Liquid Chromatography (LC/HPLC)

Two solutions to the problem of obtaining quantitative information about protein expression are to couple two or more chromatographic modes to increase resolution and to use affinity selection techniques.

Tim Wehr looks at the requirements of multidimensional LC and provides examples of some systems used in proteomics.

Tim Wehr looks at the use of fast LC}MS for high-throughput analysis of pharmaceutical compounds.

This month Tim Wehr discusses traditional approaches to protein characterization.

The authors investigated the analytical capabilities of quadrupole, time-of-flight, and Fourier transform mass analyzers for liquid chromatography electrospray mass spectrometry (LC-MS) applications.

How can you avoid phase collapse when 5% organic solvent is too strong?

This month's "Column Watch" describes moving bed chromatography and how the concept is realized in the form of simulated moving bed chromatography. Also included is an inside look at instrumentation, method development, and applications for industrial purifications.

How can internal LC surfaces be made less reactive?

This installment of "Milestones in Chromatography" looks at two major international meetings held in Las Vegas, Nevada, and Seattle, Washington, that were pivotal in the early development of HPLC.

This month's "Directions in Discovery" gives a brief overview of turbulent- flow liquid chromatography, a technique for fast separations. Two examples demonstrate the use of the technology for high-throughput bioanalytical separations in drug discovery.

Given the increasing number of chiral samples and the time constraints under which chromatographers work, choosing an appropriate chiral stationary phase for the resolution of enantiomers can be challenging. In this article, the authors describe a screening approach for chiral HPLC method development.

Stainless steel is inert – or is it?

This month's "Column Watch" examines developments in column packings. Ron Majors looks at the physical design of packing materials from a performance standpoint and discusses some new packing materials that have unique characteristics.

A scouting gradient is a separation run under a standardized set of conditions and can be used to determine the complexity of a sample and estimate the difficulty of the separation. John Dolan tells why he believes using a scouting gradient is the best way to begin method development.

This "Data File" column shows readers how to incorporate e-mail in chromatography data systems and suggests how other Internet technologies can improve modern laboratory practices.

During the past five years, many manufacturers of HPLC columns have focused on improving stationary phase stability and reproducibility. In this study, the authors use a variety of test solutes to compare the efficiency, selectivity, and hydrophobic retention mechanisms of five commercially available HPLC columns based silica, alumina, zirconia, and polystyrene cross-linked with divinylbenzene as the support.

Concluding a two-part series, Ron Majors looks at the trends in the introduction of columns and column-related products at Pittcon 2000. In this second part, he describes gas chromatography and supercritical fluid chromatography columns, CE capillaries, thin-layer chromatography products, sample preparation products, and accessories for chromatography and sample preparation.

After exploiting the chemical factors in the separation process, chromatographers can adjust column conditions – flow rate, column size, and particle diameter – to further improve separations.

This month's "Directions in Discovery" looks at column and mobile-phase selection as well as system components and modification. Making the right choices among these parameters will help analysts get the most out of their liquid chromatography–mass spectrometry systems.

This month's column begins our annual roundup of new column technologies shown at the Pittsburgh Conference. In part I, we'll look at HPLC columns and packings for reversed-, normal-, and bonded-phase; ion-exchange; ion; size-exclusion; and large- and preparative-scale chromatography as well as specialty columns.

In part III of this column series, John Dolan demonstrated that systematic variation of the solvent strength can change selectivity and retention, and changing solvent type can amplify the effect. This month, he looks at three additional parameters (pH, temperature, and column type) for adjusting selectivity.

The efficiencies of microbore-2 columns, which are prepared from blanks that have a wide variety of inner surface roughness, drop sharply when the size of individual surface roughness features approaches the particle size of the packing material. The results suggest that two categories of packed column structure relate to the surface features and yield high and low efficiency columns. This installment of "Column Watch" discusses this conclusion in terms of the stability of an agglomerated layer of packing particles on the blank wall when subjected to shear forces during column packing.

Adapting the organic solvent strength and type can be an effective way to improve an isocratic separation.

The authors investigated the two most popular types of interfaces for benchtop LC–MS systems – the particle interface and the atmospheric-pressure ionization interface – to learn how the information obtained separately from the two can be complementary.

In the second installment of this series, the author looks at the first phase of the life cycle of a new chromatography system, bringing together a number of elements of the workflow and the functions as they are used in the laboratory.