Determination of 3,5,6-trichloro-2-pyridinol (TCP) in water by a continuous competitive immunoassay system based on the streptavidin-biotin interaction.

A competitive continuous immunoassay system for the determination of 3,5,6-trichloro-2-pyridinol (TCP), the major degradation product of the insecticide chlorpyrifos, in water is described. The immunoassay system is based on the transient retention of the specific LIB-MC2 monoclonal antibody anti-TCP as a biotinylated derivative using the streptavidin-biotin interaction. The permanent immobilization of streptavidin on controlled-pore-glass provides an adequate active support for the transient retention of the biotinylated monoclonal antibody anti-TCP. In a subsequent step, the immuno-competitive reaction between the biotinylated LIB-MC2 and the TCP/hapten-POD mixture takes place. This competitive assay relies on the determination of the biocatalytic action of peroxidase, retained in the active support, on a derivatization reaction which yields a fluorescent product. The method exhibits a determination range of 0.01-200 microg L(-1) of TCP (r2=0.9919, n=9) with a precision, expressed as RSD, lower than 4.2% and a sampling frequency of 3 h(-1). The approach has been applied to the determination of TCP in water with recoveries of 89.7-105.6%.

Inhibition-based determination of metrifonate in liquid and solid samples using the triple integration chemical hydrolysis-pervaporation-enzymic derivatisation.

An innovative continuous flow approach consisting of the triple integration of chemical hydrolysis, analytical pervaporation and enzyme inhibition-based reaction for the determination of metrifonate is presented. The method is based on chemical degradation of the pesticide, a separation step consisting of analytical pervaporation of its volatile metabolite and inhibition action of this on the acetylcholinesterase catalysis. The subsequent derivatisation reaction is a two-step reaction involving choline oxidase (ChOD) and horseradish peroxidase (POD) with fluorimetric detection (lambda (ex )=310 nm and lambda (em )=415 nm ) of the dimer formed by the action of hydrogen peroxide. The efficiency of the inhibitory effect was increased using an open-closed flow system. Applied to liquid samples, the method has a linear determination range of 0.0025-0.15 g l(-1)(n=8, r=0.9993) with a precision, expressed as RSD, of 3.2-6.7% and a sampling frequency of 3 h(-1). When applied to solid samples the method shows a linear determination range of 0.0026-0.13 g kg(-1) (n=5, r(2)=0.9981, RSD 2.7-7.7%) and a sampling frequency of 2h(-1). The approach has been applied to the determination of metrifonate in natural water and spiked soil samples with recoveries ranging between 94.3 and 107.8% for liquid samples and between 86.5 and 99.6% for solid samples.