β-N-Methylamino-L-alanine (BMAA) is a non-protein amino acid produced by cyanobacteria that can accumulate in ecosystems and food webs. Human exposure to cyanobacterial and algal blooms may be a risk factor for neurodegenerative diseases such as Alzheimer's disease and amyotrophic lateral sclerosis. Analytical chemists have struggled to find reliable methods for BMAA analysis in complex sample matrices. Analysis of BMAA is complicated by at least 3 naturally occurring isomers: N-(2-aminoethyl)glycine (AEG), 2,4-diaminobutyric acid (DAB), and β-aminomethyl-L-alanine (BAMA). More than 350 publications have reported detection and quantification of BMAA and its isomers, but varying results have led to controversy in the literature. The objective of this study was to perform a single laboratory validation (SLV) of a frequently published method for BMAA analysis using a ZIC-HILIC column. We investigated the selectivity, linearity, accuracy, precision, and sensitivity of the method and our data show that this HILIC method fails many of the criteria for a validated method. The method fails the criterion for selectivity as the chromatography does not separate BMAA from its isomer BAMA. Sensitivity of the method greatly decreased over the experimental period and it demonstrated a higher limit of detection (LOD) (7.5 pg on column) and a higher lower limit of quantification (LLOQ) (30 pg on column) than other published validated methods. The method demonstrated poor precision of repeated injections of standards of BMAA with % relative standard deviation (%RSD) values that ranged from 37 to 107% while HorRat values for BMAA had a fail rate of 80% and BAMA had a fail rate of 73%. No HorRat values between 0.5 and 2 were found for repeated injections of standards of AEG and DAB. Recovery of 13C3,15N2-BMAA in a cyanobacterial matrix was < 10% in experiments and we were also unable to accurately detect other protein amino acids including methionine, cysteine, or alanine, indicating matrix effects. The results of this study demonstrate that the ZIC-HILIC column is not fit for purpose for the analysis of BMAA in cyanobacterial matrices and further provides explanations for the high level of negative results reported by researchers using this method.
Keywords: Amino acid analysis; Analytical methods; Cyanobacteria; HILIC; β-N-Methylamino-L-alanine (BMAA).