A New on-Column Conductivity Detection for Microchip Based on Accessional Solution Conductor Between Separation Channel and Electrodes
A new on-column conductivity detection for microchip capillary based on the accessional solution conductor between separation channel and electrodes was designed.In this detection,the carrier electrolyte solution was chosen as conductor to eliminate large drifts of the detection signals,that because different composition or concentration can lead to transport processes(diffusion and electromigration)between the carrier electrolyte solution and mediator.The separation channel incorporated a dual-T and a crux-channel,dual-T was used for sample introduction,and the crux-channel was used for detection.The sensing electrodes connected to separation channel through the crux-channel and obtained the potential different of conductivity.This method avoids integrating the sensing electrodes directly within the separation channel and prevents any direct contact of the electrodes with the sample.It not only avoids electrode reactions but also is convenient for washing and replacing electrodes.In addition,the signals,contrary to contactless conductivity detection,can be detected in the low excitation voltage(2.5-4.0 V)and frequency(700-1700 Hz)range.In the buffer solution of 15 mmol/L MES-His(pH 5.8),the detection limits was 0.5 and 0.1 μmol/L for K+ and Na+.