Evaluation of an ELISA Kit for the Monitoring of Microcystins (Cyanobacterial Toxins) in Water and Algae Environmental Samples

A recently developed commercial microtiter plate ELISA test kit for microcystins was evaluated for its reproducibility, accuracy, detection limits in real samples, and comparability to results obtained from solid-phase extraction followed by liquid chromatography. Detection limits in the deionized water matrix were 0.05 μg/L, and the overall intra- (two to five replicates) and interkit (three replicates) reproducibility at this level was good (%CV < 10%). Various types of groundwater and surface water samples gave a matrix effect at low concentration levels so that limits of detection were obtained in the range 0.1−0.15 μg/L with the possibility of obtaining a false positive in this range. The limits of quantification were measured at 0.2 μg/L in several types of surface water samples. A fast and simple enrichment step using disposable C18 cartridges allows lower detection limits and is recommended in order to avoid a false positive. No false negative measurements were detected. Reliable correlations between measurements obtained by ELISA and by solid-phase extraction followed by liquid chromatography were obtained in spiked drinking and surface water samples (n = 8, r 2 = 0.989). In algae samples, the occurrence of several microcystins which may cross-react was shown using mass spectrometry but could not be confirmed due to the lack of commercially available standards. Overall, the assay illustrated the ability to measure concentrations of microcystins-LR and -YR in the range 0.2−4 μg/L in any type of surface water, allowing thus rapid and on-site detection of toxins in cyanobacterial blooms without any pretreatment.