cr (VI). Cr (III) was determined by difference since it does not interfere with the reaction of Cr (VI)-DPC. Chromium (VI) and total chromium were characterised sequentially (after online oxidation of Cr (III) by Cerium (Ce (IV)). The calibration graphs were linear under experimental conditions up to 1 mg/L Cr (VI) and 2 mg/L total Cr with correlation coefficient R, 0.9997 and 0.9999 respectively. At a signal-to-noise ratio of three, the detection limits were 0.004 mg/L Cr (VI) and 0.015 mg/L total Cr. Good agreement between the real values of certified reference materials and the chromium species content was obtained in this study. The method was precise with a percentage relative standard deviation of less than 2 for hexavalent chromium and total chromium. The t-stat demonstrates that there was no significant difference between the developed robotic discrete analyser method and the ICP-MS method. Except for effluent water, which had recoveries between 65 and 75 % in the assessment of the devised method's selectivity, the overall percentage of recoveries fell between 90 and 110 %, which was generally satisfactory. This method proved to be appropriate for its intended use.
对于测定环境样品中元素的化学形态，人们对快速可靠的分析方法的需求日益增加。对铬的关注源于其毒性取决于氧化态这一事实。虽然铬（III）对哺乳动物维持蛋白质、脂肪和碳水化合物的代谢至关重要，但铬（VI）对人类有毒。对于铬的形态分析，已经开发了几种将分离方法与原子吸收和发射光谱联用的昂贵分析方法。本文介绍了采用1,5 - 二苯卡巴肼（DPC）法对Cr（III）和Cr（VI）进行形态分析的在线机器人离散分析仪程序。由于Cr（III）不干扰Cr（VI） - DPC的反应，因此通过差值法测定Cr（III）。铬（VI）和总铬依次进行测定（在通过铈（Ce（IV））对Cr（III）进行在线氧化之后）。在实验条件下，校准曲线在高达1 mg/L Cr（VI）和2 mg/L总Cr时呈线性，相关系数R分别为0.9997和0.9999。在信噪比为3时，检测限分别为0.004 mg/L Cr（VI）和0.015 mg/L总Cr。在本研究中，认证参考物质的实际值与铬形态含量之间取得了良好的一致性。该方法具有精密度，六价铬和总铬的相对标准偏差百分比均小于2。t检验表明，所开发的机器人离散分析仪方法与电感耦合等离子体质谱法（ICP - MS）之间没有显著差异。在评估所设计方法的选择性时，除了废水的回收率在65%至75%之间外，总体回收率百分比在90%至110%之间，总体上令人满意。该方法证明适用于其预期用途。
