Antibody-based methods for surfactant screening

This brief overview summarises the immunoassay-based results obtained in th e course of two years of the European INCO-Copernicus project BIOTOOLS. The project is aimed at simplifying the procedures for detection of surface ac tive compounds (SAC) using, among others, antibody-based methods, i.e., mic rotiter plate-based enzyme-linked immunosorbent assays (ELISA), polarisatio n fluoro immunoassays (PRA), and enzyme flow injection immunoassays (FIIA). Thirty-three rabbits were immunised with five different sulphophenyl moiet ies and three p-hydroxyphenyl moieties conjugated to protein immunogens to produce analytical antibodies against linear alkylbenzene sulphonates (LAS) and nonylphenol (NP). Although most of the antibodies exhibited binding re action in indirect ELISA, only a few showed the required assay sensitivity. The best antibodies for LAS exhibited a 50% binding inhibition at IC50 19. 8 mug L-1 in indirect ELISA. Similar inhibition was observed for direct ELI SA using peroxidase tracers. Antibodies against NP allowed the establishmen t of an indirect assay operating in the mg L-1 range. A rapid and simple pr otocol for the screening of NP and LAS using homogeneous PFIA is described. The assay time for 10 samples was 7 minutes, thus allowing fast detection of the selected SAC at the mg L-1 level. A generic competitive FIIA system, using a protein G column for separation of free and antibody-bound beta -g alactosidase (beta -Gal) tracer, was developed for the screening of LAS, NP , and nonylphenol decaethoxylate (NPEO10). The FIIA had a sample throughput (STP) of 5-10 samples per hour, with limits of detection (LOD) for LAS, NP , and NPEO10 of 19.5, 52, and 2.4 mug L-1, respectively. The developed FIIA s were applied to spiked rain and surface water.