ARTICLES

Simultaneous Determination of Paraxanthines and Cotinine in Human Plasma by Solid-Phase Extraction Followed by LC–MS–MS
Rossana Bossi and Bodil Hammer Bech
A multi-residue method has been developed and validated for the analysis of paraxanthines (caffeine and its metabolites) and cotinine in human plasma. The method involves off-line solid-phase extraction (SPE) and analysis by liquid chromatography coupled to tandem mass spectrometry LC–MS–MS with electrospray ionization (ESI) in positive mode (PI). The developed and validated method was fast, selective, and convenient for the simultaneous determination of cotinine, caffeine, and its metabolites in human plasma. The method has been successfully applied to the analysis of 500 samples from pregnant women in a clinical study.

Quality by Design in Pharmaceutical Analysis Using Computer Simulation with UHPLC
Róbert Kormány, Imre Molnár, and Jenő Fekete
In this study, the quality-by-design principle is applied instead of trial-and-error in the development of a liquid chromatography method. With few measurements, the appropriate stationary phase and chromatographic conditions such as the composition of mobile phase, gradient time, temperature, and pH can be determined. A mixture of an active pharmaceutical ingredient and its 13 impurities was analyzed on a short narrow-bore column (50 mm × 2.1 mm, packed with sub-2-µm particles) providing short analysis times. The performance of commercial modeling software for robustness testing was systematically compared to experimental measurements and design-of-experiment–based predictions.

COLUMNS

Column Watch
New Chromatography Columns and Accessories at Pittcon 2014 (Part 2)
Ronald E.  Majors
Part 2 of our yearly report on new products introduced at Pittcon. This month gas chromatography columns, sample preparation, and chromatographic and sample preparation including small benchtop instruments will be covered.

LC Troubleshooting
Readers’ Questions: Calibration
John W. Dolan
This month’s LC Troubleshooting looks at two reader-submitted questions regarding method calibration.

GC Connections
New Gas Chromatography Products 2014
John V. Hinshaw
John Hinshaw presents his annual review of new developments in the field of gas chromatography seen at Pittcon and other venues in the past 12 months.

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The May issue will also be accompanied by a special supplement: "Recent Developments in Sample Preparation"