Factorial design for the development of automated solid-phase extraction in the 96-well format for determination of tesaglitazar, in plasma, by liquid chromatography-mass spectrometry.

An analytical method was developed for the determination, in blood plasma, of a novel peroxisome proliferator-activated receptor (PPAR) agonist drug, tesaglitazar. The drug and the isotope labelled internal standard were isolated by solid-phase extraction (SPE) on hexylsilica, separated by reversed-phase liquid chromatography and quantified by tandem mass spectrometry. Factorial design and a robotic sample processor were employed in the exploration and optimisation of the SPE procedure in the 96-well format. This allowed rapid development of the method, notably limiting the process to four experiments before validation. The detectability was greatly improved by utilising the formation of sodium adducts in atmospheric pressure positive ionisation mass spectrometry. Absolute recovery was more than 95% with a coefficient of variation of 5% at a level of 8.7 nM. The accuracy and precision of the automated SPE method presented here matched the excellence of the previously used method based on manual liquid-liquid extraction. Furthermore, the method resulted in an increased sample throughput.