In-channel modification of biosensor electrodes integrated on a polycarbonate microfluidic chip for micro flow-injection amperometric determination of glucose

A microfluidic electrochemical biosensor chip made of full polycarbonate (PC) sheets was fabricated for micro flow-injection amperometric determination of glucose. Microchannel network was embossed onto a PC sheet, and micro gold film electrode bases were prepared on a PC cover sheet with a photo-directed electroless plating technique. After thermal bonding, the integrated gold bases were modified to a glucose oxidase working electrode, an Ag/AgCl reference electrode and a platinum counter electrode, respectively. The sequence of the in-channel modification was studied to avoid the possible contamination of one modified electrode by the reagents used for another electrode. Cooperated with a gravity pump and an automatic sample dispenser, the fabricated micro flow-injection biosensor chip was used for determination of glucose. A detection limit of 4.1 μmol L−1 was achieved at the sampling volume of about 130 nL, and sample throughput rate (or sampling frequency) reached 116 h−1. Inter- and intra-day precisions (RSD) for the determination of a 100 μmol L−1 glucose solution were 0.7% and 1.8%, respectively. Chip-to-chip reproducibility, expressed by the precision of analytical results obtained with individual chips, were less than 10% (RSD). The developed micro flow-injection amperometric biosensor system was successfully applied to the determination of glucose content in pharmaceutical injections.