This paper presents the first example of a pharmaceutical application of droplet-based microfluidics coupled with chronoamperometric detection using chip-based carbon paste electrodes (CPEs) for determination of dopamine (DA) and ascorbic acid (AA). Droplets were generated using an oil flow rate of 1.80 μL min-1 , whereas a flow rate of 0.80 μL min-1 was applied to the aqueous phase, which resulted in a water fraction of 0.31. The optimum applied potential for chronoamperometric measurements in droplets was found to be 150 mV. Highly reproducible analysis of DA and AA was achieved with relative standard deviations of less than 5% for both intra-day and inter-day measurements. The limit of detection (LOD) and limit of quantitation (LOQ) were found to be 20 and 70 μM for DA and 41 and 137 μM for AA, respectively. Linearity of this method was in the ranges of 0.02-3.0 mM for DA and 0.04-3.0 mM for AA. This system was successfully applied to determine the amounts of DA and AA in intravenous drugs. Calibration curves of DA and AA for quantitative analysis were obtained with good linearity with R2 values of 0.9984 and 0.9988, respectively. Compared with the labeled amounts, the measured concentrations of DA and AA obtained from this system were insignificantly different, with error percentages of less than ±3.0%, indicating a high accuracy of the developed method.
Suea-Ngam, Akkapol, Poomrat Rattanarat, Orawon Chailapakul, Monpichar Srisa-Art
Analytica Chimica Acta