Fast quantification of free amino acids in food by microfluidic voltage–assisted liquid desorption electrospray ionization–tandem mass spectrometry

• Published in: Analytical and bioanalytical chemistry 2020-03, Vol.412 (8), p.1947-1954
• Main Authors: Hu, Hankun, Smith, Shila, Li, Xiangtang, Qian, Zhengming, Su, Yaxia, Lin, Manting, Tu, Jiancheng, Liu, Yi-Ming
• Format: Article
• Language: English
• Subjects: Amino acids; Amino Acids - analysis; Analysis; Analytical Chemistry; Arginine; Aspartic acid; Biochemistry; Characterization and Evaluation of Materials; Chemistry; Chemistry and Materials Science; Desorption; Deuteration; Electric potential; Electrospraying; Food; Food analysis; Food Analysis - methods; Food Science; Fungi; Glutamic acid; Ionization; Ions; Laboratory Medicine; Mass spectrometry; Mass spectroscopy; Microfluidics; Monitoring/Environmental Analysis; Phenylalanine; Quality assessment; Quality control; Reproducibility; Research Paper; Scientific imaging; Spectrometry, Mass, Electrospray Ionization - methods; Spectroscopy; Spectrum analysis; Tandem Mass Spectrometry - methods; Tryptophan; Tyrosine; Voltage
• ISSN: 1618-2642; 1618-2650
• DOI: 10.1007/s00216-020-02450-w

A method based on microfluidic voltage–assisted liquid desorption electrospray ionization–tandem mass spectrometry (VAL-DESI-MS/MS) has been developed for fast quantification of free amino acids in food. Food extracts were transferred to the microfluidic platform and analyzed by liquid desorption ESI-MS/MS. Deuterated aspartic acid (i.e., 2,2,3-d 3 -Asp) was used as internal standard for analysis. The method had linear calibration curves with r 2 values > 0.998. Limits of detection were at the level of sub μM for the amino acids tested, i.e., glutamic acid (Glu), arginine (Arg), tyrosine (Tyr), tryptophan (Trp), and phenylalanine (Phe). To validate the proposed method in food analysis, extracts of Cordyceps fungi were analyzed. Amino acid contents were found in the range from 0.63 mg/g (Tyr in Cordyceps sinensis ) to 4.44 mg/g (Glu in Cordyceps militaris ). Assay repeatability (RSD) was ≤ 5.2% for all the five amino acids measured in all the samples analyzed. Recovery was found in the range from 95.8 to 105.1% at two spiking concentrations of 0.250 mg/g and 1.00 mg/g. These results prove that the proposed microfluidic VAL-DESI-MS/MS method offers a quick and convenient means of quantifying free amino acids with accuracy and repeatability. Therefore, it may have potential in food analysis for nutritional and quality assessment purposes. Graphical abstract