. Author manuscript; available in PMC: 2018 Sep 10.

Published in final edited form as: J Chromatogr B Analyt Technol Biomed Life Sci. 2015 Oct 31;1006:167–178. doi: 10.1016/j.jchromb.2015.10.030

Table 3.

Matrix effect of isotope-labeled NTPs and dNTPs from cell pellets (with ~1 million cells)

	Setl curve^a	Set2 curve^a	Matrix factor^b
ATP	A=2822C – 2821, R²= 0.998	A=2394C – 1622, R²= 0.999	0.85
CTP	A=14308C – 15077, R²= 0.999	A=11335C – 24583, R²=0.999	0.79
GTP	A=11233C – 11401, R² = 0.998	A=10441C – 20729, R²=0.999	0.93
UTP	A=6977C – 3371, R²=0.999	A=5015C – 7256, R²=0.999	0.72
dATP	A=10957C – 1951, R²=0.999	A=9587C – 14755, R²=0.999	0.88
dCTP	A=7535C – 3241, R²=0.998	A=5761C – 5377, R²=0.999	0.76
dGTP	A=1528C – 3667, R²=0.998	A=1448C – 2030, R²=0.999	0.95
dTTP	A=7196C ± 2428, R²=0.998	A=5741C – 8465, R²=0.999	0.80

Two sets of calibration standards (at the final concentrations of 10, 25, 50, 100, 250, and 500 nM) were prepared by spiking 10 μL of the working solution of isotople-labeled standard mix into 90 μL of mobile phase A solution (set 1), or 90 μL of post-extracted cell matrix that was prepared from a cell sample with ~ 1 million cells (set 2). Set 1 and 2 calibration standards were directly subjected to the LC-MS/MS analysis.

The matrix factor was calculated as the slope ratio of the calibration curve prepared in post-extracted cell matrix (Set 2) to that in mobile phase A solution (Set 1). Matrix factor within 0.85 – 1.15 indicates no apparent matrix effect; matrix factor < 0.85 indicates ion suppression; and matrix factor > 1.15 indicates ion enhancement.