Quantitation of chiral amino acids from microalgae by MEKC and LIF detection

In this work, chiral and non chiral MEKC methods have been combined with LIF detection (MEKC-LIF) to identify and quantify a group of D-and L-aminoacids (D/L-aa) in different microalgae samples. The combination of the non chiral and chiral-MEKC-LIF methods made the identification of the microalgae aminoacids easier, previously derivatized with FITC, providing a double proof on the correct detection of these analytes. Three microalgae species, Spirulina platensis, Dunaliella salina, and Tetraselmis suecica,were compared in terms of their content in D-Arg, L-Arg, D-Lys, L-Lys, D-Ala, L-Ala, D-Glu, L-Glu, D-Asp, and L-Asp. Also ,a comparison between two Spirulina platensis samples dried under different Conditions (i.e.,hot air or lyophilized)was carried out in order to investigate the effect of the thermal processing on the aminoacid content. Moreover, two procedures for the extraction of aminoacids from microalgae(i.e., a classical procedure and pressurized liquide xtraction (PLE)) together with different conditions for aminoacid derivatization were studied in order to increase the sensitivity of the whole analytical method. By using the selected chiral- MEKC-LIF conditions(100mMsodiumtetraborate,30mMSDS,and20mM b-CD at pH9.7) the main microalgae D/L-aa are separated in less than 25 min with efficiencies up to 840000 plates/m and good sensitivity (i.e.,330ng of D-Arg per gram ofmicroalga could be detected by this procedure for an S/N o f3). Several D-aa were detected in all the microalgae, observing interesting differences in their D/L-aa profiles, what corroborates the usefulness of the chiral-MEKC-LIF approach to characterize different microalgae species aswell as different microalgae drying processes. Moreover,the use of PLE can selectively extract different free aminoacids from microalgae.