HPLC

This month, John Dolan looks at how changes in retention time can help to identify the source of some LC problems and demonstrates what can be learned from observing how the retention varies.

This column focuses on some of the latest developments in preparative-scale columns, bulk packing materials and column hardware designs. Silica, polymeric and other packings are discussed together with the newest monolithic columns.

In this month's column, John Dolan reveals a number of simple and useful shortcuts or rules of thumb that he has acquired over the years that allow quick estimates to guide method development or help solve a problem.

In this month's column the authors present a case study to outline several gradient quality checks that can be performed periodically to ensure proper performance of LC instrumentation. The example shows how by taking the time to perform such tests, potential problems can be identified before they reach a critical point.

In this article, the authors present a column ranking system to facilitate column selection in reversed-phase liquid chromatographic analysis. The system ranks columns based on their similarity to a reference column of choice and its applicability to a real pharmaceutical analysis is demonstrated.

Just how good are your gradients?

Column Editor Ron Majors turns his attention to preparative chromatography. He focuses on the columns used in preparative chromatography, including how to select the appropriate mode, mobile-phase system and operating conditions.

Are you guilty of strange troubleshooting and maintenance habits that have been passed on to you from predecessors? John Dolan looks at some such practices, which were once acceptable, but don’t make sense in today’s lab.

In this article the authors review the use of elevated temperatures in HPLC, and provide examples covering separations of both small molecules and biomolecules. Generic issues of temperature dependence of retention and plate height are discussed, and comparisons are made between temperature gradient and solvent gradient elution. They describe how the use of elevated temperatures allow good chromatographic efficiency to be obtained at flow-rates higher than those optimal at ambient temperature, thus increasing the speed of separation.

Column author, John Dolan, presents a simple but powerful isolation technique for identifying problems with LC methods and equipment.

The authors use the stochastic model to estimate the fundamental characteristics of the separation process.

A C18 stationary phase based upon a titanized silica support was prepared through reaction with octadecyltrimethoxysilane.

A look at the latest developments in preparative-scale columns, bulk packing materials, and column hardware designs.

The author focuses on a simple but powerful tool for isolating problems in the laboratory.

The separation of individual congeners of commonly used fluorescent whitening agents is described.

The authors study the solubility of five buffers commonly used in reversed-phase liquid chromatography.

In this month's column, John Dolan addresses some of the guidelines regarding system suitability tests and comments on their significance for those developing chromatographic methods.

The authors discuss the application of shear-driven chromatography, a technique that depends on viscous drag to propel mobile phase in high-resolution/high-speed liquid chromatography. This method, it is claimed, overcomes the pressure- and voltage-drop limitations of both HPLC and CEC. Early development of the technique is reviewed and updated with the current status of the group's work. Also covered are the challenges faced and opportunities available to interface such systems to MS and UV/vis absorption detectors.

In this month's instalment, the authors cover the topics of column-switching techniques and parallel chromatography for LC?MS?MS methods, and describe the time benefits that can be achieved using such systems. An example set-up is presented and the authors outline the various steps required to perform such analyses routinely.

Sounds simple, but what is required?

A simple, rapid, and sensitive method is presented for clinical measurements of ascorbic acid and malondialdehyde in human serum.