Evaluation of laboratory methods for the analysis of microcystins

Finding low cost, rapid tests to monitor microcystins in water is paramount to protect environmental and public health worldwide. Bioassays like Protein Phosphatase Inhibition Assay (PPIA) and Enzyme-linked Immunosorbent Assay (ELISA) have many advantages over liquid chromatography–tandem mass spectrometry (LC-MS/MS). Analytical cost per sample was found to be $136 by ELISA and $365 by LC-MS/MS. An agreement of 76% was found between ELISA and LC-MS/MS results from 2010 to 2012 (n=854) on the basis of Method Detection Limits (MDLs). Among samples with LC-MS/MS results >1.5μg/L, ELISA missed 3 samples in 2010, 1 in 2011 and none in 2012. Correlation between PP2A and ELISA was strong (R2=0.8155, p=0.8054, n=27) in surface water samples but non-existent in drinking water (R2=0.0366, p=0.0665, n=38). PP2A was found useful for monitoring non-coloured surface water but not for drinking water. A 2-tier test system is proposed: tier-1 ELISA and tier-2 PP2A for surface water samples.