Evaluation of automated micro solid phase extraction tips (μ-SPE) for the validation of a LC–MS/MS bioanalytical method

Automated μ-SPE tips were successfully utilized for the determination of posaconazole in rat plasma. The bioanalytical method using μ-SPE tips was successfully qualified for routine quantitation of posaconazole over the concentration range of 10.0–10,000 ng/mL in rat EDTA plasma. Inter-assay precision, based on percent relative deviation for n = 18 replicate quality controls, was ≤5.7%. Inter-assay accuracy based on n = 18 replicate quality controls was ±7.7%. Complete solid phase extraction using μ-SPE tips was demonstrated on a Tomtec liquid handler where >95% recovery for posaconazole was obtained. The μ-SPE tips had sufficient capacity to extract at least 100 μL plasma fortified with 10 μg/mL of posaconazole and the analyte could be efficiently eluted with as little as 60 μL of methanol. Of particular note is the unique ability of these μ-SPE tips to perform exhaustive solid phase extraction more commonly performed when using liquid/liquid extraction.