Phospholipid removal combined with a semi-automated 96-well SPE application for determination of budesonide in human plasma with LC–MS/MS

• We have designed a streamlined and effective LC–MS/MS method for quantification of budesonide in human plasma.
• Our method was successfully applied in a pharmacokinetic study and fulfilled the high demands of a low measuring range and a time constraint schedule.
• The method has a unique design that addressed the need for phospholipid removal in order to reduce influence from matrix

A semi-automated method for quantification of budesonide in human plasma was developed, validated, and applied for high-volume analysis of samples in connection with a pharmacokinetic study. Protein and phospholipid removal was performed using an Ostro 96-well filter plate and subsequently combined with C18 solid-phase extraction on a Hamilton Microlab STARlet automation robot. The final extracts were evaporated to dryness and redissolved in 20% acetonitrile/water. The procedure used budesonide-d8 as internal standard and gave a 3.5-fold concentration of plasma to extract. The final extracts (5 μL injected) were analyzed with selected reaction monitoring liquid chromatography–tandem mass spectrometry (LC–MS/MS) using electrospray ionization in positive mode. The chromatography system used a 100 mm ACQUITY BEH UPLC column and a gradient system consisting of aqueous 0.1% formic acid and acetonitrile as organic modifier. Phospholipid removal was found to be needed during method development in order to reduce ion suppression effects from matrix and to increase method sensitivity. The measuring range was 50–5000 pg/mL with and LOD 24 pg/mL. Calibration response showed good linearity (correlation coefficients < 0.99) over the measuring range. The absolute recovery over the sample preparation procedure was estimated to 67%. Total imprecision was <9% at three levels and accuracy was between 98.9 and 103%. The method was successfully applied for analysis of 864 study samples in a short time. The quality control samples at concentration levels 200 and 2000 pg/mL gave a total imprecision of 7.4% and 4.2%, respectively, (n = 95).