The mean slope of the detector response vs concentration curve was 3301401 (±81242); RSD 2,46%%. mean coefficient of determination (R 2 ) 0.9994 (±0,0004). The equation of the curve "mean back-calculated concentration vs nominal concentration" was y = 0,9966x + 0,0565 (R² = 1). For intermediate precision, the RSD was less than 6%, and accuracy was between 96 and 102%, exceptions being on day two of the study when recovery was 87% and 112% for the first and third calibration points, respectively. The mean slope of the detector response vs concentration curve was 3250083 (± 121928. RSD, 3.75% with a coefficient of determination (R 2 ) of 0,9986 (±0,0016). The equation of the mean back-calculated vs nominal concentration was y = 0,9941x + 0,2519 (R² = 0,9996). The equivalent values for the UPLC-MS method are mean overall RSD 3,96% (repeatability) and 2.69 % (intermediate precision), and for the UPLC-UV method, 2.88 % and.2.15%, respectively (supplemental tables S1 and S2, respectively). The proximity of the results between the three methods was evaluated by ANOVA; as may be seen in supplemental table S3, the difference in back calculated concentrations among the three methods was not significant.