Strategies on efficient method development of on-line extraction assays for determination of MK-0974 in human plasma and urine using turbulent-flow chromatography and tandem mass spectrometry

On-line extraction assays using cohesive high-turbulence liquid chromatography (HTLC) coupled with tandem mass spectrometer (MS/MS) have been developed for the determination of MK-0974 in human plasma and urine. In this report, a four-step strategy for efficient method development of an on-line extraction assay was discussed. Several challenges – namely extraction recovery, carryover and analyte loss to urine container – were addressed. The assay procedures included sample preparation on a Packard MultiPROBE II liquid-handling system, direct injection on a Cohesive Flux 2300 system, on-line extraction with a Cohesive C18 column (0.5 mm × 50 mm, 50 μm), HPLC separation on a FluophasePFP column (50 mm × 3 mm, 5 μm) under cohesive quick-elution mode and MS detection on a Sciex API4000 in multiple-reaction monitoring (MRM) mode using positive ionization and turbo ion-spray. Since 37–80% analyte loss was observed in urine QCs, 1% BSA was added to bring urine QC accuracy back to ∼100% of nominal. Because of the nature of BSA, the urine assay was established by adapting the plasma method. Thus, the two assays were able to be validated side-by-side, which reduced the validation time by approximately two-fold. The linear dynamic ranges were 0.5–500 and 1–1000 nM for the plasma and urine assays, respectively. Obtained from five standard curves constructed with five lots of human plasma or urine, the intra-day precision (%CV) was <3.14 and <2.62%, and the accuracy was 98.3–101.0 and 99.13–100.64% of nominal for plasma and urine assays, respectively. Both plasma and urine QC samples were stable when kept at room temperature for 4 h, at −70 °C for 3 weeks, or after three freeze–thaw cycles. Both assays gave reasonable relative recovery (>88.8%) and acceptable matrix effect (<15%). The carryover from the upper limit of quantification (ULOQ) was able to be controlled at <20% of lower limit of quantification (LLOQ).