Analysis of mycosporine-like amino acids in plankton by liquid chromatography electrospray ionization mass spectrometry

Mycosporine-like amino acids (MAAs) are small, water-soluble compounds with the putative biological function of serving as screens against ultraviolet (UV) radiation. Thus far, these compounds are usually characterized and quantified by based on their retention time during high-performance liquid chromatography (HPLC) and by their characteristic UV absorption patterns or absorption maxima. To allow for better assessment of compound diversity in plankton, we implemented electrospray ionization mass spectrometry coupled with liquid chromatography (LC/MS) for MAA characterization and quantification. Quantitative mass spectral analysis of MAAs with respect to an -tyramine hydrochloride internal standard was found to have a precision of better than 3% and a detection limit of 2.0 pg. Overall, this method adds another level in MAA elucidation by providing the molecular weight and/or fragmentation pattern of each constituent. Using a data matrix of retention time, absorption maximum, and molecular weight, the identity of the MAAs can be unambiguously established. Mass spectrometry also provides a means to better characterize novel MAAs and MAA degradation products in general.