al-Shawi A W, Dahl R
Research Centre, Norsk Hydro ASA, Porsgrunn, Norway.
J Chromatogr A. 1999 Jul 30;850(1-2):137-41. doi: 10.1016/s0021-9673(99)00543-9.
Chromium(VI) is one of seven elements which is classified in the fertilizer industry as being harmful to plants and biological systems. Phosphate rocks represent the raw material for complex fertilizer production in the world. This paper investigates for the first time the determination of total chromium in phosphate rocks by ion chromatography. The developed analytical method involves the digestion of phosphate rocks with nitric acid followed by sample treatment of the resulting solution. The digestion solution obtained was treated with an oxidising agent (potassium peroxosulphate) to convert all chromium to the hexavalent state. The analytical method developed utilizes anion-exchange ion chromatography to achieve the separation and spectrophotometric post-column reaction for detection with diphenylcarbazide. The relative standard of deviation from analytical data comparison of six different phosphate rocks with atomic absorption spectrometry and inductively coupled plasma atomic emission spectrometry techniques, and cross-analysis data against an internationally certified phosphate rock standard were between 0.58 and 1.45%. Calibration curve between 0.2 and 0.9 microgram/ml was excellent, and the method has a detection limit for Cr(VI) of 0.05 ng. The developed method offers a fast, a reliable and an alternative procedure for the determination of total chromium in phosphate rock deposits by ion chromatography.
六价铬是在肥料工业中被归类为对植物和生物系统有害的七种元素之一。磷矿石是全球复合肥料生产的原材料。本文首次研究了采用离子色谱法测定磷矿石中的总铬。所开发的分析方法包括用硝酸消解磷矿石，然后对所得溶液进行样品处理。将获得的消解溶液用氧化剂（过硫酸钾）处理，以将所有铬转化为六价态。所开发的分析方法利用阴离子交换离子色谱法实现分离，并采用分光光度柱后反应，用二苯卡巴肼进行检测。将六种不同磷矿石的分析数据与原子吸收光谱法和电感耦合等离子体原子发射光谱法技术进行比较，并与国际认证的磷矿石标准进行交叉分析，相对标准偏差在0.58%至1.45%之间。0.2至0.9微克/毫升之间的校准曲线良好，该方法对六价铬的检测限为0.05纳克。所开发的方法为通过离子色谱法测定磷矿床中的总铬提供了一种快速、可靠的替代程序。
