Potential of immunoextraction coupled to analytical and bioanalytical methods (liquid chromatography, ELISA kit and phosphatase inhibition test) for an improved environmental monitoring of cyanobacterial toxins

A new immunosorbent involving antigen-antibody interactions has been develo ped for the selective solid-phase extraction of microcystins (heptapeptides synthesised by cyanobacterial algae) in environmental samples. Its evaluat ion is first described as off-line solid-phase extraction followed by liqui d chromatography or microchromatography. Due to the high affinity and selec tivity of the antigen-antibody interactions, extraction, concentration and isolation of microcystins in complex samples occur in a single step. Select ivity is shown by the analysis of real samples and by comparison with the u se of non-specific octadecylsilica extraction sorbent. Especially, it is de monstrated that potential interferences from herbicides are not trapped by the immunosorbent. Due to the cross-reactivity of the antibodies and the ve ry similar molecular structures of the microcystin variants, the immunosorb ent was shown to trap the three commercially available standards of microcy stins, as well as other variants which occurred in algae cultures or red wa ter samples and which have been identified using LC-mass spectrometry. In c ase of blooms, rapid on-site determinations are achieved by coupling immuno extraction to bioanalytical methods such as either a commercial ELISA kit o r a phosphatase inhibition assay. The clean extracts free from any matrix i nterferences and the easy-to-obtain enrichment factor of 10 greatly improve the determination of microcystins at the 0.1 mu g l(-1) in surface water u sing these bioanalytical assays. The best available technique for a rapid m onitoring of toxic blooms is the combination of a simple immunoextraction w ith the phosphatase inhibition test because it combines a structure recogni tion tool with a bioassay based on the toxicity mode. (C) 1999 Elsevier Sci ence B.V. All rights reserved.