Determining the plasma 6MP concentration
Blood samples (5ml) were collected in pre-labelled vacutainers containing K3EDTA as anticoagulant at pre-dose (0 h) and 0.08, 0.17, 0.25, 0.33, 0.50, 0.75, 1.00, 1.33, 1.67, 2.00, 2.50, 3.00, 4.00, 5.00, 6.00, 8.00, 10.00, 12.00, 16.00 and 20.00 hours following drug administration in each period. The samples were centrifuged and stored at -80± 8°C at the clinical site until analysis. A validated LC-ESI-MS/MS bioanalytical method was developed for the quantification of 6MP. The calibration curve extended from 1.0 ng/mL to 400.0 ng/mL. The intra- and inter-batch precision (% coefficient of variance [CV]) and mean accuracy (% bias) ranged from 1.75 to 3.85 and -1.69 to 2.13, respectively.