Dual fluorescence and electrochemical detection on an electrophoresis microchip

Simultaneous amperometric and fluorescence detection in a microfabricated electrophoresis chip is reported. Detection limits of 448 nM and 1.52, 16, and 28 microM have been achieved for dopamine, catechol, NBD-arginine, and NBD-phenylalanine, respectively. These two orthogonal detection schemes allow analysis of a wider spectrum of compounds per separation, leading to higher throughput and enabling resolution of two neutral analytes, NBD-arginine and catechol. In addition, insight into the detection and separation mechanisms is realized. Differences in migration time and peak widths between the two detectors are compared, providing a better understanding of detector alignment. A common problem encountered in electrophoresis is run-to-run migration time irreproducibility for certain samples. This novel microchip dual detection system has been utilized to reduce this irreproducibility. An unknown sample is monitored with one detector while a standard (i.e., ladder) is added to the sample and monitored simultaneously with the other detector. This dual detection method is demonstrated to normalize unknown peak mobilities in a cerebral spinal fluid sample.