On‐line sample preconcentration technique based on a dynamic pH junction in CE‐amperometric detection for the analysis of biogenic amines in urine

It is difficult to detect biogenic amines (BAs) in biological fluids because of their very low concentrations. In this paper, we reported an on‐line sample preconcentration method in CE‐amperometric detection (CE‐AD) based on a dynamic pH junction, and a concentration enhancement of approximately 100‐fold was achieved compared with the classical CE‐AD methods in the simultaneous analysis of six BAs in urine (dopamine, epinephrine, norepinephrine, tyramine, tryptamine, and serotonin). The technique is proposed based on the sharp pH change generated at the boundary between an acidic sample and the basic BGE zone. Under optimized conditions, all analytes were successfully focused and well separated within 20 min with high efficiency and sensitivity (LODs at S/N = 3 ranging from 5.34 to 68.3 nM). For the analysis of urine samples by this method, satisfactory recoveries were obtained without a complicated pretreatment step or derivatization process. Therefore, it is self‐evident that this approach for the analysis of real biological samples has great potential in the future.