Efficacy of plasma phospholipid removal during sample preparation and subsequent retention under typical UHPLC conditions

Background: Several new products have been marketed with the specific capability of removing phospholipids. These products were evaluated alongside more traditional extraction techniques, using UHPLC and precursor-ion scanning (pre m/z 184), which detects glycerophosphocholines (GPCho), lyso-GPCho and sphingomyelins. Using this technique the plasma GPCho profile of human, dog and rat plasma is briefly compared. Results: Precursor-ion scanning detected more of the phospholipid profile in extracts than a SRM experiment (m/z 184-184). Products designed for the purpose were the most efficient at removing phospholipids and reversed-phase SPE was better than mixed-mode cation exchange. A comparison of different UHPLC columns demonstrated that C-8 or phenyl phases would help manage the elution of GPChos. Conclusion: Phospholipid removal plates are useful where no sample concentration is required; however for more challenging LOD it will be necessary to enrich the original sample. In these cases build-up of phospholipids can be avoided with a thoughtful choice of UHPLC column.