Table 3. Intraday repeatability and inter-day reproducibility of assays.
| Intraday | Inter-day | |||||||||||
| Day 1 | Day 2 | Day 3 | ||||||||||
| Measured concentration (μmol/L) |
RSD (%) |
Measured concentration (μmol/L) |
RSD (%) |
Measured concentration (μmol/L) |
RSD (%) |
Measured concentration (μmol/L) |
RSD (%) |
|||||
| Nτ-Methylhistidine | ||||||||||||
| LC–MS/MS (m/z 170.20>96.10) |
12.64 | 5.97 | 11.34 | 4.66 | 12.11 | 3.13 | 11.84 | 1.45 | ||||
| LC–MS/MS (m/z 170.20>124.10) |
12.25 | 5.44 | 11.60 | 6.93 | 12.00 | 4.37 | 11.95 | 1.17 | ||||
| UHPLC | 10.37 | 4.21 | 10.80 | 3.86 | 9.80 | 4.95 | 10.32 | 5.77 | ||||
| Nπ-Methylhistidine | ||||||||||||
| LC–MS/MS (m/z 170.20>96.10) |
7.99 | 9.83 | 7.69 | 6.52 | 8.37 | 9.68 | 8.01 | 2.14 | ||||
Intraday and inter-day repeatability was measured as the mean value of six and three replicates, respectively. RSD (%) = (standard deviation / measured mean value) × 100.