Research Article
Development and Validation of an LC-MS/MS Method and Comparison with a GC-MS Method to Measure Phenytoin in Human Brain Dialysate, Blood, and Saliva
Table 2
Comparison of the GC-MS [
8] versus LC-MS/MS method.
| Criterion | GC-MS | LC-MS/MS |
| Retention time | PHT 15.12 min, IS MPPH 16.15 min | PHT and PHT-D10 2.8 min | Selectivity/sensitivity (absence of PHT) | Good peak differentiation and quantification of PHT. All blank samples were negative (no presence of PHT) | All blank samples were negative (no presence of PHT) | Recovery | 94.1% for QC2 (100 ng/mL) | 89.5% for QC1 (10 ng/mL) | 94.3% for QC5 (1000 ng/mL) | 97.1% for QC3 (1600 ng/mL) | LOD (calculated as S/N ratio of 4 : 1) | 15 ng/mL | <1 ng/mL | LOQ (calculated as 5 times the response/blank) | 50 ng/mL | 10 ng/mL | Accuracy | The calibrator values showed min–max percent deviations of 1–20% for Cal 1 (50 ng/mL) to Cal 6 (1200 ng/mL) | The calibrator values showed min–max percent deviations of 1–8% for Cal 1 (10 ng/mL) to Cal 8 (2000 ng/mL) | Regression coefficient, r2 | r2blood = 0.998 (n = 2) r2dialysate = 0.999 (n = 8) r2saliva = 0.999 (n = 2) | r2blood = 0. 996 (n = 3) r2dialysate = 0.997 (n = 6) r2saliva = 0.995 (n = 3) | Calibration range | 50–1200 ng/mL | 10–2000 ng/mL | Run time per analysis | 30 min | 7 min | Injection volume of the sample | 2.0 µL | 10 µL | Sample preparation time | 5 h for 25 samples | 6 h for 182 samples | Stability of the processed samples | Dried extracts were stable for ≥4 weeks (min/max deviation 4%). No effect by reinjection and storage (33 h) on the autosampler | Reinjection after 7 days showed no difference in accuracy | Sample volume needed | 50 µL | 25 µL |
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