Automation of immunochemical analysis?A prototype instrument to determine diuron or atrazine in water

Abstract

A prototype system of an automated, computer-controlled immunochemical analysis for pesticide residues in water will be described. This system is based on flow-injection analysis. The immunochemical reaction, which is the fundamental and specific part of this technique, is carried out in an immunoaffinity column with protein A on a polymetacrylate surface. Antipesticide antibodies, pesticide standard or water sample, enzyme tracer, and substrate for the enzyme reaction are pumped sequentially into this column. The measurement of one sample currently needs 1 hour and 45 minutes, which includes the preceding measurement of a control value. The fluorescence of the product of the enzyme reaction is expressed as percentage of control (zero standard, set as 100%). Within a European demonstration project (program Life), measurements are currently carried out for phenylurea and s-triazine herbicides (diuron and atrazine) in order to show the suitability of this technique as an on-line monitoring system and as an automated laboratory instrument. Standard curves for diuron and atrazine showed ranges of detection from 0.02 to 0.5 μg/L. For a simulation of real water samples, mixtures of diuron with four different concentrations of monuron, atrazine, and isoproturon, respectively, were measured. Nearly all mixture combinations showed a decrease in signal in comparison to the determination of diuron alone. In a first study of real water samples, flow-injection immunoaffinity analysis (FIIAA) proved to be suitable for the exclusion of negative samples. For the extension of the time of unattended operation, the immunoreagents were stabilized with 1% BSA and 0.5% micro-O-protect. This enabled the measurement for at least 1 week without a major decline in the signal caused by aging of the immunoreagents. © 1997 John Wiley & Sons, Inc. Lab Robotics and Automation 9: 81–89, 1997.