Verma Devsharan, Verma Santosh Kumar, Deb Manas Kanti
School of Studies in Chemistry, Pt. Ravishankar Shukla University, Raipur, Chhattisgarh 492 010, India.
Talanta. 2009 Apr 15;78(1):270-7. doi: 10.1016/j.talanta.2008.11.020. Epub 2008 Nov 25.
The present paper deals with a new micro-extraction procedure for selective separation of Cr(VI) in the form of a metaloxy anionic species namely dichromate (Cr(2)O(7)(2-)) with N(1)-hydroxy-N(1),N(2)-diphenylbenzamidine (HOA) in to dichloromethane and its subsequent and rapid diffuse reflectance Fourier transform infrared spectroscopic (DRS-FTIR) determination employing potassium bromide matrix. The diffuse reflectance Fourier transform infrared spectroscopy gives both qualitative and quantitative information about the dichromate. The determination of chromium is based on the analytical peak selection, among the various vibrational peaks, at 902 cm(-1). The micro-extraction was based on the liquid-liquid solvent extraction (LLSE) principle. The dichromate binds with the nitrogen and oxygen atoms of N(1)-hydroxy-N(1),N(2)-diphenylbenzamidine (HOA) and forms 1:2, Cr(VI):HOA complex in 0.1 mol L(-1) HCl medium. The formation of above complex, in the acidic medium, is confirmed by the appearance of chocolate-brown color in the micro-extract. The speciation studies of Cr(III) and Cr(VI) is done by conversion of Cr(III) into Cr(VI) utilizing H(2)O(2) as an oxidizing agent. The chemistry of pure dichromate and that of its HOA complex is discussed. The limit of detection (LoD) and the limit of quantification (LoQ) of the method are found to be 0.01 microg g(-1) Cr(2)O(7)(2-) and 0.05 microg g(-1) Cr(2)O(7)(2-), respectively. The standard deviation value and the relative standard value at a level of 10 microg Cr(2)O(7)(2-)/0.1g KBr for n=10 is found to be 0.26 microg Cr(2)O(7)(2-) and 2.6%, respectively. The relative standard deviation (n=8 and 6) for the determination of dichromate (Cr(2)O(7)(2-)) in real human biological fluid samples is observed to be in the range 3.1-7.8%.
本文介绍了一种新的微萃取方法，用于以金属氧阴离子形式选择性分离六价铬，即重铬酸根（Cr₂O₇²⁻），使用N(1)-羟基-N(1),N(2)-二苯基苯甲脒（HOA）将其萃取到二氯甲烷中，并随后采用溴化钾基质进行快速漫反射傅里叶变换红外光谱（DRS-FTIR）测定。漫反射傅里叶变换红外光谱可提供有关重铬酸根的定性和定量信息。铬的测定基于在902 cm⁻¹处的各种振动峰中选择分析峰。微萃取基于液 - 液溶剂萃取（LLSE）原理。在0.1 mol L⁻¹ HCl介质中，重铬酸根与N(1)-羟基-N(1),N(2)-二苯基苯甲脒（HOA）的氮和氧原子结合，形成1:2的Cr(VI):HOA络合物。在酸性介质中上述络合物的形成通过微萃取物中出现巧克力棕色得以证实。利用过氧化氢作为氧化剂将Cr(III)转化为Cr(VI)，对Cr(III)和Cr(VI)进行形态分析研究。讨论了纯重铬酸根及其HOA络合物的化学性质。该方法的检测限（LoD）和定量限（LoQ）分别为0.01 μg g⁻¹ Cr₂O₇²⁻和0.05 μg g⁻¹ Cr₂O₇²⁻。对于n = 10时，在10 μg Cr₂O₇²⁻/0.1 g KBr水平下的标准偏差值和相对标准值分别为0.26 μg Cr₂O₇²⁻和2.6%。在实际人体生物流体样品中测定重铬酸根（Cr₂O₇²⁻）时，相对标准偏差（n = 8和6）在3.1 - 7.8%范围内。
