Table 3.
Accuracy and precision of the approach for relative quantification using LC-MS and 18O labeling as determined by measuring three replicates of 
mixtures prepared at the heavy-to-light ratios noted
| Expected | Measured | CV (%) | |
|---|---|---|---|
| 5′-[m5U]ΨCGp-3′ | |||
| [M-H]− (m/z 1293.16) | 0.20 | 0.187 ± 0.0045 | 2.38 |
| 1.00 | 1.11 ± 0.029 | 2.61 | |
| 5.00 | 5.13 ± 0.0395 | 0.769 | |
| 10.00 | 9.16 ± 0.341 | 3.72 | |
| [M-2H]2- (m/z 646.074) | 0.20 | 0.141 ± 0.0266 | 18.8 |
| 1.00 | 1.09 ± 0.0249 | 2.28 | |
| 5.00 | 5.50 ± 0.142 | 2.58 | |
| 10.00 | 9.76 ± 0.370 | 3.79 | |
| 5′-A[s4U]UAGp-3′ | |||
| [M-H]− (m/z 1648.18) | 0.20 | 0.113 ± 0.0146 | 13.0 |
| 1.00 | 0.991 ± 0.130 | 13.1 | |
| 5.00 | 4.56 ± 0.285 | 6.24 | |
| 10.00 | 10.05 ± 0.919 | 9.14 | |
| [M-2H]2- (m/z 823.587) | 0.20 | 0.117 ± 0.00639 | 5.48 |
| 1.00 | 0.959 ± 0.0525 | 5.47 | |
| 5.00 | 4.96 ± 0.336 | 6.78 | |
| 10.00 | 9.21 ± 0.341 | 3.70 |
Quantification was done using the RNase T1 digestion products 5′-[m5U]ΨCGp-3′ and 5′-A[s4U]UAGp-3′, which were found to yield linear and consistent results. CV, coefficients of variation.