Analysis of anions in aqueous samples by ion chromatography and capillary electrophoresis. A comparative study of peak modeling and validation criteria

The object of this study is the comparison of two methods for the quantitative analysis of anions in aqueous samples: ion chromatography with conductimetric detection, and capillary zone electrophoresis with indirect photometric detection. The comparison includes modeling of experimental peaks as well as statistical validation criteria according to the recommendations of the International Conference on Harmonisation. In ion chromatography, peak shapes are Gaussian or exponentially modified Gaussian, and the number of theoretical plates calculated using the appropriate mathematical relations correspond well to those obtained from statistical moments. Peaks in capillary electrophoresis, however, do not follow the same models. A different model, treating the peaks as right angle triangles, has been studied. Equations corresponding to this model permit a good estimation of plate numbers. The statistical validation of these methods includes detection limits, linearity, accuracy and precision. Overall, ion chromatography yields better validation results than capillary electrophoresis. In the latter method the injection mode plays an important role, with voltage injection giving lower detection limits than hydrodynamic injection.