New Chromatography Columns and Accessories at the 2005 Pittcon Conference: Part I

Pittcon 2005 — the 56th Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy — returned to the Orange County Convention Center, Orlando, Florida, 27 February–4 March 2005. This year's event hosted more than 900 instrument manufacturers and 1aboratory suppliers in more than 2300 booths. In addition to attending the exposition, the conferees were able to listen to numerous oral presentations, view more than 900 posters, check out 38 seminar rooms, or attend one of 150 short courses.

Ronald E. Majors

Although many specialty meetings and symposia have sprung up as competition, Pittcon still remains the most important yearly international analytical exhibition, where companies introduce their latest instruments, instrument accessories, columns, sample preparation products, and other consumable products. Because many past attendees have purchased one or more new products within three months of attending the show, most exhibitors attempt to maximize their booth traffic to meet as many potential customers as possible.

The purpose of this report is to provide information about many of the new separation consumables and accessory products that will be displayed at Pittcon 2005. In some cases, products that were introduced during 2004 but after Pittcon 2004 (1,2) are included for reasons of completeness. The information is based upon manufacturers' responses to a questionnaire mailed in December 2004. Because of space limitations and the fact that some of the manufacturers did not respond to the questionnaire, this report cannot be considered an exhaustive listing of all new products that were introduced in Orlando. However, over the years, these Pittcon introduction summaries have provided a good source of information that would be difficult for one individual to gather during the four days of the exhibition. In addition, the products introduced have shown definite correlations to current research, development, and application activity in the separation sciences.

Companies Listed in This Column

As in previous years, columns and other products recommended by their manufacturers primarily for biomolecule separations or sample preparation are denoted in the tables with the designation BIO. Some of these products can be used for general high performance liquid chromatography (HPLC) separations as well, but their main emphasis is for biological samples. I will cite specific information about bioapplications where appropriate. Because HPLC columns for microbore (1.0–2.1 mm i.d.) and high-throughput HPLC (lengths less than 50 mm) are now numerous, they will be covered in the individual modes. This year, I have extended the columns and sample preparation accessories to include various kits that are designated to solve specific applications problems as well as small hardware items that supplement the chromatograph.

In this month's coverage, I will describe new introductions in the areas of high performance liquid, reversed-phase, normal and bonded-phase, ion-exchange and ion, size-exclusion, large- and preparative-scale-, and specialty chromatography columns. Next month, I will look at gas chromatography (GC) products, sample preparation products, and hardware, accessories, and kits for chromatography and sample preparation.

Table I: New series of HPLC columns at Pittcon 2005

Trends and Highlights

General:

This year, I observed a definite trend toward miniaturization of the chromatographic experiment, not only with the preparation of smaller samples in the microliter to submicroliter range but also in the dimensions of the columns, especially in the increasing use of short, sub-2-μm columns in HPLC and LC-mass spectrometry (MS). Still, a large number of products will be introduced for the separation, sample preparation, and LC-MS measurement of biomolecules, still the hottest area in chromatographic research and applications. New breeds of low bleed phases and ultra-inert surfaces for both GC and LC-MS were noted. Monolith technology continues to see new entries in both the polymeric- and silica-based arenas. Applications-specific solutions packages with everything needed to perform sample prep and analysis are in vogue.

HPLC columns: Reversed-phase HPLC maintains its dominance and a significant number of regular reversed-phase and specialty reversed-phase columns were introduced. Particles and column internal diameters are getting smaller, and columns are getting shorter with sub-2-μm particles now being offered by several companies. No irregularly shaped silica gel packed columns in analytical sizes were introduced this year; spherical packings now dominate. A new silica-based monolithic column line was introduced, and additional polymeric monolith columns appeared. Flash chromatography, new preparative and process columns, and the availability of bulk packing seem to have had a renaissance, undoubtedly driven by the need to purify new drug candidates and biomolecules. Specialty columns were numerous, with 60% of them recommended for protein/peptide separations. Finally, an HPLC lab-on-a-chip product has been commercialized. Other columns, such as those for chiral, sugar-oligosaccharide, and environmental samples, were among the most popular.

Table II: Reversed-phase chromatography columns at Pittcon 2005

Gas chromatography: GC columns were highlighted this year with more introductions of lower bleed phases and ultra-inert phases that provide enhanced sensitivity, lower baseline drift during temperature programming, and improved MS capability. As usual, many application-specific columns were introduced, especially for use in the separation of environmental compounds such as pesticides and polychlorinated biphenyls. One instrument manufacturer introduced an entirely new, full line of capillary columns.

Sample preparation: Products for the preparation of tiny amounts of samples in the microliter and submicroliter range were quite prevalent. Formats such as 48- and 96-well (solid-phase extraction) SPE plates, pipette tips for SPE and filtration, syringe filters, and trapping columns for proteomics were noted. Drugs in biological fluids, environmental contaminants, and proteins were the most popular application areas. A particularly novel prespotted target device for matrix-assisted laser desorption ionization (MALDI)-MS was introducted.

Table III: Preparative and process columns

Accessories: Twenty-two new accessories for LC, GC, capillary electrophoresis (CE), capillary electrochromatography (CEC), and sample preparation were noted. New general-purpose products such as vials, caps, fittings, and ferrules seemed to be very popular this year. In GC, new designs of inlet liners and seals, nonstick septa, a GC-MS interface, accessories for simulated distillation, and space-saving gas generators were noted, while for LC, a packaged postcolumn reactor, column oven, prepackaged, sterile solutions and buffers, and nanospray adaptors for MS stood out.

New Series of HPLC Columns and Packings

Each year, manufacturers introduce entire new families of HPLC columns at Pittcon. For the sake of brevity, I have elected to cover those series here instead of listing each column under individual headings in the modes' tables. Table I covers those new families of HPLC columns and packings displayed at Pittcon 2005. In some cases, the series are major extensions of existing products in the companies' offerings but cover an entire mode or group of phases, while in other cases, the series are entirely new to the market.

Figure 1: Fast protein separation. Column: 10 mm X 4.6 mm, 1.5-μm Prosphere HP ZAP! C18; mobile phase A: water with 0.1% trifluoroacetic acid; mobile phase B: acetonitrile with 0.1% trifluoroacetic acid; gradient: 25–75% B over 4 min; flow rate: 1.0 mL/min; detection: UV absorbance at 280 nm. Peaks: 1 = cytochrome C, 2 = lysozyme, 3 = β-lactoglobin, 4 = ovalbumin. (Courtesy of Alltech/Grace Vydac.)

This year, several products for flash chromatography and bulk-packing materials for those who wish to pack their own preparative and analytical columns were introduced. In recent years, flash chromatography has been made more convenient by the introduction of prepacked columns and dedicated instruments. Formerly, chemists would pack their own glass columns with large-particle silica gel or soft organic gels and by using gravity-fed systems, collect fractions from synthesized crude organic or protein mixtures. Now, there are almost as many flash chromatography phases available as there are HPLC stationary phases. For those preparing large axial-compression preparative columns, bulk materials can be purchased and packed or repacked as needed. A most interesting product in this area was the perfluorobenzene flash column from Jordi FLP (Bellingham, Massachusetts). Fluorophases are useful in reversed-phase chromatography because they display unique selectivity compared to the popular alkyl phases such as C8 and C18.

A new family of silica monolith columns called Onyx was introduced by Phenomenex (Torrence, California). Until this year, Merck KGaA (Darmstadt, Germany) was the only major supplier of these products, but they have sublicensed this technology to Phenomenex. Silica monolith columns provide about half of the pressure drop but equivalent efficiency to 3–5 μm microparticulate columns. Silica monolithic columns are more useful for small-molecule separations than polymeric monoliths, which seem to be focused on the rapid separation of biomolecules.

Figure 2: Elements of the HPLC chip for protein identification. (Courtesy of Agilent Technologies.)

Reversed-Phase Chromatography

As usual, many new reversed-phase columns were introduced at Pittcon 2005 (see Table II). If one also adds in the reversed-phase columns covered in the new series (Table I), preparative (Table III), and specialty (Table IV) tables, one can see clearly the dominance of this operational mode. Silica-based bonded-phase columns dominated the introductions but polymeric, polymer-coated, and hybrid phases are growing.

During the last several years, the average particle size of analytical columns has been decreasing. A decade ago, 5-μm columns were the most popular, but columns packed with 3.0–3.5 μm packings have become more widespread in use. For the first time, a large number of sub-2-μm reversed-phase columns were introduced at Pittcon 2005 (Table II). In this range, particle diameters ranged from 1.5 to 1.9 μm. Smaller particles packed into short columns, usually with lengths of 50 mm and less, provide increased plate counts so that separations formerly performed on longer columns packed with larger particles (for example, 5-μm) can be accomplished in a fraction of the time. For example, the average number of theoretical plates generated on a 150 mm × 4.6 mm column packed with 5-μm column particles might be in the range of 12,000-14,000. This number of plates also can be generated by a 100 mm × 4.6 mm packed with 3.5-μm particles or by a 50 mm × 4.6 mm column packed with 1.8-μm particles. The advantage of decreasing the column length is faster separations, because at constant flow rate, separation time is proportional to column length. Indeed, these short, fast HPLC columns are finding increased use in high-throughput and LC-MS environments. As the particle size decreases, pressure goes up with the inversed particle diameter squared, but the shorter columns reduce the overall operating pressure. High-efficiency, high-speed separations of less than a minute or two are typical for such columns. To properly use such high-efficiency columns, some care must be exercised, because instrumental considerations such as extracolumn effects, gradient delay volumes, and detector response times become increasingly important. To illustrate the use of a fast HPLC column, Figure 1 gives an example of a high-speed (2.5-min) protein separation using the ProSphere HP ZAP! C18 column (Alltech/Grace Vydac, Deerfield, Illinois). This column was only 10-mm long and was packed with 1.5-μm particles with a bonded C18 phase with 500-Å pores. A fast water-acetonitrile-TFA gradient was used to accomplish this separation, run at a flow rate of only 1.0 mL/min. On a 3-μm C18 column, approximately 12 min was required to accomplish this same separation.

Table IV: HPLC specialty columns

In terms of phase chemistry, as usual, the C18 phase was the leading chemistry (approximately 50% of total) with C8 (13%) being a distant second, followed by fluoro and phases with alkyl chain lengths greater than C18 (8% each), then phenyl, polar-embedded alkyl, and C4 (5% each). The others were 3% or less.

Due to the large number of reversed-phase chromatography materials, this year, I classified the phases according to their suggested chemistry or application emphasis of the manufacturer based upon their provided information. For example, a "Regular" category means that the manufacturer did not specify any unusual characteristics or applications. In another popular category, the polar-embedded phases are recommended for use in low-organic, highly aqueous environments, even up to 100% water. This type of phase incorporates (embeds) a polar functional group such as an amide into the alkyl bonded-phase chain itself. The phase is primarily hydrophobic but with hydrophilic groups near the surface or in the alkyl chain that can be "wetted" with polar eluents. The fluoro phases are interesting in that they display a quite different selectivity compared to the more common C18 phases. For example, fluorinated alkyl phases have shown increased selectivity for the geometrical isomers of substituted phenols.

Table IV: HPLC specialty columns, continued

During the last several years, long-chain alkyl phases up to C30 have been introduced. This year saw three reversed phases: C22, C27, and C30. These long-chain phases provide a greater degree of shape selectivity than a typical C18. An example in which these phases bring added value is in the separation of cis-trans carotenoid isomers. They also appear to be more resistant to phase collapse at low percentage of organic solvent in the mobile phase.

Among the more interesting phases introduced at Pittcon 2005 was a high-temperature phase (as high as 200 °C), a C8 silica monolith, and two new inorganic-organic hybrid phases, one from Waters (Milford, Massachusetts) and one from Phenomenex (Torrance, California). The first HPLC-chip column and LC-MS interface system based upon microfluidics technology was introduced. Figure 2 shows this HPLC chip (Agilent Technologies, Palo Alto, California) that contains a trapping (enrichment) column, an analytical column (dimensions 40 mm × 0.050 mm packed with 5-μm Zorbax SB C18), a six-port valve interface, an electrospray MS spraying needle, high-voltage contacts, and a microchip identification tag. This HPLC chip is inserted into the LC–MS interface module, which automatically advances the electrospray tip for optimum placement into the MS source. On the inlet end, the gradient nanopump connects through the six-port valve to the HPLC chip.

Table IV: HPLC specialty columns, continued

Normal Bonded-Phase and Adsorption Chromatography Columns

Normal-phase chromatography still has its place in the separations laboratory, especially for water-sensitive samples, for analytes that are insoluble in water, for certain geometric isomers difficult to separate by reversed-phase chromatography, and for class separations. Organic solvents used in normal-phase separations are more MS-friendly than some of the typical buffers used in HPLC. In reversed-phase chromatography, HPLC operating conditions must be modified dramatically sometimes, to allow compatibility with MS detection. Hydrophilic interaction chromatography (HILIC) is a separation mode for very polar compounds that might not retain on a reversed-phase column adequately. The technique is analogous to normal-phase chromatography, in which a hydrophilic stationary phase such as bare silica gel is used. The mobile phase is mostly organic and solutues elute in order of increasing hydrophilicity. HILIC is also an MS- and evaporative light-scattering detection (ELSD)-friendly technique; sometimes volatile salts are used for highly charged molecules to prevent ion suppression in MS.

In the new series section (Table I) and in the preparative-process section (Table III), suppliers of silica-gel columns also would fall into this category. Chromolith Si (Merck KgaA, Darmstadt, Germany), a high-purity monolith silica column, was introduced at Pittcon 2005. Monolithic silica displays lower pressure drops than microparticulate columns, yet offers similar column efficiency. With low pressure drop, columns can be coupled together to generate high plate counts for difficult separations. Bare titania columns were offered by ZirChrom Separations (Anoka, Minnesota). Their Sachtopore Titania columns are available in particle sizes ranging from 3 μm up 80 μm and pore sizes from 60 to 2000 Å. The columns can be used under extreme conditions in the pH 1–14 range and at temperatures as high as 150 °C. Bulk packing is available.

Figure 3: The separation of proteins by size exclusion on the NanoFilm SBC-150 column. Column: 250 mm x 4.6 mm, 5-μm NanoFilm SEC-150; mobile phase: 0.1 M phosphate buffer, pH 7.0; flow rate: 0.25 mL/min; detection: UV absorbance at 214 nm; temperature: ambient (23 °C); injection volume: 5 μL. Peaks: 1 = thyroglobulin (670 kDa), 2 = BSA dimer (132 kDa), 3 = BSA (66 kDa), 4 = lysozyme (14.3 kDa), 5 = A peptide (1.5 kDa), 6 = uracil (120 Da). (Courtesy of Sepax.)

Cyano- and amino-derivatized packings can be used with reversed-phase solvents as short, lower retention reversed phases or with organic solvents in the normal-phase mode. Bischoff Chromatography (Leonberg, Germany) introduced its ProntoPEARLsub-2 TPP NH₂ column. The aminopropyl functional group bonded to 1.8-μm silica (phase coverage: 4%) permits this column to be used in both the reversed- and normal-phase modes. Because columns are very short (lengths of 14–50 mm), they are recommended for high-throughput separations.

Two new column sets were mentioned specifically as being suitable for HILIC: the Develosil Silica-HILIC (I) and the Develosil Silica-HILIC (II) from Nomura Chemical Company (Seto, Japan); and the Alltima HP HILIC from Alltech, now a division of Grace Vydac. Both families of HILIC columns are recommended for highly polar compounds such as urea, uracil, and cytosine and certain drug metabolites. The Develosil columns are packed with 3- or 5-μm spherical silica particles. The Silica-HILIC (I) is pure silica, which shows good peak shape for chelating compounds, while the Silica-HILIC (II) is a metal-doped silica that is reported to be five times more stable than conventional silica. The Alltech HP HILIC column is available in 1.5-, 3-, and 5-μm sizes of high purity silica particles (120-Å pores). Columns are constructed of stainless steel and have internal diameters of 2.1, 4.6, and 7.0 mm. Guard columns are available.

Figure 4: The separation of cationic, nonionic, and anionic surfactants in a single run on the Acclaim Surfactant column. Column: 150 mm x 4.6 mm, 5-μm dp; mobile phase A: acetonitrile, mobile phase B: 0.1 M ammonium acetate, pH 5.4; gradient: 25-85% A in 30 min, then hold 85% A for 10 min; temperature: 30 °C; flow rate: 1 mL/min; sample solvent: 25:75 (v/v) acetonitrile-0.1 M ammonium acetate, pH 5.4; injection volume: 25 μL; detection: evaporative light scattering. Peaks: 1 5 xylene sulfonate, 2 = lauryldimethylbenzyl ammonium chloride, 3 = octylphenoxyethoxyethyl dimethylbenzyl ammonium chloride, 4 5 Triton X-100, 5 = decyl sulfate, 6 = dodecyl sulfate, 7 = C10-LAS, 8 = C11-LAS, 9 = C12-LAS, 10 = C13-LAS. (Courtesy of Dionex.)

Ion-Exchange and Ion-Chromatography Columns

This year, fewer ion-exchange columns were introduced compared with previous years. Some of them were noted in the new series section (Table I) and in the specialty column section (Table IV). In this section, introductions from Dionex (Sunnyvale, California) and Showa Denko (Kawasaki, Japan) are highlighted. The Shodex IC SI-91 4C and IC YS-506D ion chromatography columns both were based upon a polyvinyl alcohol packing material. The former column is packed with a 9-μm spherical anion exchanger bead with quaternary ammonium functionality and has dimensions of 100 mm × 4.0 mm. It is recommended for the separation of oxyhalides such as chlorate, bromate, and iodate, which can be separated and detected at the 10-ppm level with a UV detector. The 5-μm YS-506D packing contains carboxyl functionality and is therefore recommended for cation analysis. This column, with dimensions of 150 mm × 6.0 mm, provides a good separation for the ammonium and sodium ions while ensuring good peak shape for the doubly charged calcium and magnesium ions.

The Dionex columns were based upon a 7.5 μm co-polymeric resin bead that consists of a polyvinylbenzene ammonium polymer crosslinked with divinylbenzene. The stationary phase consists of a novel hyperbranched anion exchange polymer electrostatically attached to the surface-sulfonated wide pore (2000 Å) polymeric substrate. This is new polymer bonding technology that allows excellent control of column selectivity and capacity through alternating treatments of epoxy monomer and amine. Two columns were introducted: the IonPac Fast Anion III column (dimensions: 250 mm × 3.0 mm; guard column: 50 mm × 3.0 mm) and the IonPac AS21 column (dimensions: 250 mm × 2.0 mm; guard column: 50 mm × 2.0 mm). The IonPac Fast Anion III column allows fast analyses of polyvalent anions in both simple and complex samples. A suggested application would be the analysis of phosphate and citrate in soft drinks, including diet sodas. The IonPac AS21 column was designed to be compatible with LC-MS eluents such as methylamine, as well as compatible with ion chromatography eluents such as potassium hydroxide. Recommended for the analysis of perchlorate in drinking water, ground water, and other matrices according to EPA Method 331.0, the column also can be used for the separation of arsenate, chromate, iodide, and tungstate.

Large-Scale and Preparative-Scale Chromatography

Whether the user is an organic chemist who wants to purify a potential blockbuster drug candidate, an analytical chemist who is asked to prepare some enantiomerically pure isomer, or a biochemist who desires to get an ultrapure monoclonal antibody for further experimental work, preparative chromatography often is required to perform the task. The need for larger amounts of purified material necessitates the use of larger diameter columns. Sometimes, for simple mixtures, the use of flash chromatography is sufficient to accomplish the purification task. At other times, small particle size (5-μm) preparative columns of 21.2 mm i.d. might be required to separate a pair of closely resolved compounds of interest. For cost and pressure-flow requirements, 10-μm preparative particles often represent a good compromise. To develop a preparative separation, generally, it is advisable to begin with an analytical scale column. This is because, during method development, one wants to use smaller amounts of sample, less solvent, and wants to develop the method relatively quickly. Thus, a 2.1- or 4.6-mm i.d. column can be chosen for method development. As long as the packing material and column geometry is constant, a linear scale-up to a preparative column can be performed.

Table III lists the preparative columns and packings that were shown at this year's event. Many of the introductions were bare silica gel, long considered the staple in normal-phase preparative chromatography. Several of the silica gel packings are available in bulk for those employing their own column packers. Bare titania, another normal-phase packing, also was introduced as a preparative material. Particles with bonded coatings also were introduced. Similar to analytical HPLC, reversed-phase chromatography on C18 is also a popular option for preparative users. Because sample throughput is an important performance factor in preparative chromatography, a high carbon loading is important because it allows larger samples to be injected. Bonded-phase columns introduced at Pittcon 2005 had higher-than-normal carbon loads. A quaternary amine polymeric packing in disposable flash chromatography columns, silica monolith prep columns, and a bonded-phase titania-based wide-pore reversed-phase column were among the more unique offerings.

Sometimes, preparative amounts represent only microgram quantities. The MagPrep from Merck KGaA is used for the isolation of genomic DNA, and 1 mL of total particles is enough for 100 extractions.

Size-Exclusion Chromatography

Each year, a few new size-exclusion chromatography (SEC) materials can be found on the Pittcon exhibit floor. This year, three new products emerged from Sepax Technologies (Newark, Delaware), Jordi FLP, and Showa Denko. The lone silica-based product was the Nanofilm SEC column from Sepax. Using uniform, nanometer-thick hydrophilic polymer brushes to deactivate the underlying silica, the columns are recommended for the size separation of proteins using very low salt concentrations. With nominal pore sizes of 150, 300, and 500 Å, a wide variety of proteins can be handled, up to more than a million daltons in size (see Figure 3). Recoveries of greater than 90% were observed for bovine serum albumin (BSA) and lysozyme, the latter being a highly positively charged protein that is difficult to elute from many packing materials, especially at low salt concentration (for example, 50 mM). Particle sizes of 3, 5, 7, 10, and 15 μm give the user a wide latitude in analytical and preparative applications. Column dimensions range from 2.1 mm i.d. to 21.2 mm i.d. and lengths up to 30 cm. Guard columns are available to protect the analytical and preparative columns.

The Shodex OHpak SB-807HQ is a 30-μm spherical polyhydroxymethacrylate polymer bead that is underivatized. It is recommended for aqueous SEC. With an average pore size of approximately 1000 Å, it is recommended for very high molecular weight distribution measurements. One cited application was the size separation of the ultrahigh molecular weight bialuronic acid that has an average molecular weight of 3 million.

The Jordi offering, Jordi Fl.A.S.H, is based upon a fluorinated divinylbenzene spherical polymeric resin with particle sizes ranging from 1 to 80 μm. With perfluorobenzene functionality, the packing shows less adsorption than conventional polystyrene-divinylbenzene (PS-DVB) resins. Available pore sizes range from 100 to 10⁵ Å, giving a wide range in SEC separations for analytes with molecular weights ranging from 100 to 10⁶. When used in an aqueous solution, the packed columns also can be used for reversed-phase chromatography.

Specialty HPLC Columns

Specialty columns are HPLC columns that have been developed for specific separations that are difficult to achieve on a standard column. However, manufacturers sometimes will use a standard column but test it specifically for a certain class of compounds and provide a recommended set of chromatographic conditions. In some cases, the specialty column comes as part of a "total solution" kit with reagents, standards, and method. Most specialty columns will be delivered with a test chromatogram from an analysis performed at the factory before shipment, and some are guaranteed. Table IV shows the 25 specialty columns that were presented at Pittcon 2005. Silica gel-based columns and polymer-based specialty columns were divided about equally.

The largest single category of specialty columns was that designated for the separation of biomolecules, mainly proteins and peptides. Approximately 60% of the specialty columns of Table IV were in this category. Capillary and nano columns that were designed specifically for LC-MS were introduced by several companies. Capillary and nano columns, with internal diameters as low as 0.075 mm, have major advantages for the small samples encountered in proteomics because they can provide good sensitivity in sample-limited cases and can be interfaced directly into the MS source. Fractionating a peptide digest on a cation exchange capillary with subsequent desalting (via an reversed-phase trap column) and transferring fractions to a reversed-phase nanocolumn then to an MS-MS system is catching on as an alternative technique to two-dimensional gel electrophoresis.

A variety of selective columns for protein analysis and purification using principles such as affinity and immobilized metal affinity chromatography (IMAC) were introduced at Pittcon 2005. Some representative examples include columns introduced by BIA Separations (Ljubljana, Slovenia), a leader in polymeric monolith columns, who displayed a nonporous methacrylate column with immobilized IDA metal chelate phase. Shodex (Showa Denko, Kawasaki, Japan) showed an affinity chromatography column based upon Protein G, while Grace Vydac (Hesperia, California) had a Protein A ligand, the latter recommended for the isolation of monoclonal antibodies. Orachrom's (Woburn, Massachusetts) offering was a copolymeric packing that was selective for glutathione binding sequences.

Hydrophobic interaction chromatography (HIC) is a useful technique for the separation of proteins in which it is important for the protein to remain intact. In HIC, no organic modifier is used in the mobile phase to prevent potential denaturization of sensitive proteins. Only aqueous buffers are used in the mobile phase. Reverse salt gradients are used in which the buffer concentration is decreased as a function of time. Such columns were introduced by Tosoh Bioscience (Montgomeryville, Pennsylvania) and Nacalai Tesque (Kyoto, Japan).

In the non-life science area, Dionex introduced a column for surfactant analysis that is capable of separating both ionic and nonionic surfactants in a single injection. Figure 4 shows an example of the three types of surfactants that can be separated in a single injection. In the past, more than one column was required to separate all three surfactant types. Restek's (Bellefonte, Pennsylvania) UltraQuat column was designed for the separation of highly charged environmentally important amines such as paraquat and diquat and employs a chaotropic separation mechanism using a prepackaged buffer. Zirchrom Select (Zirchrom, Anoka, Minnesota) is a mixed-mode carbon-clad zirconia packing that contains both reversed-phase and cation-exchange functionality. This combination provides unique selectivity for the separation of certain isomers.

Acknowledgment

I would like to thank the manufacturers and distributors who kindly furnished the requested information in advance of Pittcon 2005, thus allowing a timely report on new product introductions. For those manufacturers who would like to be considered for inclusion into the Pittcon 2006 coverage, please send the name of the primary company contact, the mailing address, fax number, and e-mail address to

LCGC North America

, 485 Rte. 1 South, Bldg. F, Iselin, NJ 08830, Attn.: Pittcon 2006 "Column Watch."

References

(1) R.E. Majors,

LCGC

22

(3), 230–242 (2004).

(2) R.E. Majors, LCGC 22(4), 322–337 (2004).

Ronald E. Majors "Column Watch" editor, Ronald E. Majors, is business development manager, Consumables and Accessories Business Unit, Agilent Technologies, Wilmington, Delaware, and is a member of LCGC's editorial advisory board. Direct correspondence about this column to "Column Watch," LCGC, Woodbridge Corporate Plaza, 485 Route 1 South, Building F, First Floor, Iselin, NJ 08830, e-mail lcgcedit@lcgcmag.com.