A sensitive capillary zone electrophoresis (CZE) combined with field-amplified sample injection (FASI) method was investigated to simultaneously determine diltiazem (DI) hydrochloride and metoprolol (ME) tartrate in human serum. This method was validated by linearity, limits of detection (LOD), stability, precision and accuracy, and the related parameters are linearity (r2 > 0.9980), intra- and inter-day precisions (intra-day relative standard deviation (RSD) is 2.3-3.4%, and inter-day RSD is 3.8-7.5%) and the LOD (0.02 ng/mL for ME tartrate and 0.01 ng/mL for DI hydrochloride). So the proposed method is rapid, sensitive and accurate for determination of these two anti-anginal drugs in human serum. As for enrichment conditions, it was helpful to add phosphoric acid and isopropanol into samples for enrichment efficiency. A model was established to illustrate the possible enrichment mechanism of analytes, and a theory of half-width was also applied in CZE combined with FASI method to evaluate the peak performance.
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