Kolliopoulos Athanasios V, Kampouris Dimitrios K, Banks Craig E
Faculty of Science and Engineering, School of Chemistry and the Environment, Division of Chemistry and Environmental Science, Manchester Metropolitan University, Chester Street, Manchester M1 5GD, Lancs, U.K.
Anal Chem. 2015 Apr 21;87(8):4269-74. doi: 10.1021/ac504602a. Epub 2015 Apr 9.
Phosphorus is one of the key indicators of eutrophication levels in natural waters where it exists mainly as dissolved phosphorus. Various analytical protocols exist to provide an offsite analysis, and a point of site analysis is required. The current standard method recommended by the Environmental Protection Agency (EPA) for the detection of total phosphorus is colorimetric and based upon the color of a phosphomolybdate complex formed as a result of the reaction between orthophosphates and molybdates ions where ascorbic acid and antimony potassium tartrate are added and serve as reducing agents. Prior to the measurements, all forms of phosphorus are converted into orthophosphates via sample digestion (heating and acidifying). The work presented here details an electrochemical adaptation of this EPA recommended colorimetric approach for the measurement of dissolved phosphorus in water samples using screen-printed graphite macroelectrodes for the first time. This novel indirect electrochemical sensing protocol allows the determination of orthophosphates over the range from 0.5 to 20 μg L(-1) in ideal pH 1 solutions utilizing cyclic voltammetry with a limit of detection (3σ) found to correspond to 0.3 μg L(-1) of phosphorus. The reaction time and influence of foreign ions (potential interferents) upon this electroanalytical protocol was also investigated, where it was found that a reaction time of 5 min, which is essential in the standard colorimetric approach, is not required in the new proposed electrochemically adapted protocol. The proposed electrochemical method was independently validated through the quantification of orthophosphates and total dissolved phosphorus in polluted water samples (canal water samples) with ion chromatography and ICP-OES, respectively. This novel electrochemical protocol exhibits advantages over the established EPA recommended colorimetric determination for total phosphorus with lower detection limits and shorter experimental times. Additionally this electrochemical adaptation allows the determination of dissolved phosphorus without the use of ascorbic acid and antimony potassium tartrate as reducing agents (as used in the colorimetric method). The potential portability of this protocol is demonstrated in the development of the PhosQuant electrochemical device and provides a portable device for the rapid electrochemical detection of dissolved phosphorus using screen-printed electrodes.
磷是天然水体富营养化水平的关键指标之一，在天然水体中它主要以溶解态磷的形式存在。有多种分析方法可用于进行异地分析，但仍需要现场分析。美国环境保护局（EPA）推荐的用于检测总磷的现行标准方法是比色法，该方法基于正磷酸盐与钼酸根离子反应形成的磷钼酸盐络合物的颜色，其中添加了抗坏血酸和酒石酸锑钾作为还原剂。在测量之前，通过样品消解（加热和酸化）将所有形式的磷转化为正磷酸盐。本文首次详细介绍了对这种EPA推荐的比色法进行电化学改进，以使用丝网印刷石墨宏观电极测量水样中的溶解磷。这种新颖的间接电化学传感方法能够在理想的pH 1溶液中，利用循环伏安法测定0.5至20 μg L⁻¹范围内的正磷酸盐，检测限（3σ）为0.3 μg L⁻¹的磷。还研究了反应时间以及外来离子（潜在干扰物）对该电分析方法的影响，结果发现，在新提出的电化学改进方法中，标准比色法中必不可少的5分钟反应时间并非必需。通过分别使用离子色谱法和电感耦合等离子体发射光谱法（ICP - OES）对污染水样（运河水样）中的正磷酸盐和总溶解磷进行定量分析，独立验证了所提出的电化学方法。这种新颖的电化学方法相对于既定的EPA推荐的总磷比色测定法具有优势，检测限更低且实验时间更短。此外，这种电化学改进方法无需使用抗坏血酸和酒石酸锑钾作为还原剂（比色法中使用）即可测定溶解磷。PhosQuant电化学装置的开发证明了该方法具有潜在的便携性，提供了一种使用丝网印刷电极快速电化学检测溶解磷的便携式装置。
