Electrophoretic analysis of food dyes using a miniaturized microfluidic system

A simple and sensitive on-chip preconcentration, separation, and electrochemical detection (ED) method for the electrophoretic analysis of food dyes was developed. The microchip comprised of three parallel channels: the first two are for the field-amplified sample stacking (FASS) and subsequent field-amplified sample injection (FASI) steps, while the third one is for the micellar EKC with ED (MEKC-ED) step. The food dyes were initially extracted from real samples by employing a method that was simpler, easier, and faster compared with a standard method. The extraction of the samples was characterized by UV-Vis and electrochemical experiments. The chronoamperometric detection was performed with a glassy carbon electrode coupled horizontally with the microchip at the separation channel exit. Experimental parameters affecting the analytical performance of the method were assessed and optimized. The sensitivity of the method was improved by approximately 10,800-fold when compared with a conventional MEKC-ED analysis. Reproducible response was observed during multiple injections of samples with an RSD of <7.2% (n=5). The calibration plots were linear (r2=0.998) within the range of 1.0 nM-1.0 microM for all food dyes. LODs were estimated between 1.0 and 5.0 nM, based on S/N=3, for food dyes. The applicability of the method for the analysis of food dyes in real sample was demonstrated.