Integrated Identification and Quantification of Cyanobacterial Toxins from Pacific Northwest Freshwaters by Liquid Chromatography and High-resolution Mass Spectrometry

Abstract

The occurrence of harmful algal blooms in nutrient-rich freshwater bodies has increased world-wide, including in the Pacific Northwest. Some cyanobacterial genera have the potential to produce secondary metabolites that are highly toxic to humans, livestock and wildlife. Reliable methods for the detection of cyanobacterial toxins with high specificity and low limits of detection are in high demand. Here we test a relatively new hybrid high resolution accurate mass quadrupole time-of-flight mass spectrometry platform (TripleTOF) for the analysis of cyanobacterial toxins in freshwater samples. We developed a new method that allows the quantitative analysis of four commonly observed microcystin congeners (LR, LA, YR, and RR) and anatoxin-a in a 6-min LC run without solid-phase enrichment. Limits of detection for the microcystin congeners (LR, LA, YR, and RR) and anatoxin-a were <5 ng/L (200-fold lower than the guideline value of 1 μg/L as maximum allowable concentration of MC-LR in drinking water). The method was applied for screening freshwaters in the Pacific Northwest during the bloom and post-bloom periods. The use of high resolution mass spectrometry and concomitant high sensitivity detection of specific fragment ions with high mass accuracy provides an integrated approach for the simultaneous identification and quantification of cyanobacterial toxins. The method is sensitive enough for detecting the toxins in single Microcystis colonies.