Investigation of matrix effects in capillary zone electrophoresis

The theoretical principles used in the explanation of the separation process in capillary zone electrophoresis (CZE), during the analysis of samples with different matrix cases, are discussed. At the beginning of the CZE separation, an isotachophoretic (ITP) process takes place between the matrix ion and the electrolyte co-ion (ITP range). As a result of the ITP effect, analytes with mobilities between those of the matrix ion and the co-ion, show increasing peak heights with increased matrix concentration whereas for slower or faster analytes peak-broadening occurs. By adding a second matrix ion to the sample, the ITP range can be shifted, so that analyte ions are determined which otherwise could not be analyzed. A further established matrix effect is the shift of the migration times. The reliability of the anticipated effects was investigated for inorganic anions, using several electrolytes and matrix ions.