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 Original Research Article

A new immunosorbent involving antigen–antibody interactions has been developed for the selective solid-phase extraction of microcystins (heptapeptides synthesised by cyanobacterial algae) in environmental samples. Its evaluation is first described as off-line solid-phase extraction followed by liquid chromatography or microchromatography. Due to the high affinity and selectivity of the antigen–antibody interactions, extraction, concentration and isolation of microcystins in complex samples occur in a single step. Selectivity is shown by the analysis of real samples and by comparison with the use of non-specific octadecylsilica extraction sorbent. Especially, it is demonstrated that potential interferences from herbicides are not trapped by the immunosorbent. Due to the cross-reactivity of the antibodies and the very similar molecular structures of the microcystin variants, the immunosorbent was shown to trap the three commercially available standards of microcystins, as well as other variants which occurred in algae cultures or real water samples and which have been identified using LC-mass spectrometry. In case of blooms, rapid on-site determinations are achieved by coupling immunoextraction to bioanalytical methods such as either a commercial ELISA kit or a phosphatase inhibition assay. The clean extracts free from any matrix interferences and the easy-to-obtain enrichment factor of 10 greatly improve the determination of microcystins at the 0.1 μg l−1 in surface water using these bioanalytical assays. The best available technique for a rapid monitoring of toxic blooms is the combination of a simple immunoextraction with the phosphatase inhibition test because it combines a structure recognition tool with a bioassay based on the toxicity mode.