Validation of an enzymatic biosensor with various liquid chromatographic techniques for determining organophosphorus pesticides and carbaryl in freeze-dried waters

✍ Scribed by J.L Marty; N. Mionetto; S. Lacorte; D. Barceló

• Publisher: Elsevier Science
• Year: 1995
• Tongue: English
• Weight: 615 KB
• Volume: 311
• Category: Article
• ISSN: 0003-2670
• DOI: 10.1016/0003-2670(94)00617-u

✦ Synopsis

An enzymatic biosensor based on the reaction of acetylthiocholine chloride, which is enzymatically hydrolysed to thiocholine giving a disulphide compound by dimerization, was validated with various liquid chromatographic techniques for determining the organophosphorus pesticides fenitrothion, fenamiphos, parathion-ethyl and the carbamate pesticide cabaryl in two different batches of freeze-dried waters at levels varying from 0.1 to 5.7 pg 1 -' for each individual compound. Calibration graphs for the biosensor were performed for a concentration range of 1 X 1O-5-1 X 10-r' M for paraoxon, and the limit of detection was taken as the insecticide concentration that resulted in 10% inhibition of the enzyme activity. Depending on the liquid chromatographic systems used -either liquid-liquid extraction of 1 1 water with dichloromethane or an on-line automated precolumn exchange system (Prospekt) of 100 ml water -followed by liquid chromatography with diode array detection, good reproducibility was obtained between 0.05 and 10 pg I-', the limit of detection lying between 0.01 and 0.05 pg l-r, depending on the compound. The determination of the total amount of pesticides by the biosensor was carried out either after liquid-liquid extraction or using a flow-injection system. In both cases the batch of water containing the higher amount of pesticides gave also a higher signal when using the biosensor. The total amount of pesticide determined with the biosensor could be used as a positive indication of the presence of the target pesticides at a level of 3.9-10.3 Fg 1-l total target pesticides present in the sample.