Conclusions
The described LC-MS/MS methods allow for the measurement of total and free cefazolin in both plasma and cord blood.
Methods
Specimen preparation for the measurement of total cefazolin was performed via protein precipitation with acetonitrile containing the internal standard cloxacillin. Ultrafiltration was used to isolate free cefazolin. Processed samples were analyzed on a Prelude SPLC system coupled to a TSQ triple quadrupole Vantage mass spectrometer. Methods were validated following FDA bioanalytical guidelines.
Results
The analytical measuring ranges of these methods were 0.48-480 µg/mL and 0.048-48 µg/mL for total and free drug, respectively. Calibration curves were generated using 1/x2 weighted linear regression analysis. Total cefazolin demonstrated inter- and intra-assay precision of ≤20% at the LLOQ and ≤11.2% at other levels. Free cefazolin demonstrated inter- and intra-assay precision of ≤18.5% at the LLOQ and ≤12.6% at other levels, respectively. Accuracy (%DEV), carryover, matrix effects, recovery and stability studies were also acceptable based on FDA recommendations. Furthermore, it was demonstrated that samples prepared in cord blood can be accurately quantified from an adult plasma calibration curve, with recoveries ≤9.1% DIF and ≤11.9% DIF for total and free cefazolin, respectively. Conclusions: The described LC-MS/MS methods allow for the measurement of total and free cefazolin in both plasma and cord blood.