USE OF CONDUCTIVITY ELECTRODES AS ON-CHIP SENSORS IN CHROMATOGRAPHIC MICROFLUIDIC DEVICES

摘要

We report the use of direct-conductivity sensing as a means for measuring mobile-phase composition and flow rate inside an HPLC chromatography chip. Instantaneous on-chip solvent percentage during gradient elution is determined from the measured mobile-phase conductivity. The method can show changes in mobile phase organic solvent percentage of 1%, even at 90% acetonitrile. In addition, flow rates in the range of 100 to 1000 nL/min are determined by measuring the time-of-flight of a heat pulse as it moves from a heater trace to embedded conductivity sensing electrode.