Determination of traces of several pesticides in sunflower oil using organic phase immuno electrodes (OPIEs)

• New immunosensors working in organic solvent mixtures (OPIEs) were developed.
• Traces of different pesticides were tested in sunflower oil using OPIEs.
• Immunosensors show satisfactory selectivity and precision.
• Recovery tests in commercial sunflower oil samples gave excellent results.
• OPIEs act positively in organic solvent as shown by Hill׳s coefficient values.

Testing for traces of different pesticides (triazinic, organophosphates and chlorurates), present in hydrophobic matrices such as sunflower oil was checked using new immunosensors working in organic solvent mixtures (OPIEs). The competitive process took place in an n-hexane–chloroform 75% (V/V) mixture, while the subsequent final enzymatic measurement was performed in decane using tert-butylhydroperoxide as substrate of the enzymatic reaction. A Clark electrode was used as transducer and peroxidase enzyme as marker. A linear response of between about 10 nM and 4 μM was usually obtained in the presence of sunflower oil. Immunosensors show satisfactory selectivity and precision and recovery tests carried out on commercial sunflower oil samples gave excellent results. Lastly, theoretical confirmation of the possibility that immunosensors can act positively in organic solvent mixtures was discussed on the basis of Hill׳s coefficient values.

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