Fig. 2.

Representative MRM chromatograms of RIF (I) and RPT (II, IS) in: (A) a blank human plasma sample; (B) a blank human plasma sample spiked with RIF at the LLOQ of 25 ng/mL; (C) patient plasma sample 25 h after an oral dose of 10 mg/kg (RIF concentration; 31 ng/mL); (D) CSF sample from a patient receiving a 10 mg/kg daily oral dose of RIF (RIF concentration; 41.83 ng/mL). Sample preparation for 100 μl of (B)–(D) was performed using 300 μl of 50/50 ACN/methanol (including 250 ng/mL IS), whereas IS was not included in case of (A).