Table 1. The limits of detection (LODs) of 8 canonical NTPs with and without 8-DMQ labeling by LC-ESI-MS/MS analysis under the optimized detection conditions.

Analytes	Unlabeled (LODs, fmol)	After labelling (LODs, fmol)	Detection limit improved (folds)
ATP	33.6	0.6	56
GTP	46.2	0.6	77
CTP	104.0	1.3	80
UTP	411.0	3.0	137
dATP	17.2	0.4	43
dGTP	124.3	1.1	113
dCTP	58.2	0.6	97
TTP	44.5	0.5	89