Focus on Columns and Consumables at Pittcon® 2011

Columns, chemicals, and consumables (CCCs) account for more than 30% of the chromatography market. The quantities are large. Globally, 400,000 active HPLCs produce two 100-car tanker trains of waste mobile phase per year. This cost nearly a billion dollars to buy and a similar number to dispose of. With an average of five columns/year, the number of columns is about two million. This seems low, since a few chromatographs run 24 × 7 and use hundreds of columns. Columns are a topic close to the heart of many chemists, since one can utilize one’s chemical training to use and even improve them.

SFC columns

Since there was so much interest in supercritical fluid chromatography (SFC) instruments, let’s lead with columns for SFC. SFC is often practiced with HPLC columns. This is successful, particularly with chiral phases such as AD, OD, and OJ. However, validated methods may look better if they use columns mainly qualified as SFC columns by the manufacturer.

YMC America (Allentown, PA) is on top of the SFC explosion with the introduction of 11 columns. Each is tested under SFC conditions prior to shipment. Surface chemistries are 2-ethylpyridine, diol (60 Å), N,N-diethylaminopropyl, pyridine, amide, propylacetimide, silica, diol (120 Å), amino, cyano, PVA-sil, and polyamine II. The columns are packed with 5-μm silica particles in 4.6 × 250 mm hardware. YMC can also provide other column lengths, diameters, and particle sizes by special order.

Four new Viridis™ SFC columns were displayed in the Waters (Milford, MA) booth. Stationary phase chemistries include 2-ethylpyridine, 4-ethylpyridine, fluorophenyl, and unbound BEH (ethylene bridged hybrid particle). The particles are all 1.7 μm in diameter, but can be scaled up to 5 μm for preparative separations using the same surface chemistry.

GreenSep™ columns from ES Industries (West Berlin, NJ) are specifically optimized and rated for SFC. GreenSep Amino Phenyl is recommended for analytes containing OH, COOH, and amines by SFC without the use of additives. GreenSep DEAP is noted for the excellent peak shape of amine and amino analytes without the use of peak shape enhancers in the mobile phase. GreenSep Ethyl Pyridine is also very effective in separating amino analytes. GreenSep Nitro is the phase of choice for isomers of aromatic analytes. If the nitro column does not work, GreenSep PFP has orthogonal selectivity. Hence, if one is not suitable, another is. Finally, GreenSep Pyridyl Amide provides good loading capacity and unique selectivity. Peak shape additives are seldom required. In summary, ES offers six attractive phases for SFC.

Recognizing the empirical nature of chiral stationary phase selection, Regis Technologies (Morton Grove, IL) has set up a service for screening an analyte against its library of chiral stationary phases (CSPs) using SFC and HPLC. Thus far, 519 analytes have been screened, and a 95% hit rate has been obtained with HPLC. This is similar to the success rate claimed by high-performance capillary electrophoresis (HPCE). The company also offers a similar service for SFC. Regis is equipped with Waters SFC 80 and 350 preparative SFCs, plus two analytical SFC instruments. The prep instruments can deliver mg to kg quantities, depending on the project. Obviously, this service would be very attractive for exploration studies. SFC is easy, but it is also different. Speaking from experience, experience is useful.

HPLC columns

Agilent’s (Palo Alto, CA) acquisition of Varian merged companies with major product offerings in consumables. Thus, it is not surprising that the page count of the new catalog for chromatography is now 1344 pages, a 50% increase over last year. To be fair, the new catalog also includes a few pages of supplies for spectroscopy.

Update on core-shell particles and columns

Stating in the late 1960s, core-shell column packings (e.g., Zipax) have followed a byzantine path to today’s editions. These are optimized to enable legacy HPLCs to better compete with the ultrahigh-performance liquid chromatographs (UHPLCs), at least in speed, as measured in peaks per second or total run time. The story began with DuPont Instruments (Wilmington, DE) and has traveled through several hands to wind up in Agilent’s today. Now several vendors offer core-shell particles with a basic design of a solid core of about 1.7 μm and a porous 0.5-μm-thick outer shell. The total particle diameter is thus about 2.7 μm. Columns packed with these particles have been a commercial success primarily due to improved run time offered to users of conventional HPLC instruments. Typical products include Poroshell (Agilent), Halo (Advanced Materials Technology. [Newark, DE]), and Kinetex® (Phenomenex, Torrance, CA). The newest is the SunShell core-shell packing from ChromaNik Technologies (Osaka, Japan) introduced at Pittcon® 2011. The bead has a particle diameter of 2.6 μm, which is 0.1 μm smaller than some traditional ones.1

Agilent’s press package for Pittcon 2011 contained a chronological listing of the important historical milestones for Agilent in chromatography. Interestingly, the last entry, dated January 2011, was titled, “Agilent Secures Patent for Porous Shell LC Particle Manufacturing Technology.”

With good reason, some customers avoid use of sole-sourced products. The claims in the patent,1 which are the protected points, appear to be limited to particles that are agglomerated with urea-formaldehyde polymer. The polymer is removed by calcination. Thus, the fears of sole-source scenarios are probably unfounded. Further, the introduction to the patent describes other synthetic approaches, most of which use technology that is already in the public domain. Agilent has therefore provided a road map for others to follow.

New column brands

Thermo Fisher Scientific (Waltham, MA) introduced Syncronis silica-based HPLC columns. The particles are either 1.7 or 5.0 spheres with 100-Å pore. The 5-μm particles are targeted for conventional instruments, and the 1.7-μm are reserved for UHPLC. The surface chemistry range is C18, C8, AQ, and phenyl, with others listed under the specialty phases (Tables 1 and 2). All are end-capped. The C18 phase has a high carbon load at 16% C. The benzyalmine test shows low silanol activity, which is expected for end-capped phases. No data were provided about column lifetime. In summary, the Syncronis columns appear to be competitive with other premium brands. Thermo also introduced the EASY-Column™ for nano-LC. Columns are packed in metal-free, fused-silica capillaries.

Table 1    -    New columns for reversed-phase liquid chromatography (RPLC) (source: interviews and trade literature)
Table 2    -    New specialty phase columns for LC (source: interviews and trade literature)

Agilent added a new series of columns, ZORBAX Rapid Resolution High Definition (RRHD) columns. These are built on 1.8-μm silica particle and are rated to 18,000 psi. They are now available in eight phases, including four C18 phases.

RPLC columns

RPLC columns continue to dominate the LC column space. This year, new products appeared to be extensions in the available phases to improve the choice in selectivity (Table 1).

The Acclaim Carbamate (Dionex) is designed to provide baseline separation of all critical pairs in U.S. EPA Method 531.2 using linear solvent gradients. Bonding is stable, giving exceptionally low bleed, which is useful with MS detection. The Acclaim RSLC 2.2 columns are designed for labs that have huge sample loads. Depending on the separation, throughput can be increase 15× compared to conventional HPLC. Plus the solvent per sample is reduced by a similar factor. Dionex also points out that the shorter columns give sharper peaks, which can reduce the amount of sample required by 60–85%. The Pmax for 50-mm column length is 9000 psi; the 100-mm length is 12,000 psi. For conventional HPLCs, Dionex offers the same surface chemistry on 3-μm-diam silica, also with a 120-Å pore. The Pmax is 4500 psi.