Evaluating the Effects of Solid‐Phase Cartridge Chemistry on Extraction of Bisphosphonates and ITPP From Equine Plasma

Bisphosphonate drugs and myo-inositol trispyrophosphate are of concern to the racing industry and have been listed as prohibited substances in equine sports. The current bisphosphonate plasma screening analysis employed at the Australian Racing Forensic Laboratory involves the use of sequential solid-phase extraction procedures, passing the samples through a mixed mode cartridge, followed by a weak anion exchange cartridge. The eluates collected following the second extraction are then methylated and analysed by liquid chromatography-mass spectrometry. Under these extraction conditions, some bisphosphonates have shown poor recovery. To improve the extraction efficacy, the effects of cartridge chemistry were evaluated. In particular, the weak anion exchange cartridges used for screening were compared to an affinisep AttractSPE polymeric phase cartridge. The effectiveness of each extraction approach was assessed through both a visual comparison of signal to noise in extracted chromatograms and recovery measurements to determine the best approach for routine screening.