Gas Chromatography-Mass Spectrometry Based Approach for the Determination of Methionine-Related Sulfur-Containing Compounds in Human Saliva

• Published in: International journal of molecular sciences 2020-12, Vol.21 (23), p.9252
• Main Authors: Piechocka, Justyna, Wieczorek, Monika, Głowacki, Rafał
• Format: Article
• Language: English
• Subjects: Acetonitrile; amino acid; aminothiol; Chemical bonds; Chromatography; cysteine; Deproteinization; Drying; Experiments; Gas chromatography; Gas Chromatography-Mass Spectrometry; Homocysteine; homocysteine thiolactone; Humans; Linearity; Mass spectrometry; Mass spectroscopy; Metabolism; Metabolites; Metabolomics - methods; Methionine; Methionine - metabolism; Physiology; Proteins; Pyridines; Reproducibility of Results; Saliva; Saliva - metabolism; Scientific imaging; Spectroscopy; Sulfur; Sulfur Compounds - metabolism; Thiolactone; Urine; Volatile compounds
• ISSN: 1422-0067; 1661-6596; 1422-0067
• DOI: 10.3390/ijms21239252

Gas chromatography-mass spectrometry technique (GC-MS) is mainly recognized as a tool of first choice when volatile compounds are determined. Here, we provide the credible evidence that its application in analysis can be extended to non-volatile sulfur-containing compounds, to which methionine (Met), homocysteine (Hcy), homocysteine thiolactone (HTL), and cysteine (Cys) belong. To prove this point, the first method, based on GC-MS, for the identification and quantification of Met-related compounds in human saliva, has been elaborated. The assay involves simultaneous disulfides reduction with tris(2-carboxyethyl)phosphine (TCEP) and acetonitrile (MeCN) deproteinization, followed by preconcentration by drying under vacuum and treatment of the residue with a derivatizing mixture containing anhydrous pyridine, -trimethylsilyl- -methyl trifluoroacetamide (MSTFA), and trimethylchlorosilane (TMCS). The validity of the method was demonstrated based upon US FDA recommendations. The assay linearity was observed over the range of 0.5-20 µmol L for Met, Hcy, Cys, and 1-20 µmol L for HTL in saliva. The limit of quantification (LOQ) equals 0.1 µmol L for Met, Hcy, Cys, while its value for HTL was 0.05 µmol L . The method was successfully applied to saliva samples donated by apparently healthy volunteers ( = 10).