Detection and quantification of β-methylamino-L-alanine in aquatic invertebrates

Stephanie J. Christensen, Thomas K. Hemscheidt, Henry Trapido-Rosenthal, Edward A. Laws, Robert R. Bidigare

Limnol. Oceanogr. Methods 10:891-898 (2012) | DOI: 10.4319/lom.2012.10.891

ABSTRACT: β-N-methylamino-L-alanine (BMAA) is an excitotoxic neurotoxin that has been implicated in the etiology of Amyotrophic Lateral Sclerosis-Parkinsonism-Dementia Complex in the South Pacific island of Guam. BMAA has been reported to be present in a wide range of cyanobacteria taxa and aquatic invertebrates. However, there are large uncertainties in the human health risks associated with BMAA exposure because of the analytical challenges associated with the detection and quantification of BMAA. Here we describe an improved liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) method for the analysis of BMAA in aquatic invertebrate sample matrices, and present initial findings for oysters and blue crabs collected in the southeastern United States. The LC-MS/MS method is linear over a wide range of BMAA concentrations (0.4-153.2 pg μL-1, r2 = 0.997), and analytically precise, with a relative standard deviation (RSD) of 2.4%. The on-column limit of detection (LoD) and limit of quantification (LoQ) values for this method were determined to be 5 pg (0.2 pg μL-1) and 17 pg (0.8 pg μL-1), respectively. We observed a weak ion enhancement effect of ~10% in a mollusk matrix that tested negative for BMAA. Analyte recovery for the method averaged 92% (8% RSD). BMAA concentrations for oysters and blue crabs ranged from 5 to 47 μg g-1 dry weight sample and are substantially lower than the concentrations reported previously with a nonspecific BMAA method that was based on liquid chromatography-fluorescence detection (LC-FL). We conclude that BMAA analysis via LC MS/MS methodologies is absolutely necessary for obtaining reliable data.