Special Issues-04-01-2006

Column developments in HPLC have benefited protein aqnd peptide separations in a number of ways. More silica based phases and column formats have become available, expanding the use of HPLC for the separation of proteins by different modes of chromatography as well as improving resolution and throughput. Hydrophobic interaction chromatography, immobilized metal affinity chromatography as well as ion Exchange and size exclusion are now practical analytical tools for proteins and peptides. New enrichment columns are benefiting proteomic research.

Chiral separations remain high on the priority list of drug developers. Liquid chromatography and supercritical fluid chromatography continue to vie for dominance in the chiral separation market but might be reaching the state of complementary methodologies. New separation technologies and new advances in current products continue to elevate the state of the art of chiral separations. Automation in both screening for chiral selectivity and preparative purifications has helped make significant gains in productivity in this area.

Although size exclusion chromatography (SEC) is a fairly mature separation technique, improvements are continually made in packing technology. Howard Barth and Greg Saunders review some of the basics of SEC and look at the current status of column technology, including developments for faster and higher resolution size separations.

Ultrahigh-pressure liquid chromatography (UHPLC) is a technique that is experiencing continued growth due to the benefits in separation power and speed of analysis over traditional HPLC. We attempt here to give an overview of some of the advances that have occurred in UHPLC since 2003, from the standpoint of both fundamental research and the introduction of commercially-available technology.

With the advent of column materials that can be used effectively at temperatures well over 100 degrees Celsius, high temperature liquid chromatography (HTLC) separations have gained more attention in the last few years. Advantages of HTLC include fast analysis time, better selectivity, improved column efficiency, and minimization of the use of organic solvents involved in the mobile phase.

The author describes several commercially available novel phases for high performance liquid chromatography separations. Novel phases can provide an alternative and complementary separation for many analyses performed on C8 or C18 columns. Many of the separations discussed in the article could not be accomplished on C8, C18, or even phenyl phases.

Column packing materials continue to evolve as user needs for highthroughput, high-resolution and high-sensitivity HPLC analyses drive further developments. In this introductory article to this supplement, Ron Majors covers basic column packing morphology and particle design and compares and contrasts modern HPLC columns. Some applications of modern HPLC columns are provided. Future directions in packing developments are predicted.

Monoliths are separation media in the format that can be compared to a single large "particle" that does not contain interparticular voids. As a result, all the mobile phase must flow through the stationary phase. This convective flow greatly accelerates the rate of mass transfer. In contrast to diffusion, which is the typical driving force for mass transfer within the pores of particulate stationary phases during chromatographic processes, convective flow through the pores enables a substantial increase in the speed of the separation of large molecules such as proteins. A thorough theoretical treatment of the mass transfer within monolithic materials has been developed by Liapis (1) and Tallarek (2).

Ion exchange is one of the older of the chromatographic techniques yet each year new products continue to hit the market. In this paper, Chris Pohl of Dionex will summarize some of the stationary phases that have been developed for modern ion-exchange and ion chromatography. He will focus on phase design and then turn his attention to new anion and cation columns introduced in the last couple of years.