Abstract: A method for determining in a sample, by mass spectrometry, the amount of one or more analytes selected from the group consisting of N-acetylthreonine, TMAP, phenylacetylglutamine, tryptophan, creatinine, meso-erythritol, arabitol, myo-inositol, N-acetyl serine, N-acetylalanine, 3-methylhistidine, trans-4-hydroxyproline, kynurenine, urea, C-glycosyltryptophan, 3-indoxyl sulfate, pseudouridine, and combinations thereof is described. The method comprises subjecting the sample to an ionization source under conditions suitable to produce one or more ions detectable by mass spectrometry from each of the one or more of the analytes; measuring, by mass spectrometry, the amount of the one or more ions from each of the one or more analytes; and using the measured amount of the one or more ions to determine the amount of each of the one or more analytes in the sample. Also described is a kit comprising one or more isotopically labeled analogues as internal standards for each of the one or more analytes.

Abstract: A method for determining in a sample, by mass spectrometry, the amount of one or more analytes selected from the group consisting of 12,13-DiHOME, 3-hydroxybutyrate (BHBA), 3-hydroxyoctanoate, 3-methylglutarylcarnitine, 3-ureidopropionate, 7-alpha-hydroxy-4-cholesten-3-one (7-Hoca), citrate, fucose, fumarate, gamma-tocopherol, glutamate, glutarate, glycerol, glycochenodeoxycholate, glycocholate, hypoxanthine, maleate, malonate, mannose, orotate, 2,3-pyrdinedicarboxylate, ribose, serine, taurine, taurochenodeoxycholate, taurocholate, palmitoleate, linolenate, xanthine, xylitol, and combinations thereof is described.

Abstract: A method for determining the amount of one or more analytes in a sample by mass spectrometry is described. The one or more analytes are selected from the group consisting of alpha-hydroxybutyrate (2-HB), linoleoyl LPC (LGPC), oleic acid, 3-hydroxybutyrate (3-HB), 4-methyl-2-oxopentanoate (4-MOP), pantothenate, and serine. The method includes a) subjecting the sample to an ionization source under conditions suitable to produce one or more ions detectable by mass spectrometry from each of the one or more of the analytes, wherein the analytes are not derivatized prior to ionization; b) measuring, by tandem mass spectrometry, the amount of the one or more ions from each of the one or more analytes; and c) using the measured amount of the one or more ions to determine the amount of each of the one or more analytes in the sample.

Abstract: A method for determining in a sample, by mass spectrometry, the amount of one or more analytes selected from the group consisting of 12,13-DiHOME, 3-hydroxybutyrate (BHBA), 3-hydroxyoctanoate, 3-methylglutarylcarnitine, 3-ureidopropionate, 7-alpha-hydroxy-4-cholesten-3-one (7-Hoca), citrate, fucose, fumarate, gamma-tocopherol, glutamate, glutarate, glycerol, glycochenodeoxycholate, glycocholate, hypoxanthine, maleate, malonate, mannose, orotate, 2,3-pyrdinedicarboxylate, ribose, serine, taurine, taurochenodeoxycholate, taurocholate, palmitoleate, linolenate, xanthine, xylitol, and combinations thereof is described.

Abstract: A method for determining the amount of one or more analytes in a sample by mass spectrometry is described. The one or more analytes are selected from the group consisting of alpha-hydroxybutyrate (2-HB), linoleoyl LPC (LGPC), oleic acid, 3-hydroxybutyrate (3-HB), 4-methyl-2-oxopentanoate (4-MOP), pantothenate, and serine. The method includes a) subjecting the sample to an ionization source under conditions suitable to produce one or more ions detectable by mass spectrometry from each of the one or more of the analytes, wherein the analytes are not derivatized prior to ionization; b) measuring, by tandem mass spectrometry, the amount of the one or more ions from each of the one or more analytes; and c) using the measured amount of the one or more ions to determine the amount of each of the one or more analytes in the sample.

Abstract: A method for determining in a sample, by mass spectrometry, the amount of one or more analytes selected from the group consisting of N-acetylthreonine, TMAP, phenylacetylglutamine, tryptophan, creatinine, meso-erythritol, arabitol, myo-inositol, N-acetyl serine, N-acetylalanine, 3-methylhistidine, trans-4-hydroxyproline, kynurenine, urea, C-glycosyltryptophan, 3-indoxyl sulfate, pseudouridine, and combinations thereof is described. The method comprises subjecting the sample to an ionization source under conditions suitable to produce one or more ions detectable by mass spectrometry from each of the one or more of the analytes; measuring, by mass spectrometry, the amount of the one or more ions from each of the one or more analytes; and using the measured amount of the one or more ions to determine the amount of each of the one or more analytes in the sample. Also described is a kit comprising one or more isotopically labeled analogues as internal standards for each of the one or more analytes.