Enzyme Immunoaffinity Chromatography—A Rapid Semi-quantitative Immunoassay Technique for Screening the Presence of Isoproturon in Water Samples

Abstract

Immunochromatography devices based on the principles of affinity chromatography and enzyme immunoassay have been developed to illustrate the possibility of providing extra-laboratory ‘in the field’ tests for pesticide monitoring. Isoproturon was chosen in this study as an example though other pesticides could have been used provided a suitable antiserum existed. The test system was prepared by immobilising isoproturon antibodies to porous silica which were then packed into disposable columns (immunoaffinity columns). The addition of chromagen–substrate 3, 3′, 5, 5′-tetramethylbenzidine into the immunoaffinity columns, after the application of a mixture containing an equal volume of isoproturon samples or isoproturon standard solutions with a fixed concentration of isoproturon labelled with horseradish peroxidase, allowed the development of a colorimetric portable assay capable of screening samples qualitatively for the presence of isoproturon in water. Samples with contamination levels of 0.12 µg l ^{- 1} isoproturon and above were visually identified as positive samples in comparison to the zero standard sample. However, samples with concentrations below this level would be considered as negative (no isoproturon present at this limit of detection). The duration of the sample screening procedure on the column was less than 25 min making the technique highly suitable for a rapid estimate of isoproturon concentrations. Furthermore, the system could estimate isoproturon concentrations in water from various sources with no requirement for sample preparation. Therefore, the technique is ideally suited for monitoring the presence of pesticides in water. Further refinement of the assay could result in a test suitable for use by non-skilled personnel in extra-laboratory locations (e.g., a mobile or field laboratory).