Highlights of HPLC 2014

Jul 01, 2014

HPLC 2014 was held May 11–15 in New Orleans, Louisiana, for the first time and much earlier than normal. This installment of "Column Watch" covers some of the technology and application advances presented at HPLC 2014. We review the overall liquid-phase chromatographic trends, summarize the awards presented, and discuss the column technology highlights observed at the symposium.

The 41st International Symposium on High Performance Liquid Phase Separations and Related Techniques, which alternates between Europe and North America, with occasional side meetings in Australia and Asia, was held May 11–15 in New Orleans, Louisiana — its first time in the southern part of the United States. More affectionately known as HPLC 2014, the symposium is the premier scientific event for bringing together the myriad techniques related to separations in liquid and supercritical fluid media. Chaired by Professor J. Michael Ramsey of the University of North Carolina at Chapel Hill, with the able assistance of the symposium organizer Professor Edward Yeung of Iowa State University, and Janet Cunningham of Barr Enterprises, HPLC 2014 assembled 770 delegates from 39 different countries of the world. This number included vendor representatives from 44 exhibitors for the three-plus day instrument, software, and consumables exhibition. The number of conferees was just over half of the attendance at HPLC 2013 in Amsterdam, The Netherlands, and in line with the HPLC 2012 symposium held in Anaheim, California. For some reason, the number of delegates for the United States version of this meeting has fallen off in recent times, perhaps analogous to the falloff in other analytical symposia such as Pittcon. However, other meetings such as the American Society for Mass Spectrometry (ASMS) Conference on Mass Spectrometry and Allied Topics seems to be gathering steam, undoubtedly driven by the recent surge in the use of mass spectrometry (MS) detection in chromatography and other analytical techniques.

The venue for HPLC 2014 was the New Orleans Hilton located right on the Mississippi River close to the convention center where Pittcon has been held many times. The five-day plus event had a total of 155 oral presentation in plenary talks and mostly in three parallel sessions, which made it a bit difficult to cover topics of interest that often ran at the same time. Fortunately, all three lecture halls were within a few feet of each other so getting from one session to another didn't pose much of a problem. At HPLC a total of 425 posters were presented in sessions with 25 different themes. Posters were up for the entire symposium so they could be viewed at almost any time of the day. With an ample social event schedule including three receptions and a symposium dinner and party, 10 vendor workshops, eight tutorial educational sessions, and five short courses (held during the previous weekend), attendees had their hands full deciding how to allocate their time. The tutorials were particularly well attended, some with standing room only, and covered current topics such as troubleshooting method development, polymeric monoliths, microfluidics, column myths, ultrahigh-pressure liquid chromatography (UHPLC) theory and practice, the effect of dwell volume, ion chromatography versus electrophoresis, and new Food and Drug Administration (FDA) regulations affecting high performance liquid chromatography (HPLC).

In this installment, I present some scientific highlights of HPLC 2014. This report also covers the various awards and honorary sessions that took place. Since it was virtually impossible for one person to adequately cover all oral and poster papers, my coverage will somewhat reflect a personal bias.

Trends in Liquid-Phase Technology and Techniques

Obviously, HPLC was the predominant technology in the technical sessions at the symposium, but sample preparation, the use of electrophoretic techniques (mostly in a capillary format), and an increase in supercritical fluid chromatography (SFC) papers were strongly evident. From a perusal of the poster and oral presentation abstracts, I broke down some of the major areas of coverage in this year's symposium and listed them in tables. These tables are useful to spot trends in the technology and new application areas for liquid-phase separations that were introduced in this series.

Table I: HPLC 2014 papers presented by technology or technique
Table I provides a rough breakdown of the coverage of liquid-phase technology and techniques in the separation sciences. Compared to HPLC 2013, some slight shifts in technology emphasis were noted. Again this year, new developments in column technology led the pack with oral presentations and poster papers dealing with many new phases and formats. However, compared to previous symposia in the series, the percentage of column-related talks actually dropped from a third of all presentations to a quarter of all presentations. Surprisingly, nearly 40% of the columns papers dealt with monoliths, with polymeric monolith coverage nearly 2:1 over silica-based monolith talks and posters. In the future, silica monolith coverage may grow because the patents are winding down and perhaps new companies may investigate the technology. Although not yet considered a commercial success, research interest, especially in academia, in monolith technology is still running high. The polymeric monolith segment is less covered by intellectual property rights than the silica monolith segment. Silica gel–based monoliths are seeing their second generation, and maybe a third generation, of commercial products with better efficiency, but slightly higher pressure drops because of the change in the macropore–mesopore domain ratios. Still, the silica monoliths are only available from one source. However, a continuation of new developments in polymeric monoliths devoted to the separation of small molecules has shown improvements in column efficiency. Originally, silica-based monoliths were considered to be best for small molecules and polymeric monoliths were thought to be optimum for large biomolecules only. Those beliefs are beginning to change as silica monoliths are being developed for large molecules and polymeric monoliths for small-molecule separations.

Three other "hot" areas in column technology this year were

  • Continuing with the observation made in my recent Pittcon article (1), superficially porous packings (SPPs, also referred to as shell particles, poroshell, core–shell, and fused-core packings) that rival the sub-2-µm particles in terms of column efficiency, but with substantially lower pressure drops are now the hottest area in HPLC and UHPLC. The poster and oral papers referring to SPPs outnumbered those devoted to sub-2-µm totally porous particles. The availability of sub-2-µm SPPs and up to 5-µm SPPs have expanded the use of these special particles to mainstream HPLC as well as UHPLC applications. At HPLC 2014, there were reports of even smaller SPPs than those currently commercially available.
  • Papers on two-dimensional (2D) and multidimensional chromatography doubled compared to last year's meeting. The technique is becoming more mainstream since major LC instrument companies now have easy-to-use accessories that provide accurate and rapid column switching and LC×LC (comprehensive LC) capabilities. For LC×LC, acceptance has also been brought about by the availability of more orthogonal stationary phases and column configurations such as short, fast SPP and monolithic columns for the second dimension. The 2D techniques are mainly useful when complex samples are encountered; food analysis was the most popular area for applications this year.
  • Microfluidics, microchips, and nanochannels were all part of a continuing theme both in oral and poster sessions. Undoubtedly, the strong interests of the symposium chair in this discipline probably accounted for a slight bias in acceptance of papers looking at smaller dimension columns and instrument design to accommodate them. One could also lump in micro- and nano-LC columns into this category that I didn't segment separately. All of these approaches not only result in solvent and sample savings, lower dispersion, and higher sensitivity, but also easier interfacing into detectors such as MS detectors. One paper even showed the use of the flame ionization detector, which can cope with a low solvent flow rate.

Table II: HPLC modes represented at HPLC 2014
In the columns area, I broke down the modes being used by HPLC 2014 attendees (see Table II). As always, on a relative basis, reversed-phase LC again dominated the usage (43% of all papers) with hydrophilic-interaction chromatography (HILIC) maintaining its position at a distant number two. HILIC serves as a separation technique for polar analytes that are weakly retained by reversed-phase chromatography. The number of chiral separation papers showed a strong number three with SFC applications a driving force.

Sample preparation technologies were well represented in the poster papers, but only five oral presentations were presented that had a sample preparation theme. No organized sessions were devoted to sample preparation this year. For poster presentations, the most prominent sample preparation subjects were solid-phase-extraction (SPE), on-column digestion of proteins using immobilized enzymes, protein precipitation for analyzing drugs and metabolites in biological fluids, and filtration. On-line SPE, related to the column switching approach discussed above, was the subject of several posters. New instrumentation accessories have made on-line SPE easier to perform.

Electrodriven separation techniques (such as capillary electrophoresis [CE], capillary zone electrophoresis [CZE], micellar electrokinetic chromatography [MEKC], and isoelectric focusing [IEF]) grew this year with a strong showing in both oral and poster papers with many applications papers depicting great strides in interfacing to MS. A continued lack of interest in capillary electrochromatography (CEC) was noted with only four presentations at HPLC 2014.