Detection of organophosphate and carbamate pesticides in vegetable samples by a photothermal biosensor.

Previously developed photothermal biosensor was optimised by determining the most suitable enzyme substrate (acetylthiocholine iodide) and the optimal carrier buffer (0.05 M phosphate buffer, pH 8.0). Excitation laser operating at 488 nm and 120 mW power provided the highest biosensor sensitivity. The biosensor was tested for detection of toxic organophosphate and carbamate compounds present in samples of salad, iceberg lettuce, and onion. Sufficient sensitivities to different pesticides (carbofuran, propamocarb, oxydemeton-methyl and parathion-ethyl) were achieved without time-consuming sample preparation procedures. The results show good agreement with the concentrations of pesticides determined with standard GC-MS detection method. The developed photothermal biosensor offers new low cost means to detect low concentrations of pesticides in vegetable samples with high throughput and little or no sample pretreatment.