Minimizing matrix effects while preserving throughput in LC–MS/MS bioanalysis

Background: Phospholipids are known to cause matrix effects in LC–MS analysis and are not effectively removed by one of the most common method of sample preparation: organic solvent protein precipitation. The objective of this research is to minimize phospholipid interferences chromatographically. Results: In this article we examine several chromatographic approaches and highlight the method we developed that allows for the rapid gradient separation of model drug molecules from phospholipids. Conclusion: The new approach (which utilizes a mixture of methanol and acetonitrile as the organic mobile phase on a 2.1 × 20 mm C18 column) minimized phospholipids-related matrix effects in the analysis of plasma samples prepared by protein precipitation and is suitable for high-throughput bioanalysis in drug discovery.

Chromatography with higher pressure, smaller particles and higher temperature: a bioanalytical perspective

Recent years have seen widespread use of ultra-high-pressure liquid chromatography (UHPLC) in biological fluids. Most commonly the emphasis is on developing high throughput assay methods to reduce the analysis time and cost. Particle size and temperature are chromatographic parameters that can be changed to improve efficiency and obtain rapid separations. UHPLC and high-temperature liquid chromatography (HTLC) are two techniques that reduce the analysis time by decreasing the size of the column packing material and increasing the column temperature, respectively. Both of these techniques have advantages and limitations. In this article we have summarized the history, theoretical background of UHPLC and HTLC and the various advantages and limitations of sample preparation techniques and the detection systems (mass spectrometry and ultraviolet) used for the bioanalytical assays. In addition, selected bioanalytical applications of the two techniques have been reviewed and tabulated.

Determination of naproxen using DBS: evaluation & pharmacokinetic comparison of human plasma versus human blood DBS

Background: Dried blood spots (DBS) sampling is a well-known technology for qualitative determination such as DNA analysis and screening of newborn metabolic disorders. The scientific community has recently expressed interest in applying the DBS technique for quantitative determination of drugs in biological fluid. Results: Two new bioanalytical assays were developed and validated for the determination of naproxen in human plasma and in DBS samples using liquid chromatography coupled with tandem MS. Furthermore, plasma and DBS clinical samples were collected from four subjects enrolled as part of a bioequivalence study. Concentration data for plasma and DBS samples were determined and pharmacokinetic (PK) profiles in plasma and in DBS samples were compared. Conclusions: A strong correlation between PK data obtained by the DBS and conventional plasma method was observed, which makes DBS a valuable technique for further naproxen bioavailability and PK investigations and studies.

Elimination of LC–MS/MS matrix effect due to phospholipids using specific solid-phase extraction elution conditions

Background: The objective is to find elution conditions using different solid-phase extraction chemistries to reduce the amount of phospholipids in plasma extract, which is associated with matrix effect in LC–MS. Results: Phospholipids’ recovery was reduced by decreasing the eluents’ methanol content applied to silica-based and polymer-based reversed-phase solid-phase extraction cartridges while 100% acetonitrile applied to the silica-based cartridges drastically minimized the phospholipids’ elution. Silanol interactions are involved in the increased retention of phospholipids with silica-based reversed-phase cartridges when using high percentages of ACN in eluents. The bioanalytical usefulness of these findings was confirmed by successful extraction recovery of pharmaceutical compounds. Conclusion: Combinations of specific eluents and reversed-phase solid-phase extraction cartridges were found to prevent matrix effect due to phospholipids.