A novel analytical method based on hybrid trapped ion mobility spectrometry-time-of-flight mass spectrometry (TIMS-TOFMS) has been developed to achieve fast enantiomeric separation of amino acids (AAs). Resolution of chiral AAs was achieved by forming diastereomers through derivatization with the chiral agent (+)-1-(9-fluorenyl)ethyl chloroformate (FLEC), avoiding the use of reference compounds. Electrospray ionization (ESI) in positive mode yielded sodiated FLEC-AAs ions of which the diastereomers could be separated by TIMS. The effect of other alkali metal ions (such as Li and K) on the enantioselectivity was studied, but chiral discrimination was only observed for Na. TIMS conditions, including voltage ramp, ramp time, and accumulation time were optimized for each AA, and collision cross sections (CCSs) were determined for all diastereomers. The migration order of the DL enantiomers was found to be dependent on the structure of the AA. The resulting TIMS resolution (K0/ΔK0) for the FLEC-AA diastereomers on average was 115, requiring a mobility (K0) difference of about 0.009 cm 2 /(V s) to achieve 50%-valley separation. From the 21 AAs studied, enantiomer separation was achieved for 17 AAs with mobility differences ranging from 0.009 for lysine up to 0.061 cm 2 /(V s) for asparagine. Moreover, the presented methodology provided mutual separation of various AAs, allowing chiral analysis of multiple AAs simultaneously which may be challenging with previous enantioselective IMS approaches. It appeared possible to fully resolve all studied DL-AAs using three distinct TIMS methods, resulting in a total MS run time of about 3 min (1 min per method) and a total analysis time (including derivatization) of less than 15 min. The method demonstrated capable to determine enantiomeric ratios down to 2.5% with detection limits for the D enantiomers in the nanomolar range. This new TIMS-based methodology opens up possibilities for easy and fast analysis of AA enantiomers.

The always more-demanding fields of food safety, quality and traceability are continuously fostering the development of robust, efficient, sensitive and cost-effective analytical methodologies. Mass spectrometry-based metabolomics is a key tool nowadays with great potential in many analytical fields and has been demonstrated to be capable of facing some important challenges related to these areas within the food science domain. The main aim of this review is to present a critical overview of the most recent applications of MS-based metabolomics approaches for food quality, safety and traceability assessment, covering the most relevant works published from 2014 to 2017. Information about the different steps needed to develop a MS-metabolomics approach, i.e. sample treatment, analytical platform, and data processing, is also provided and discussed.

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There are hundreds of non-protein amino acids whose importance in food and biological matrices is still unknown. Many of these compounds mainly exist in food as products formed during food processing, as metabolic intermediates or as additives to increase nutritional and functional properties of food. Moreover, they have also demonstrated to play an important role in the pharmaceutical and clinical fields since they may be used therapeutically in the treatment of some pathologies and their levels may be related with some diseases. For this reason, the analysis of non-protein amino acids may provide relevant information in the food and biological fields.This article reviews the most recent advances in the development of analytical methodologies employing capillary electrophoresis for the achiral and chiral analysis of non-protein amino acids in food and biological samples. With this aim, the most relevant information concerning the separation and detection of these compounds by capillary electrophoresis is discussed and detailed experimental conditions under which their determination was achieved in food and biological samples are given covering the period of time from 2015 to 2018.