Makris Konstantinos C, Punamiya Pravin, Sarkar Dibyendu, Datta Rupali
Earth and Environmental Science Department, University of Texas at San Antonio, TX, USA.
Analyst. 2008 Feb;133(2):191-6. doi: 10.1039/b714389c. Epub 2007 Dec 20.
A sensitive (method detection limit, 2.0 microg As L(-1)) colorimetric determination of trace As(v) and As(iii) concentrations in the presence of soluble phosphorus (P) concentrations in soil/water extracts is presented. The proposed method modifies the malachite green method (MG) originally developed for P in soil and water. Our method relies upon the finding that As(iii) and As(v) do not develop the green color during P analysis using the MG method. When an optimum concentration of ascorbic acid (AA) is added to a sample containing up to 15 times P > As (microM) concentrations, the final sample absorbance due to P will be equal to that of As(v) molecules. The soluble As concentration can then be quantified by the concentration difference between the mixed oxyanion (As + P) absorbance (proposed method) and the MG method absorbance that measures only P. Our method is miniaturized using a 96-well microplate UV-VIS reader that utilizes minute reagent and sample volumes (120 and 200 microL sample(-1), respectively), thus, minimizing waste and offering flexibility in the field. Our method was tested in a suite of As-contaminated soils that successfully measured both As and P in soil water extracts and total digests. Mean% As recoveries ranged between 84 and 117%, corroborating data obtained with high-resolution inductively-coupled plasma mass-spectrometry. The performance of the proposed colorimetric As method was unaffected by the presence of Cu, Zn, Pb, Ni, Fe, Al, Si, and Cr in both neutral and highly-acidic (ca. pH 2) soil extracts. Data from this study provide the proof of concept towards creating a field-deployable, portable As kit.
本文提出了一种灵敏的比色法（方法检测限为2.0 μg As L⁻¹），用于测定土壤/水提取物中可溶性磷（P）存在时痕量As（Ⅴ）和As（Ⅲ）的浓度。所提出的方法改进了最初用于土壤和水中磷的孔雀石绿方法（MG）。我们的方法基于这样一个发现：在使用MG方法进行磷分析时，As（Ⅲ）和As（Ⅴ）不会产生绿色。当向含有高达15倍P＞As（μM）浓度的样品中加入最佳浓度的抗坏血酸（AA）时，由于磷导致的最终样品吸光度将与As（Ⅴ）分子的吸光度相等。然后，可以通过混合含氧阴离子（As + P）吸光度（所提出的方法）与仅测量P的MG方法吸光度之间的浓度差来定量可溶性As浓度。我们的方法使用96孔微孔板紫外可见分光光度计进行了小型化，该仪器使用的试剂和样品体积很小（分别为120和200 μL样品⁻¹），从而最大限度地减少了浪费并在现场提供了灵活性。我们的方法在一系列受As污染的土壤中进行了测试，成功地测量了土壤水提取物和全消解物中的As和P。平均As回收率在84%至117%之间，与高分辨率电感耦合等离子体质谱法获得的数据一致。所提出的比色As方法的性能不受中性和高酸性（约pH 2）土壤提取物中Cu、Zn、Pb、Ni、Fe、Al、Si和Cr的影响。本研究的数据为创建一种可现场部署的便携式As检测试剂盒提供了概念验证。
