Analysis of Sphingosine and Sphinganine from the Aqueous Humor for Signaling Studies Using Ultrahigh-Performance Liquid Chromatography-Mass Spectrometry

Sphingolipids, including sphingosine and sphinganine, are one of the major classes of lipids. They serve as constituents of cell membranes and lipid rafts and aid in the performance of cell-cell communication and adhesion. Abnormal levels of sphingolipids in the aqueous humor can indicate impaired sphingolipid metabolism and associated ocular pathologies. Sphingolipids can be extracted from the aqueous humor by the methyl-tert-butyl ether (MTBE) lipid extraction method and subsequently analyzed by liquid chromatography-mass spectrometry (LC-MS). This chapter describes a modified protocol for an MTBE lipid extraction from the aqueous humor, followed by analysis with ultrahigh-performance liquid chromatography-mass spectrometry (UHPLC-MS).

High-performance enantiomer separation of nonsteroidal anti-inflammatory drugs (NSAIDs) by 3 μm reversed-phase chiral columns and application to the optical purity testing of naproxen drug substances and its formulations

The enantiomer separation of five nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen, ketoprofen (KP) and naproxen (NX), which are included in The Japanese Pharmacopoeia 16th edition (JP16), was investigated by employing four kinds of 3 μm reversed-phase chiral columns (AD-3R, AS-3R, OD-3R and OJ-3R). Except for KP, the enantiomers of four NSAIDs were successfully separated by one of the four columns. Among five NSAIDs, only NX has been used as a single enantiomer (S-form, active form) in the clinical field (JP16); therefore, optical purity testing method of NX is required for its quality evaluation. Among four CSPs, the method was developed by using an AS-3R column, which showed good enantioselectivity for NX enantiomers. By optimizing the conditions, the resolution (Rs) of 2.55 was obtained for NX enantiomers within approximately 6 min. The minor enantiomer R-form eluted before the main active enantiomer S-form. Finally, the developed method was applied to the optical purity testing of NX active pharmaceutical ingredients (APIs), and its formulations (tablet and capsule). Other than the minor enantiomer (R-form, inactive form, 0.21 - 0.78%), normal (not chiral) impurities at levels of 0.01-0.3% were simultaneously separated and determined by the method, showing an excellent separation capability of the method for those impurities including the minor enantiomer. The content uniformity test of the NX tablet according to JP16 was also successfully performed by the method with the AS-3R column. Normal phase separation with two chiral columns (AD-H and OD-H) and capillary electrophoretic (CE) separation were also investigated for five NSAIDs enantiomers to discuss the enantioselectivity.