Application of electrochemical detection for droplet-based microfluidics

Abstract

Here, an application of droplet-based microfluidics coupled with an electrochemical sensor using chronoamperometry with chip-based carbon paste electrodes (CPEs) for determination of dopamine (DA) and ascorbic acid (AA) was presented. Droplets were generated using an oil flow rate of 1.8 μL/min whereas a flow rate of 0.8 μL/min was applied for an aqueous phase, which given water fraction equal to 0.31. An optimum applied potential for chronoamperometric measurements in droplet was found to be 150 mV. Highly reproducible analysis of DA and AA was achieved with relative standard deviations less than 5% for both intraday and interday measurements. 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. The dynamic range 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 amount 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 0.9970 and 0.9982, respectively. Compared with the labeled amounts, the measured concentrations of DA and AA obtained from this system were slightly different with the error percentages of +1.8% for AA and in the range of -2.6 to -5.7% for DA, indicating high accuracy of the developed method.