Improved hydrophobic subtraction model of reversed-phase liquid chromatography selectivity based on a large dataset with a focus on isomer selectivity.

Reversed-phase (RP) liquid chromatography is an important tool for the characterization of materials and products in the pharmaceutical industry. Method development is still challenging in this application space, particularly when dealing with closely-related compounds. Models of chromatographic selectivity are useful for predicting which columns out of the hundreds that are available are likely to have very similar, or different, selectivity for the application at hand.

Continuous stationary phase gradient preparation on planar chromatographic media using vapor phase deposition of silane.

A new, versatile, and straightforward vapor phase deposition (VPD) approach was used to prepare continuous stationary phase gradients (cSPGs) on silica thin-layer chromatography (TLC) plates using phenyldimethylchlorosilane (PDCS) as a precursor. A mixture of paraffin oil and PDCS was placed at the bottom of an open-ended rectangular chamber, allowing the reactive silanes to evaporate and freely diffuse under a controlled atmosphere. As the volatile silane diffused across the length of the TLC plate, it reacted with the surface silanol groups thus functionalizing the surface in a gradient fashion.

Preparation and characterization of stationary phase gradients on C8 liquid chromatography columns.

Continuous C8 stationary phase gradients are created on commercial Waters Symmetry Shield RP8 columns by strategically cleaving the C8 moieties in a time-dependent fashion. The method relies on the controlled infusion of a trifluoroacetic acid/water/acetonitrile solution through the column to cleave the organic functionality (e.g.

Experimental design and re-parameterization of the Neue-Kuss model for accurate and precise prediction of isocratic retention factors from gradient measurements in reversed phase liquid chromatography.

The present work describes a re-parameterization of the Neue Kuss (NK) model for describing retention in liquid chromatography, and this re-parameterized model is used to fit a large set of isocratic retention measurements with improved convergence properties relative to the original parameterization of the model. Next, an experimental design for retention measurements using mobile phase gradient elution conditions is proposed for the purpose of obtaining accurate and precise NK parameters. Simulated retention data for mobile phase gradient elution conditions with two different levels of noise, as well as an essentially zero noise level were fit with the re-parameterized model.

Characterization of a high throughput approach for large scale retention measurement in liquid chromatography.

Many contemporary challenges in liquid chromatography-such as the need for "smarter" method development tools, and deeper understanding of chromatographic phenomena-could be addressed more efficiently and effectively with larger volumes of experimental retention data than are available. The paucity of publicly accessible, high-quality measurements needed for the development of retention models and simulation tools has largely been due to the high cost in time and resources associated with traditional retention measurement approaches. Recently we described an approach to improve the throughput of such measurements by using very short columns (typically 5 mm), while maintaining measurement accuracy.