Analysis of Microcystins in Drinking Water by ELISA and LC/MS/MS

摘要

Enzyme-linked immunosorbent assay (ELISA) and liquid chromatography/tandem mass spectrometry (LC/MS/MS) were compared for analyzing microcystins in water. ELISA results of microcystin-LR spiked into raw water samples were close to the spike concentrations, but method variability was ±25%. However, ELISA-derived microcystin- LA concentrations were two to three times higher than the spike concentrations obtained using the kit-provided microcystin-LR standards, indicating the need for variant-appropriate ELISA standards. LC/MS/MS results agreed with spike concentrations for all variants in reagent water, but matrix suppression was observed in some raw waters. In bench-scale studies, ozonated microcystins generated low-level positive responses by ELISA and a protein phosphatase inhibition assay, even though microcystins were not detected by LC/MS/MS. These findings indicate that ELISA results—particularly in treated water—should be interpreted with caution because of the possibility of false-positives, relatively high variability, and differential detection of some variants.