Rapid and sensitive determination of posaconazole in patient plasma by capillary electrophoresis with field-amplified sample stacking.

The high morbidity and mortality associated with invasive fungal infections have increased the importance of improving treatment efficacy. Posaconazole is a novel agent with strong antifungal activity and low toxicity. The success of posaconazole pharmacotherapy strongly depends on precise controlling of concentration of the drug in the blood. In the present study, a solid phase extraction-capillary electrophoresis (SPE-CE) method was developed for rapid and accurate determination of posaconazole in the plasma of patients. We used the field-amplified sample stacking (FASS) technique to improve the sensitivity of CE, and applied the SPE procedures to reduce the matrix effect that was frequently encountered by biological samples in FASS system. Effect of filter types on the recovery rate of compounds with high lipophilicity was carefully investigated. Parameters affecting FASS performance were all optimized to obtain the best sensitivity with the highest speed. When using 1.25 M formic acid as the background electrolyte and 0.2 M formic acid in 95% (v/v) methanol as the sample solution, the limit of detection (LOD) for posaconazole was 10 ngmL(-1), with an analytical run time of less than 5 min. The relative standard deviation (RSD) of the peak area ratios for repeatability (intra-day, n=6) and intermediate precision (inter-day, n=3) were lower than 7.2% and 7.5%, respectively. The accuracy was tested by recovery, and the recovery rates were within 95.1% and 106.4%, respectively. The successful application of the developed method demonstrated its feasibility as an effective method for clinical use.