Risk assessment of diabetes mellitus using dried saliva spot followed by ultra-performance liquid chromatography with fluorescence and mass spectrometry

Abstract The dried saliva spot (DSS) seems to be a convenient sampling technique for bioanalysis. In our previous research, the DSS sampling was used for the determination of dl -lactic acid (DL-LA) and the D/L ratio of diabetic, pre-diabetic and healthy persons. However, the method required an expensive tandem MS/MS apparatus to obtain a highly sensitive detection. To avoid the use of such instrument, this paper proposes cheaper determination systems by ultra-performance liquid chromatography (UPLC) with fluorescence (FLR) and/or single mass spectrometry (MS). The carboxylic acids including DL-LA in the DSS were labeled with a chiral fluorescence reagent, (S)(+)-4-nitro-7-(3-aminopyrrolidin-1-yl)-2,1,3-benzoxadiazole (NBD-(S)(+)-APy), and determined by UPLC-FLR-MS. The limits of detection of LA by FLR and MS were approximately 1.0 μM (0.1 pmol) and 0.20 μM (0.02 pmol), respectively, whereas the limits of quantification were 5.0 μM (0.5 pmol) by FLR and 1.0 μM (0.1 pmol) by MS. The proposed DSS method was used for the determination of the enantiomers of LA of diabetic, pre-diabetic and healthy persons. The D/L-LA ratios obtained from the FLR were correlated with those of MS, although the ratios of the FLR were slightly lower than those of MS. Furthermore, the D/L-LA ratios of the present FLR or single MS were well correlated with those of the tandem MS/MS obtained from our previous study. The results indicated that the UPLC-FLR-MS was alterable to the previous UPLC-MS/MS method. Consequently, the proposed UPLC-FLR and/or UPLC-MS seem to be applicable as a cheaper screening method for diabetes mellitus using the DSS sampling.