AMPEROMETRIC FLOW-THROUGH BIOSENSOR FOR THE DETERMINATION OF PESTICIDES

An amperometric flow-through biosensor for the determination of pestic ides is proposed. It is based on the inhibition of the acetyl cholines terase-catalysed hydrolysis of 4-aminophenylacetate. The calibration g raphs were linear from 5.0 X 10(-7) to 1.0 X 10(-5) M and; 5.0 X 10(-7 ) to 5.0 X 10(-5) M for paroxon and carbaryl, respectively. The detect ion limit (5% of inhibition) was 1.0 X 10(-7) M pesticide. The relativ e standard deviations (R.S.D.) (n = 5) were 3.7% for 4.0 X 10(-5) M an d 4.0% for 8.0 x 10(-6) M for either carbaryl or paroxon. Electroactiv e species such as uric and ascorbic acid and benzaldehyde that could b e oxidized at the same potential as 4-aminophenol, do not interfere. H owever, compounds which strongly absorb onto the electrode surface, su ch as bovine serum albumin (BSA) and surfactants capable of denaturing the enzyme activity, cause an interference. The stability of the sens or was high and even after repetitive use for one month the electrode retained 90% of its original activity. The determination of carbaryl a nd paroxon was carried out in lagoon water and kiwi fruits. The lowest concentration of pesticide determined in lagoon water was 1.0 x 10(-7 ) M for paroxon and 4.0 x 10(-7) M for carbaryl.