Molecular mass spectrometric imaging of amino acids in dietary supplement tablets using laser ablation-atmospheric pressure chemical ionization-trapped ion mobility spectrometry-mass spectrometry

A UV laser ablation system coupled to atmospheric pressure chemical ionization-trapped ion mobility spectrometry-mass spectrometry (LA-APCI-TIMS-MS) is presented as a novel mass spectrometry imaging (MSI) tool to investigate the distribution of amino acids and vitamins in dietary supplement tablets. The setup employs a custom-built LA interface for commercially available APCI sources. Average single pulse response (SPR) durations of less than 0.2 s full peak width at 1 % maximum (FW0.01 M) were achieved. Imaging analyses resulted in the detection of 16 amino acids and 10 vitamins, all with unique and complementary distributions that are in most cases heterogeneously distributed over the sample surface. To differentiate between leucine and isoleucine, a second analysis was conducted on the same amino acid tablet with TIMS, showing distinct distributions for the two compounds. These results illustrate the potential of the presented setup to gain insight into the composition and manufacturing conditions of dietary supplements.