Elucidation of matrix effects and performance of solid-phase extraction for LC-MS/MS analysis of β-N-methylamino-l-alanine (BMAA) and 2,4-diaminobutyric acid (DAB) neurotoxins in cyanobacteria

Abstract

A liquid chromatography-mass spectrometry (LC-MS/MS) method using hydrophilic interaction liquid chromatography (HILIC) was developed for the analysis of neurotoxins β-N-methylamino-L-alanine (BMAA) and 2,4-diaminobutyric acid (DAB), using multiple reaction monitoring (MRM) scan mode. Oasis-MCX and Strata-X-C polymeric cation-exchange cartridges were used to clean extracts of cyanobacterial cultures, including two strains of Microcystis aeruginosa and one strain of Nostoc sp. The performance of the solid-phase extraction (SPE) cartridges for BMAA and DAB were evaluated using mixed standards and spiked cyanobacterial extracts, which demonstrated recoveries of BMAA and DAB ranging from 66% to 91%. Matrix effects in LC-MS/MS were evaluated, and while there was no effect on BMAA quantitation, suppression of DAB was found. Full scan (Q1) and enhanced product ion (EPI) monitoring showed that the DAB suppression may be due to closely eluting compounds, including lysine, histidine, arginine and three other compounds with [M + H](+) m/z of 88, 164 and 191. The procedures developed allow the sensitive and effective analysis of trace BMAA and DAB levels in cyanobacteria. While DAB was confirmed to be present, no BMAA was found in the cyanobacterial samples tested in the present study.

The neurotoxin BMAA in aquatic systems : analysis, occurrence and effects

“…For sixteen methods, most data needed for method validation (detection limits, linear range, precision and recovery) were provided [34,76,79,82,93,94,100,105,111,121,122,135,145,148]. However, unvalidated methods (or methods for which no sufficient validation data were provided) were repeatedly referred to as 'validated'.…”

“…However, nearly all underivatised MS(/MS) studies have anticipated this by determining recovery [77,78,93,102,120], by using matrix based calibration curves [79] or by using D 3 BMAA as an internal standard [76,93]. In these studies, recovery rates generally exceed 80% and matrix based calibration curves have similar slopes as neat curves, so there is no indication that strong signal suppression indeed occurs 5 in real samples.…”

“…However, other laboratories could not detect BMAA in any cyanobacterial sample (e.g. [76][77][78][79]), although the analytical methods used were in most cases sensitive enough to enable reproduction of these first results. The claim that 14 …”

“…Most evidence for correct BMAA analysis is provided in sixteen studies [76][77][78][79]83 disclosure, or availability of sample material for comparative analyses is essential to improve the current state of knowledge in BMAA research.…”

“…LC-FLD^ Y + + + + + + + + + x + -+ -+ -+ + p p p p [79] LC-MS/MS N + + + + + x + + + + + + + + + + + + + + + + [96] LC β-N-Methylamino-L-alanine (BMAA) is a neurotoxin that is suspected to play a role in the neurological diseases amyotrophic lateral sclerosis, Alzheimer's disease and Parkinson's disease. BMAA has been detected in phytoplankton and globally, the main exposure routes for humans to BMAA are through direct contact with phytoplankton infested waters and consumption of BMAA contaminated fish and invertebrates.…”