Rosés Martí
Department de Química Analítica, Universitat de Barcelona, Diagonal 647, E-08028 Barcelona, Spain.
J Chromatogr A. 2004 May 28;1037(1-2):283-98. doi: 10.1016/j.chroma.2003.12.063.
The measurement of pH in chromatographic mobile phases has been a constant subject of discussion during many years. The pH of the mobile phase is an important parameter that determines the chromatographic retention of many analytes with acid-base properties. In many instances a proper pH measurement is needed to assure the accuracy of retention-pH relationships or the reproducibility of chromatographic procedures. Three different methods are common in pH measurement of mobile phases: measurement of pH in the aqueous buffer before addition of the organic modifier, measurement of pH in the mobile phase prepared by mixing aqueous buffer and organic modifier after pH calibration with standard solutions prepared in the same mobile phase solvent, and measurement of pH in the mobile phase prepared by mixing aqueous buffer and organic modifier after pH calibration with aqueous standard solutions. This review discusses the different pH measurement and calibration procedures in terms of the theoretical and operational definitions of the different pH scales that can be applied to water-organic solvent mixtures. The advantages and disadvantages of each procedure are also presented through chromatographic examples. Finally, practical recommendations to select the most appropriate pH measurement procedure for particular chromatographic problems are given.
多年来，色谱流动相pH值的测量一直是一个持续讨论的话题。流动相的pH值是一个重要参数，它决定了许多具有酸碱性质的分析物的色谱保留情况。在许多情况下，需要进行适当的pH值测量，以确保保留- pH关系的准确性或色谱分析程序的可重复性。流动相pH值测量通常有三种不同的方法：在添加有机改性剂之前测量水性缓冲液的pH值；在用相同流动相溶剂配制的标准溶液进行pH值校准后，测量混合水性缓冲液和有机改性剂所制备的流动相的pH值；在用水性标准溶液进行pH值校准后，测量混合水性缓冲液和有机改性剂所制备的流动相的pH值。本综述根据可应用于水-有机溶剂混合物的不同pH标度的理论和操作定义，讨论了不同的pH测量和校准程序。还通过色谱实例介绍了每种方法的优缺点。最后，针对特定的色谱问题，给出了选择最合适的pH测量程序的实用建议。
