Electrochemiluminescence enzyme immunoassay for TNT

Abstract

Details of an electrochemiluminescence (ECL) enzyme immunoassay for TNT (2,4,6-trinitrotoluene) are reported. The design and construction of a computer controlled flow injection electrochemiluminometer in which the immunoassays are carried out is described. This system is used to select and pump solutions through a flow cell, which contains a gold working electrode as part of a three-electrode arrangement. The deposition of a re-usable immunosorbent dextran surface anchored to a gold surface in the flow cell by chemiadsorbed thiol groups is described. Antibodies are labeled with the enzyme glucose oxidase and used in competitive immunoassays in which the separation step is carried out by concentrating unbound antibodies on the immunosorbent surface. Hydrogen peroxide generated by the enzyme label when glucose is pumped through the flow cell is detected using luminol ECL. Light intensity was inversely proportional to the concentration of TNT in the sample in the range 0–100 ppb. The results are compared with colorimetric ELISA's carried out using the same reagents, and potential for developing a portable instrument for use in the field is discussed.