A new method for analysis of underivatized free β-methylamino-alanine: Validation and method comparison. (October 2016) - Rosén, Johan
Abstract: A new method was developed for analysis of free β-Methylamino-alanine (BMAA) in biological matrices. The method is based on direct analysis of the underivatized molecule, using an amide column for separation by Hydrophilic Interaction Liquid Chromatography (HILIC) and detection by tandem mass spectrometry (MS/MS) using a deuterium labeled internal standard. The use of Ultra-High Performance Liquid Chromatography (UHPLC) combined with MS/MS detection allowed for high chromatographic resolution and a low limit of detection (0.025 μg/g wet weight (ww) in mussels). The method was validated by analyzing spiked blank mussels from the Baltic Sea (0.15–4.4 μg/g (ww), trueness 99%–105%, RSD 2%–8%). An inter-laboratory comparative analysis of extracts of mussel was performed. The mussels were extracted according to an established protocol for analysis of free BMAA, and the extracts were then analyzed in parallel by the new method and a validated procedure based on detection of BMAA derivatized with dansyl chloride. Both methods detected BMAA in similar concentrations. Thus, derivatization with dansyl chloride did not influence the results compared to direct detection. The new method presents an alternative to the commonly applied derivatization step, and is proved through validation and method comparison to reliably identify and quantify free BMAA at low concentration levels. Highlights: A new sensitive and reliable method for direct detection of free β-methylamino-alanine is presented. The method makes use of an amide column for HILIC and detection by UHPLC-MS/MS. The new method allows for high chromatographic resolution and a low LOD (0.025 µg/g) and LOQ (0.15 µg/g) for mussels (ww). An inter-laboratory comparison of two methods showed quantitative agreement for extracts of mussel. Since earlier studies proved BMAA formation from low MW compound(s) during extraction, the detection step was investigated.