Water quality control in the production of drinking water from river water. The application of immunological techniques for the detection of chlorophenoxy acid herbicides (2,4-D)

In the production of drinking water from river water, the quality of the raw water is extremely important. For this reason the Water Transport Company Rhine-Kennemerland (WRK) operates, among others, an early warning system. This system was found to be inappropriate for the detection of certain chlorophenoxy herbicides (e.g., 2,4-D, MCPP, MCPA and 2,4-DP) that are occasionally found in the Rhine in increased levels (above the drinking water norm of 0.1 μg l−1). Commercially available immunoassay kits were evaluated for use in pre-screening. With some modifications to adapt the working range and to enhance the sensitivity of the kits, they were found to be applicable in the early warning. Comparison with a gas chromatography-mass spectrometry reference analysis revealed no false negative results and a rate of false positive results of about 10%. However, it should be taken into account that matrix effects may affect the results. A daily sampling frequency combined with an analysis frequency based on the actual flow in the river allowed for a periodic batchwise analysis. This permitted a timely availability of the results as well as a cost-effective use of the (modified) kits.