Table 1: Precision of the determination of 4′-OH-mephenytoin (mean ± SD, ).

Joined concentration (ng/mL)Intraday (ng/mL)RSD (%)Interday (ng/mL)RSD (%)

230 3.75% 4.41%
2300 2.57% 3.40%
5800 2.09% 2.45%