Molecularly imprinted polymer-modified electrode for on-line conductometric monitoring of haloacetic acids in chlorinated water

A conductometric sensor for on-line testing of haloacetic acids has been developed based on lab-on-chip device incorporated with an integrated miniaturised liquid-handling system. The sensor utilises a molecularly imprinted polymer (MIP) synthesized by the interaction between trichloroacetic acid (TCAA) template and a functional monomer, 4-vinylpyridine (VPD), together with cross-linking polymerisation of ethylene glycol dimethacrylate (EDMA). The ability of this MIP to change its conductivity in the presence of the target molecule into the imprint cavity has been used to develop the sensor, which responds well to TCAA in a continuous flow system with relatively good linearity, although this depends on the applied frequency. Thermal influences on the resistance of the sensor were in the order of 1.45% resistance signal variation per Kelvin at 3 kHz. The sensor showed high specific sensitivity to the target analyte and a stable and reasonable signal response in a solution containing inorganic anions. The sensitivity (range 0.5-5 œg l-1) and selectivity achieved with standard TCAA and five other haloacetic acids (HAAs) (dichloro-, monochloro-, tribromo-, dibromo-, and monobromoacetic acid) in water was good. Minimum sample volume required is 2.5 ml and the assay time is 2 min. The sensor has successfully been applied to haloacetic acid determination in domestic and commercial drinking water samples. Œ 2006 Elsevier B.V. All rights reserved.