Micromachined electrophoresis chips with electrochemical detectors for analysis of explosive compounds in soil and groundwater

A capillary electrophoresis (CE) microsystem with amperometric detection has been developed to form a reusable, sensitive, and low-cost analytical device. As part of an electrochemical detection system, the working gold electrode was inserted into a specially designed detection cell, with its sensing area positioned just outside the separation channel outlet to provide high-sensitivity detection with negligible interferences from the separation electric field. Electrophoretic separations of trinitrotoluene (TNT) and four other nitroaromatic explosives in under 4 min with detection limits of 100-200 mu g/L demonstrated the good resolution as well as sensitivity of the CE microchip. The system was applicable for analysis of the explosive content of soil extracts and groundwater, yielding results in good agreement with the standard procedure. This truly reusable detection system is particularly useful for several applications that require frequent surface cleaning or electrode replacement due to severe surface poisoning.