Focus on Separation Science at Pittcon® 2012: Advances in Gas Chromatography

For gas chromatography (GC), the big news at Pittcon® 2012 was the absence of Agilent (www.agilent.com) and PerkinElmer (www.perkinelmer.com). This was a consequence of an overall downsizing caused by the “six-year effect” where the cycles of ACHEMA and Analytica coincide. Many firms are reluctant to increase promotional spending, so compromises must be made. The reduction of spending at Pittcon was evident across the board, but was particularly strong in GC. Twenty years ago, Pittcon was viewed by spectroscopists as the world’s largest meeting in separation science. Slowly at first, the focus shifted: At Pittcon 2012, spectroscopy clearly dominated the exhibition.

New gas chromatographs

SCION™ GC/MS systems

Bruker (www.bdal.com) has a long history of innovation in mass spectrometry, so when the company acquired the Varian GC and quadrupole mass spectrometers, I expected interesting advances. It didn’t take long. The new SCION™ SQ™ (single quadrupole) and TQ™ (triple quadrupole) GC/MS systems—which won the Pittcon Editors’ Silver Award—utilize unique ion optics to improve signal-to-noise. For example, the TQ uses an elliptical ion path to cancel out noise. Plus, active focusing of the helium molecules reduces dispersion, which improves peak heights.

The mass spectrometers are designed to enable the nonspecialist to use the power of MS detection without the hassle of complicated method setup and data analysis. For example, the SCION TQ GC/MS/ MS facilitates multiple reaction monitoring (MRM). The operator enters the name of the analyte, and the MRMs autofill from a library of 2500 analytes. Supporting application notes for food, beverage, environmental, forensics, sports medicine, and petrochemicals are available. When coupled to either the Bruker 436 or 451 GC, the entire package has a very small footprint. The 451 GC has flame ionization detection (FID), electrochemical detection (ECD), thermal conductivity detection (TCD), thermionic specific detecton (TSD), and pulsed flame photometric detection (PFPD) options. Other options include purge and trap, programmable temperature vaporizer (PTV), and solid probe inlets.

Bruker also upgraded the software to the CompassCDS™ 3.0 Scalable Software Solution. As the name implies, the software scales from a single instrument and PC to multiple chromatographs in a client server mode. Specific applications such as natural gas, transformer oil PIONA, and simulated distillation are supported via application-specific plug-in modules. The CompassCDS is 21 CFR Part 11-compliant, with audit trails and encrypted all-in-one data files

GCMS-QP2010 SE GC/MS

Entry-level quadrupole mass spectrometers continue to decline in price, reflecting improved design and higher unit volume, which justifies more tooling. To seize this advantage, Shimadzu Scientific Instruments (www.ssi.shimadzu.com) introduced the GCMS-QP2010 SE. The design focuses on economy and simple operation of basic features. Ion optics are optimized with a high-performance quadrupole mass filter. Fully automated MS tuning provides consistent results. The instrument can use most common columns, provided the carrier gas flow is no greater than 4 mL/min. The SE also includes an ecology mode that reduces function and electrical power by about 50% when the run sequence has been completed.

Company founders Genzo Shimadzu, Sr. (1839–1894) and Genzo Shimadzu, Jr. (1869–1951) were honored as recipients of the 2012 Pittcon Heritage Award for their contributions to metrology. The senior Shimadzu founded the firm in 1875 to provide service to imported instruments and also manufacture distillation devices and Atwood machines (accelerometers). The younger Shimadzu expanded the firm into balances and spectrographs, including X-ray.

TRACE 1300 Series GC

In many labs, each GC is dedicated to a single application, often operating 24/7. They are optimized at purchase for the application. Also, a small footprint improves productivity since one can squeeze more chromatographs onto the bench. With these macros in mind, Thermo Fisher Scientific (www.thermofisher.com) introduced the TRACE 1300 Series GC. The instrument can be configured with a range of injectors and detectors as dictated by the application. The company seems to favor the ion traps or quadrupole. The volume of some detectors has been reduced to improve detection sensitivity. Injector backflushing is available. The human interface is via a computer for the 1300. The TRACE 1310 uses an icon-based touchscreen.

TRIDION™-9 GC/TMS

Over the last five+ years, Torion (www.torion.com) introduced a series of portable GC/MS instruments. Each generation shows significant improvements over prior models. The TRIDION™-9 is the latest and most portable. It still uses a toroidal ion trap mass analyzer (TMS), but the weight has been reduced to 30 lb, including the helium cartridge for the carrier gas. Typical run times are less than 3 min. Target applications include chemical-biological warfare (CBW) agents, environmental, and food safety.

CANARY-3™ and LIGA-GC

Defiant Technologies (www.defiant-tech.com) introduced two novel GC systems with micromachined columns and detector for environmental monitoring. The CANARY-3™ starts with a choice of three thermal desorption preconcentrator inlets tuned to different volatility ranges. For high volatiles, a torturous path preconcentrator has a very high surface-to-volume, finned structure that supports sorptive coatings. The coatings are sol-gels, which provide high capacity, selective retention, and low mass. Upon heating, the low thermal mass releases the analytes in a plug to the GC. The column is a work of micromachined art. It is a three-layer sandwich called the LIGA-GC. The center is a nickel coupon with an array of holes. The “bread” is a LIGA machined serpentine that connects the holes in series to give a 1-m column the size of a dime. For 10 m of length, the column is layered to form a cube, smaller than a sugar cube.

Detection is with a delay-line surface acoustic wave microbalance resonator, which is about the size of a dime. The resonator is coated with a thin sorptive polymer. The sorption/desorption process produces a signature that is unique to each analyte. Two cells are used: One is for reference, and the other monitors the column effluent. A microprocessor converts the difference to a signal that is proportional to the detected mass. Detection limits are low picogram levels.

At the other end of the booth was the FROG-4000™, a handheld micro GC system for monitoring volatile organics, including BTEX (benzene, toluene, etc.), alcohols, ketones, etc., with an analysis time of less than 5 min with a temperature-programmed run. The interior design is similar in design to the CANARY, but is equipped with a photoionization detector (PID) and extended front legs to sit on a pond perimeter or stream bank. I asked what chemicals were responsible for the natural stream bed smell, and was told that it was “geosmin” (4S, 4aS,8aR)-4,8a-dimethyl-1,2,3,4,5,6,7,8-octahydronaphthalen-4a-ol. The human nose has a detection threshold of about 5 ppt.

800 Series thermal energy analyzer

In the mid-1970s, Thermo Instruments was a startup manufacturing a nitrosamine detector for GC and LC that was as sensitive as it was expensive and large. This was a niche market mostly dealing with cigarette smoke. Thermo moved on to other things, and ultimately sold off the detector product line. Over time, Ellutia acquired the technology (www.ellutia.com). This year, the company introduced the 800 Series TEA (thermal energy analyzer), which includes an embedded GC and detector. The 800 operates in two modes, each of which is specific for nitrogen analytes. In the nitrogen mode, GC effluent passes through a catalytic pyrolyzer operating at 700 to 850 °C, which oxidizes the analytes to NO and on to nitrosamines. Ozone gas is added, which forms excited NO2*. This rapidly decays to the ground state by emitting light, which is detected with the photomultiplier.

For assaying nitro and nitroso analytes, the column effluent is pyrolyzed under reducing conditions. The resulting NO is reacted with ozone to produce NO2*, which decays rapidly by emitting light at 600 nm. Detection sensitivity compared to carbon is 107. The detection limit is <2 pg/sec.

CALIDUS™ micro GC

Last year at Pittcon, Falcon Analytical (www.falconfast.net) introduced the CALIDUS™ Model 101-HT micro gas chromatograph, which provided very fast separations in a portable instrument. This year the news was 1) Falcon was purchased by SGS Group Management (www.sgs.com) and 2) the CALIDUS provides a complete simulated distillation of petroleum, meeting the requirements of ASTM Method D2887 in 9 min or less. Chrom Perfect® process control software from Justice Laboratory Software (www.justiceinnovations.com) now controls and takes data from the CALIDUS.

GC sample preparation

Success in assays by GC often requires selecting appropriate sample preparation. Thus, several firms introduced new technology to fill application niches.

LC-GC 9000

According to Brechbühler (www.brechbuehler.ch), coupling LC to GC offers simple sample prep with high enrichment, high resolution, and improved detection sensitivity. The sample is fractionated by LC. Fractions of interest are transferred by a hard plumbed valve to a high-volume GC injector for GC separation, including any conventional GC detector such as MS or MSn. Switching the LC column effluent to GC can be based on time or triggered by detector response. Noneluting materials for the LC stage are backflushed to waste. The entire instrument is called the LC-GC 9000. Since Brechbühler is a channel partner for Thermo Fisher Scientific, the preferred modules are the TRACE Ultra GC with large-volume on-column injection and Phoenix 40 binary pump for the LC. One application was the residual oil in recycled cardboard, which is used for food packaging.

GPC sample preparation

Power-Prep™ GPC

Of course, LC in the form of gel permeation chromatography (GPC) has been used for decades for off-line sample prep for GC. Gilson (www.gilson.com) continues to promote a GPC feeding a fraction collector, which then serves as an autosampler for GC. Fluid Management Systems (www.fmsenvironmental.com) introduced the Power-Prep™ GPC system. Each disposable column is packed with cross-linked polystyrene/divinylbenzene bead-packed PTFE tubes. Pesticide residues, polychlorinated biphenyls (PCBs), and dioxins appear to be the major focus of the Power-Prep. Sorbents for solid-phase extraction (SPE) are silica gel, alumina, Florisil™ (U.S. Silica Company, www.ussilica.com), and C18. Cleanup with GPC reduces solvent, expensive glassware, and operator time compared to manual methods.

Static headspace sampling

Master static headspace sampler

Headspace sampling of air above a liquid sample has evolved over the last 35 years. It is still attractive, since headspace analysis is not labor-intensive, provides excellent detection limits, and avoids risks of contamination with other samples and the operator. The Master static headspace sampler from DANI (www.danispa.it) provides a carousel sample tray for 120 vials. Each vial is identified by bar code. Vial size ranges from 10 to 22 mL. Before analysis, the oven controls the sample temperature of 18 vials, with constant, user-controlled incubation time. A shaker accelerates and improves efficiency, improving detection sensitivity and reducing variability. The automatic leak check ensures sample integrity.

Sampling uses a valve and loop flow path for reliability and precision. The sample path is entirely chemically inert and thermostated. This guarantees complete transfer of the sample and eliminates carryover. Applications include blood alcohol, residual solvents in pharmaceuticals and food packaging, BTEX in water, and residual monomers in polymers. The Master also supports purge-and-trap sampling, which improves the detection limit by 100 times compared to prior models. The Master is compatible with all known GCs. Optional tray cooling is designed for biosamples.

Versa headspace vial sampler

Static headspace sampling is popular because it is fast, easy, and works well for volatile organics (VOCs) in a range of matrices. Teledyne Tekmar (www.teledynetekmar.com) relies on years of experience to offer a range of headspace samplers. The latest, the Versa, features a small footprint, yet holds 20 × 22 mL vials. The sample pathway is constructed of inert materials and can be heated to 200 °C. The headspace sampler performs an automated leak checking protocol for trouble detection and resolution.

Sampling dissolved gases

Eclipse 4660 purge-and-trap sample concentrator/4551A water autosampler

Good business in the analytical instrument industry is often a case of being in the right place with the right product at the right time. Sampling dissolved gas, especially methane, is a case in point. Fracking of gas-producing strata has raised concerns about dissolved gases, particularly methane, in water supplies. O.I. Analytical (www.oico.com) presented a poster describing the use of the Eclipse 4660 purge-and-trap sample concentrator and 4551A water autosampler for fracking studies of methane in water. A significant number that will require remediation were found.

LGX50 sample preparation module for GC

Sampling liquids for dissolved gases is a real engineering challenge since gas–liquid interfaces must be avoided. Attempting to move a liquid too quickly produces cavitation, compromising the sample. With these constraints in mind, EST Analytical (www.estanalytical.com) introduced the LGX50 sample preparation module for GC via the U.S. EPA’s RSK175 (3810) protocol. The LGX50 contains two racks for 50 40-mL septum-sealed vials. One rack holds the samples; the other holds blank vials with a stir bar. Before adding sample, the vial is purged with He to remove CO2 and air. A controlled aliquot of the liquid sample is transferred to the evacuated blank vial along with an internal standard. The sample liquid is protected from external contamination or analyte loss. The sample is heated and stirred for a proscribed time before transferring the headspace to the sample loop for assay by GC with appropriate detectors such as an FID for hydrocarbons.

Model 7400 for sampling dissolved gases

CDS Analytical (www.cdsanalytical.com) introduced the Model 7400, also for sampling dissolved gases in water. The 7400 features a 72-position autosampler with three trays for 24 vials. Internal standard addition is automated. All sample contacting pathways are PEEK, silica, or electroformed nickel for reduced carryover and contamination.

Model 4000 pyrolyzer

Pyrolysis of solids combined with GC often provides unique signatures that facilitate tracing the origin of the material. For example, a poster from CDS compared pyrograms of various plastics to confirm that they were indeed made with renewable materials. Some were as advertised, but others appeared to be copolymers of both bio and petroleum sources. The Model 4000 pyrolyzer from CDS quickly in stalls on any GC. It uses a resistively heated platinum coil that can be heated at any rate between 0.01 °C/min and 20,000 °C/sec. GC in particular often uses canisters for sampling volatile analytes.

Gas sampling technology is often split between canisters and sorbent tubes. Canisters are suitable for total sampling, including permanent gases, while sorbent tubes are more suitable for analytes that are reactive with sorbents or condensable

CIA Advantage

Markes International, Inc. (www.markes.com) introduced the CIA Advantage™ for automated analysis of VOCs in canisters. The CIA is designed for 27 canisters, which enables unattended 24/7 operation. Addition of internal standard is automated. No cryogen is required, saving thousands of dollars per year. Carryover is reduced to less than 0.2 ng by heating the transfer lines to 200 °C. With GC/MS, the detection limits are less than 0.1 ppb. Using the selected ion monitoring (SIM) mode on the MS reduces the detection limit to less than 10 ppt.

Model 2012 air sampler

The Model 2012 air sampler from CDS Analytical is optimized for the collection of volatile organics according to U.S. EPA Method TO-17. The compact, portable air sampler has a capacity of four tubes. An embedded computer controls all functions, including sequential sampling for up to 12 hr with a booster battery.

Two-Stage Brass Small-Profile Regulator/Analytical Series Point-of-Use Manifolds

In chromatography, smaller is generally better. Airgas, Inc. (www.airgas.com) introduced two complementary products to supply high-purity gases for GC and other purposes. The new Two-Stage Brass Small-Profile Regulator is much smaller, which reduces the footprint, opening up new design possibilities for the lab. The clean sweep flow path quickly flushes residual gas, which can be a concern after changing cylinders

With good reason, many labs locate the gas supply outside the laboratory. Airgas presented Analytical Series Point-of-Use Manifolds, which are intended for high-purity gas use (99.9999 percent pure). These manifolds incorporate a packless diaphragm inlet valve, compact regulator (above), and outlet metering valve, providing gas control at the bench. Multiple manifolds can be mounted onto a single back plate so that all gases are in the same panel.

Injection syringes

Diamond Design

As detection limits in GC/MS get smaller, chromatographers are discovering design problems that had not been seen before. Take the common syringe—SGE (www.sge.com) found that the old design occasionally had problems with carryover traced to the adhesive that joins the needle hub to the glass barrel. Occasionally, the adhesive was not filled to the end, leaving an exposed annulus, or the adhesive could contact and thus contaminate the sample. To eliminate this, SGE introduced the Diamond Design, in which a PTFE seal isolates the barrel from the metal tip. This also increases syringe lifetime by 10 times.

Solid-phase extraction

SPE-Xpress™

U.S. EPA Method 1664 for oil and grease just got easier with the introduction of the SPE-XPress™ from Environmental Express (www.envexp.com). Each unit is capable of processing three 1-L water samples in parallel with a throughput of about 1/hr/station. The SPE-XPress filters a 1-L sample and extracts the oil and grease from the SPE disk with n-hexane. The hexane solution is collected in a tared aluminum pan, where it is evaporated to dryness and ready for weighing. User-friendly software controls internal steps, such as verification of complete sample processing and conditioning of the SPE disk, plus makes data available to a LIMS.

Stir bar for the Twister®

Stir Bar Sorptive Extraction (SBSE) with the GERSTEL Twister® (www.gerstel.com) is a simple, economical technique for extracting and concentrating analytes from solutions. Extraction efficiency depends on partitioning between the sorbent on the stir bar and the sample matrix. This year, the company introduced the EG-S ethylene glycol-silicone coated magnetic stir bar, which provides polar (H-bonding) selectivity to complement the PDMS sorbent. PDMS preferentially sorbs nonpolar analytes. Use of both bars provides an overall analyte profile of volatile and semivolatile organic compounds. After sorbing the analytes, the Twister bar is loaded in a thermal desorption injector to the GC. Since the EG-S bar also sorbs some water, the solvent vent mode is recommended. The EG-S phase has a Tmax of 220 °C.

Sample drying

PowerVap Concentrator

Dryng samples is probably the biggest time sink in most sample preps for chromatography. If one is not careful, samples can be overdried and thus destroyed. With these and other pain points in mind, Fluid Management Systems introduced the PowerVap Concentrator, a standalone direct-to-vial concentration system that processes up to six samples in parallel but with individual control of each. For example, the evaporation/drying of material in each of the the six wells is monitored continuously with optical sensors. When the endpoint is reached, the flow of drying nitrogen is turned off, along with the heater. The sample is collected in a 500-µL or 1-mL autosampler vial, which is attached to the bottom of the larger sample tube.

MultiPurpose Sampler

A similar sample-drying module was introduced by GERSTEL GmbH & Co. (www.gerstelus.com) for the MultiPurpose Sampler (MPS). Samples are concentrated under user-defined temperature and vacuum. Solvent exchange for improved detector compatibility is a common task that can be selected by a mouse click in a sequence table. The MPS is used in GC, HPLC, and MS. GERSTEL also introduced a shaker module for the MPS, which provides either shaking or vortexing up to 3000 rpm. Up to eight vials can be processed at a time. Mixing movement is restricted to horizontal motion, which prevents sample loss on the vial cap.

Hydrogen generators for GC

Gas chromatography columns generally run better when hydrogen is the carrier gas. Plus, FIDs require hydrogen with very low organic contamination. The choice is usually between hydrogen generators and high-pressure tanks. Hydrogen generators have certainly improved. F-DGS SAS (www.f-dgs.com) exhibited a line of hydrogen generators for GC, including generators for multiple instruments. Hydrogen purity is better than 6 nines; maximum delivery pressure is 240 psi. Residual water is removed with a desiccant cartridge. Control is via a 128 × 64 touchscreen. Water is from a 2.3-L internal reservoir or can be plumbed directly from an external source of 10-megohm water or higher. No acid or base is required.

Columns for gas chromatography

Rtx®-BAC columns

New columns for assay of blood alcohol from Restek (www.restek.com/BACPlus) provide rapid (<2 min) isothermal, baseline separation of ethanol, methanol, acetone, tert-butanol, acetaldehyde, isopropanol, and n-propanol. The two-column set (BAC-1 and BAC-2) give chromatograms with changes in elution order, for confirmation of peak identification. Each column is individually tested with a BAC test mix.

Secondary columns for C×GC

Secondary columns in GC×GC need to be fast (i.e., short) and with broad selectivity. Restek introduced the Rtx 200 series (www.restek.com/catalog/view/32442/15124) as secondary columns with a trifluoropropyl surface chemistry that provides orthogonal selectivity to phenyl, cyano, and Carbowax stationary phases. The Rtx 200 columns are thermally stable, low bleed, and compatible with difficult analytes such as phenols. Tmax is 340 °C.

RT®-Alumina Bond/MAPD columns

Because of high selectivity, alumina is often preferred for separating light petroleum factions containing C2–C5, including olefins. Restek RT®-Alumina BOND/MAPD PLOT columns (www.restek.com/catalog/view/11267) provide rapid separation of hydrocarbons up to a Tmax of 250 °C. Stable response factors make the MAPD column ideal for process applications where recalibration must be minimized. The columns are available in fused silica and metal (MXT®).

MXT®-Q-BOND columns

Metal columns are more robust and hence suitable for portable instruments. Restek metal MXT®-Q-BOND and MXT-S-BOND PLOT phases (www.restek.com/chromatogram/view/GC_PC1184) were developed for the assay of oxygenated solvents. Columns are available in tight 3.5- or 7.0-in. coils.

Triart Hybrid columns

YMC America, Inc. (www.ymcamerica.com) extended its family of Triart Hybrid columns. Since their introduction, the high pH stability of the columns has attracted attention, but also raised the obvious question of scaleability. Some chromatographers are reluctant to develop analytical methods that do not scale to prep and potentially process. Thus, YMC introduced bulk phases on particle cuts of 10, 15, 20, and 50 μm. Now you can pack your own prep scale columns. The company also showcased its full range of particle sizes of the Triart C8.

Nano stationary phase technology

One poster in particular caught my eye. Dr. Allen Britten of Cape Breton University in Nova Scotia presented a series of posters on nano stationary phases with better efficiency and resolution than I’d seen before. Following is a quote from his poster abstract (2090-3P): "This current investigation is related to the evaluation of nano stationary phase (NSP) GC capillary columns for environmental sample analysis. The stationary phase has the same composition as that of conventional stationary phases, but due to its nano size, the particles form a specific orientation with the capillary surface. Surface bonding and crosslinking of the NSP provides superior thermal stability compared to that of high molecular weight polysiloxane stationary phases. Better selectivity of the NSP is due to a specific orientation, resulting in a stronger interaction of analytes. The selectivity and stability of NSPs are the two most important properties differentiating them from conventional stationary phases."

I’m sure that we will see much more on nano stationary phase technology in the near future.

Column hardware

SilTite™ μ-union

For five decades, SGE has built a reputation for producing small parts that solve real problems in separation science. The latest example is a very small and hence low-thermal-mass fitting (<0.5 g) designed to couple GC columns in a temperature-programmed oven. Cool spots must be avoided. The SilTite™ µ-union uses SGE’s double cone ferrule to make the seal without wrenches for fused-silica capillaries. This should be particularly useful in GC×GC or creating mixed column sets, including guard columns.

SilTite ferrules for GC injectors and detectors are available in graphite, Vespel® (DuPont, www2.dupont.com), and SGE’s proprietary SilTite FingerTite. The latter provides a strong, maintenance-free, creep-free connection. It is particularly recommended for GC/MS.

Click here for Dr. Stevenson's reviews of new instruments and columns for liquid phase separation, and supercritical fluid chromatography.

Robert L. Stevenson, Ph.D., is a Consultant and Editor of Separation Science for American Laboratory/ Labcompare; e-mail: rlsteven@comcast.net.

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