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

A capillary electrophoresis (CE) microsystem with amperometric detection ha s been developed to form a reusable, sensitive, and low-cost analytical dev ice. As part of an electrochemical detection system, the working gold elect rode was inserted into a specially designed detection cell, with its sensin g area positioned just outside the separation channel outlet to provide hig h-sensitivity detection with negligible interferences from the separation e lectric field. Electrophoretic separations of trinitrotoluene (TNT) and fou r other nitroaromatic explosives in under 4 min with detection limits of 10 0-200 mu g/L demonstrated the good resolution as well as sensitivity of the CE microchip. The system was applicable for analysis of the explosive cont ent of soil extracts and groundwater, yielding results in good agreement wi th the standard procedure. This truly reusable detection system is particul arly useful for several applications that require frequent surface cleaning or electrode replacement due to severe surface poisoning.