Chlorophyll fluorescence biosensor for the detection of herbicides

A biosensor is described for the detection of triazine and phenylurea herbicides in drinking water by kinetic measurements of endogenous chlorophyll fluorescence in isolated chloroplasts from higher plants. The pocket-size device uses a diode laser for simultaneous excitation of sample and reference channels, and photodiodes for detection of the emitted light. The biological material can be supplied as a freeze-dried powder, stable for 21 days at room temperature, for 6 weeks at 4 ( degrees )C or for at least 9 months at -20 ( degrees )C. The detection of 0.1 microg/l of a single herbicide, as required by European Community legislation on drinking water quality, can be achieved without prior extraction of the sample.