Table 2. Linearity of the UPLC-MS/MS method for ifosfamide quantification in DBS with 30 and 45% HTC.
| N | Ifosfamide concentration (ng/mL) with 30% HTC | ||||||
| LLQ (100) | 500 | 1000 | 2500 | 5000 | 7500 | 10000 | |
| 1 | 94.9 | 521.3 | 972.1 | 2723.9 | 4588.06 | 7500.2 | 10190.1 |
| 2 | 100.4 | 500.8 | 997.5 | 2594.5 | 4722.2 | 7397.3 | 10293.1 |
| 3 | 95.5 | 545.6 | 1008.4 | 2461.8 | 4553.8 | 7605.3 | 10312.3 |
| Mean ± SD | 96.9±3.0 | 522.5±22.4 | 992.6±18.6 | 2593.4±131.0 | 4621.3±89.0 | 7500.9±104.0 | 10265.1±65.7 |
| % CV | 3.1 | 4.2 | 1.8 | 5.0 | 1.9 | 1.3 | 0.6 |
| % Deviation | 3.0 | -4.5 | 0.7 | -3.7 | 7.5 | -0.01 | -2.6 |
| Ifosfamide concentration (ng/mL) with 45% HTC | |||||||
| 1 | 97.6 | 517.0 | 1042.1 | 2325.1 | 5247.9 | 7231.9 | 10139.3 |
| 2 | 94.5 | 494.8 | 1066.0 | 2483.2 | 5266.2 | 7190.9 | 10004.9 |
| 3 | 97.2 | 491.3 | 1035.5 | 2573.0 | 5373.5 | 7368.8 | 9761.1 |
| Mean ± SD | 96.4±1.6 | 501.0±13.9 | 1047.8±16 | 2460.4±125.5 | 5295.8±63.8 | 7263.8±93.1 | 9968.4±197.7 |
| % CV | 1.7 | 2.7 | 1.5 | 5.1 | 1.2 | 1.2 | 1.9 |
| % Deviation | 3.5 | -0.2 | -4.7 | 1.5 | -5.9 | 3.1 | 0.3 |
SD: Standard Deviation; % CV: Coefficient of Variation = (standard deviation/mean)*100; % Deviation was calculated as: (theoretical concentration minus calculated concentration/theoretical concentration)*100 [6]. Linearity of 30% HTC: Y = 0.5325X + 171.58 (r2 = 0.9958) and for 45% HTC: Y = 0.6488X + 88.33 (r2 = 0.9968).