A new, versatile field immunosensor for environmental pollutants

This paper presents a new, versatile, portable miniaturized flow-injection immunosensor which is designed for field analysis. The temperature-controlled field prototype can run for 6 h without external power supply. The bio-recognition element is an analyte-specific antibody immobilized on a gold surface of pyramidal structures inside an exchangeable single-use chip, which hosts also the enzyme-tracer and the sample reservoirs. The competition between the enzyme-tracer and the analyte for the antigen-binding sites of the antibodies yields in the final step a chemiluminescence signal that is inversely proportional to the concentration of analyte in the given range of detection. A proof of principle is shown for nitroaromatics and pesticides. The detection limits (DL; IC20) reached with the field prototype in the laboratory was below 0.1 μg l−1 for 2,4,6-trinitrotoluene (TNT), and about 0.2 μg l−1 for diuron and atrazine, respectively. Important aspects in this development were the design of the competition between analyte and enzyme-tracer, the unspecific signal due to unspecific binding and/or luminescence background signal, and the flow pattern inside the chip.