A fast and reliable route integrating calibration and analysis protocols for water-soluble vitamin determination on microchip-electrochemistry platforms

A novel analytical route to determine water-soluble vitamins (B group and C) using single channel microchip-electrochemistry platforms is presented. The electrochemical detection protocol was carefully optimized, and it was shown that it was crucial to use 1 M nitric acid in the detector compartment to detect folic acid. A phosphate buffer (pH 6, 10 mM) and a separation voltage of 2 kV gave the complete separation of vitamins in less than 130 s, with good reproducibility (RSDs less than 10%) and accuracy (error less than 9%). In addition, a methodological innovation integrating calibration and analysis of water-soluble vitamins on the chip is also proposed. The strategy consisted in sequentially using both reservoirs (named calibration and analysis reservoirs) as well as a calibration factor (defined as signal/concentration of analyte). The analytical route required 350 s in the overall protocol (employing 130 s in calibration plus 130 s in analysis), an improvement over the times used in both conventional and microchip protocols.