Research Group of PGM Chemistry, Department of Chemistry and Polymer Science, Stellenbosch University, Private Bag XI, Stellenbosch 7602, Western Cape, South Africa.
Talanta. 2010 Jun 30;82(1):348-58. doi: 10.1016/j.talanta.2010.04.049. Epub 2010 May 15.
A hyphenated ion-pair (tetrabutylammonium chloride-TBACl) reversed phase (C(18)) HPLC-ICP-MS method (High Performance Liquid Chromatography Inductively Coupled Plasma Mass Spectroscopy) for anionic Rh(III) aqua chlorido-complexes present in an HCl matrix has been developed. Under optimum chromatographic conditions it was possible to separate and quantify cationic Rh(III) complexes (eluted as a single band), [RhCl(3)(H(2)O)(3)], cis-RhCl(4)(H(2)O)(2), trans-RhCl(4)(H(2)O)(2) and RhCl(n)(H(2)O)(6-n) (n=5, 6) species. The RhCl(n)(H(2)O)(6-n) (n=5, 6) complex anions eluted as a single band due to the relatively fast aquation of RhCl(6) in a 0.1 mol L(-1) TBACl ionic strength mobile phase matrix. Moreover, the calculated t(1/2) of 1.3 min for RhCl(6) aquation at 0.1 mol kg(-1) HCl ionic strength is significantly lower than the reported t(1/2) of 6.3 min at 4.0 mol kg(-1) HClO(4) ionic strength. Ionic strength or the activity of water in this context is a key parameter that determines whether RhCl(n)(H(2)O)(6-n) (n=5, 6) species can be chromatographically separated. In addition, aquation/anation rate constants were determined for RhCl(n)(H(2)O)(6-n) (n=3-6) complexes at low ionic strength (0.1 mol kg(-1) HCl) by means of spectrophotometry and independently with the developed ion-pair HPLC-ICP-MS technique for species assignment validation. The Rh(III) samples that was equilibrated in differing HCl concentrations for 2.8 years at 298K was analyzed with the ion-pair HPLC method. This analysis yielded a partial Rh(III) aqua chlorido-complex species distribution diagram as a function of HCl concentration. For the first time the distribution of the cis- and trans-RhCl(4)(H(2)O)(2) stereoisomers have been obtained. Furthermore, it was found that relatively large amounts of 'highly' aquated RhCl(n)(H(2)O)(6-n) (n=0-4) species persist in up to 2.8 mol L(-1) HCl and in 1.0 mol L(-1) HCl the abundance of the RhCl(5)(H(2)O) species is only 8-10% of the total, far from the 70-80% as previously proposed. A 95% abundance of the RhCl(6) complex anion occurs only when the HCl concentration is above 6 mol L(-1). The detection limit for a Rh(III) species eluted from the column is below 0.147 mg L(-1).
一种由四丁基氯化铵-氯化钛（TBACl）反相（C（18））高效液相色谱-电感耦合等离子体质谱法（高效液相色谱-电感耦合等离子体质谱）已被开发用于分析存在于 HCl 基质中的阴离子 Rh（III）水合氯配合物。在最佳色谱条件下，可以分离和定量阳离子 Rh（III）配合物（作为单个带洗脱），[RhCl（3）（H（2）O）（3）]，顺式-[RhCl（4）（H（2）O）（2）]-，反式-[RhCl（4）（H（2）O）（2）]-和[RhCl（n）（H（2）O）（6-n）]（3-n）（n=5，6）物种。[RhCl（n）（H（2）O）（6-n）]（3-n）（n=5，6）配合物阴离子由于在 0.1 mol L（-1）TBACl 离子强度流动相基质中相对较快的[RhCl（6）]（3-）水合作用而作为单个带洗脱。此外，在 0.1 mol kg（-1）HCl 离子强度下，[RhCl（6）]（3-）水合作用的计算半衰期 t（1/2）为 1.3 分钟，显著低于在 4.0 mol kg（-1）HClO4 离子强度下报道的 6.3 分钟半衰期。在这种情况下，离子强度或水的活度是决定[RhCl（n）（H（2）O）（6-n）]（3-n）（n=5，6）物种是否可以进行色谱分离的关键参数。此外，通过分光光度法和开发的离子对 HPLC-ICP-MS 技术分别测定了[RhCl（n）（H（2）O）（6-n）]（3-n）（n=3-6）配合物在低离子强度（0.1 mol kg（-1）HCl）下的水合/配体交换速率常数，用于验证物种归属。用离子对 HPLC 方法分析了在 298K 下在不同 HCl 浓度下平衡 2.8 年的 Rh（III）样品。该分析提供了 HCl 浓度的 Rh（III）水合氯配合物物种分布图。首次获得了顺式和反式-[RhCl（4）（H（2）O）（2）]（-）立体异构体的分布。此外，发现相对大量的“高度”水合[RhCl（n）（H（2）O）（6-n）]（3-n）（n=0-4）物种在高达 2.8 mol L（-1）HCl 中以及在 1.0 mol L（-1）HCl 中仍然存在，[RhCl（5）（H（2）O）]（2-）物种的丰度仅为总丰度的 8-10%，远低于先前提出的 70-80%。当 HCl 浓度高于 6 mol L（-1）时，[RhCl（6）]（3-）配合物阴离子的丰度达到 95%。从柱上洗脱的 Rh（III）物种的检测限低于 0.147 mg L（-1）。
