HP 5890 Series II with 7673 Autosampler
....the GOLD standard

HP 6890 Coupled with HP 5973 MSD

What is Gas Chromatography?

Chromatography is the separation of a mixture of compounds (solutes) into separate components so that they can be identified and quantified. By separating the sample into individual components, it is easier to identify (qualitative)) and measure
the amount (quantitative) of the various sample components. There are numerous chromatographic techniques and corresponding instruments. Gas chromatography (GC) is one of these techniques. In gas chromatography (GC), a moving gas (the mobile phase) carries the sample across a stationary phase (the solid support found within a GC column).  It is estimated that 10-20% of the known compounds can be analyzed by GC. To be suitable for GC analysis, a compound must have sufficient volatility and thermal stability. GC is normally used when the sample can be vaporized below 400-450°C.

GC History;

It was nearly 50 years from Mikhail Tswett's description of chromatography. The suggestion to use a gas as the mobile phase was made by Martin and Synge in 1941, but it was not implemented until the work of James and Martin (1952) on gas-liquid chromatography and the work of Cremer and Prior (1951) and Cremer and Müller (1951) on gas-solid chromatography. Since then, gas chromatography has developed rapidly, particularly during the 1960s and the use of the technique has been applied in almost every area of analytical and biochemical researches. The introduction of chemically bonded fused silica capillary columns was a very recent innovation in gas chromatography, more commonly referred to high resolution gas chromatography (HRGC).

Every gas chromatograph includes the following key components: flow controller, a sample introduction device, column, oven, detectors, and data handling system. A powerful and widely used combination is to couple a GC to a mass spectrometer (MS) to form a GC/MS system. A mass spectrometer measures the molecular weight of a compound to provide data for both quantitation and qualitative identification. It usually provides greater sensitivity and far more specificity than most other LC detectors.  At GMI, you will find knowledgeable staff to guide you through proper instrumentation choice with respect to your application and budget.

How to do GC?

In gas chromatography (GC), the sample is vaporized and injected onto chromatographic columns and then separated into many components. The elution is brought about by the flow of an inert gaseous mobile phase. In decent decade the development of gas chromatographic skill and its applications have been phenomenal. It has been estimated that as many as 200,000 gas chromatographs are currently in use throughout the world.

The carrier gas serves as the mobile phase that elutes the components of a mixture from a column containing an immobilized stationary phase. In contrast to most other types of chromatography, the mobile phase dose not interact with molecules of the analytes.

Carrier gases, the mobile phase of GC include helium, argon and nitrogen which are chemically inert. The stationary phase in gas-solid chromatography is a solid that has a large surface area at which adsorption of the analyte species (solutes) take place. In gas-liquid chromatography, a stationary phase is liquid that is immobilized on the surface of a solid support by adsorption or by chemical bonding. Gas chromatographic separation occurs because of differences in the positions of adsorption equilibria between the gaseous components of the sample and the stationary phases.

In GC the distribution ratio is dependent on the component vapor pressure, the thermodynamic properties of the bulk component band and affinity for the stationary phase. The equilibrium is temperature dependent. Hence the importance of selecting the stationary phase of column and column temperature programming in optimizing a separation.

Why HP / Agilent?  While there is choice in the marketplace it is GMI's opinion that the simplest, highest value, most rugged / durable choice with least risk and downtime...ie., lowest cost of ownership is an HP (Hewlett Packard) / Agilent system.

Historically speaking:

HP defined the market.

1965

HP enters the analytical instrumentation field with the acquisition of GC manufacturer F&M Scientific Corporation of Avondale, Pennsylvania. The acquisition allows HP to further expand its measuring and testing expertise into the area of chemical analysis.

1973

HP introduces first microprocessor controlled GC, the 5830.

1976

HP introduces world’s first benchtop GC/MS system, the 5992.

1979

HP introduces fused silica capillary columns for gas chromatography.

1984

HP introduces the 5890,
the best-selling GC in history.

1984

HP introduces electronic pneumatics control. EPC

1994

HP introduces first version of ChemStation software. Simplicity AND horsepower

1995

GMI is incorporated to provide laboratories  alternative service options for instrumentation and a venue to purchase pre-owned laboratory instrumentation certified to meet original manufacturer specifications

1996

HP introduces the 5973 MSD.

1997

HP introduces the Micro-ECD for the 6890. The detector incorporates the first major design changes in any ECD in the last 20 years.

AGILENT leads the pack (still)...

Jun 2005

Agilent introduces the 5975 inert MSD

January 2007

"GMI CERTIFIED" defines value in the "previously experienced" laboratory instrumentation market.

GMI formally introduces "GMI CERTIFIED^TM"  an industry leading methodology for reconditioning previously owned laboratory instrumentation AND providing a comprehensive documentation of work performed to ensure instrument fully meets original specifications and ships 'defect free'.

January 2005  GMI introduces inert ion sources for HP / Agilent mass specs.  Superior in sensitivity AND simpler to maintain !  With proprietary modifications GMI can provide superior technology solutions at a fraction of the price. Call today and find out how.
email: tfagrelius@gmi-inc.com

At GMI...its instrumental !

HP 5890 Series II GC, HP 6890 GC

GMI is able to provide GC and GC-MSD systems to meet your research and analytical requirements.  We stock Hewlett Packard GC main units and can supply detectors (FID, NPD, ECD, ELCD, PID, TCD, FPD and MSD), injection ports, autosamplers, and data handling solutions depending upon your analytical requirements and budget.

Based on your specific application requirements each GMI GC technology solution is customized for you, but lets start with an example starter system:

Example System A.
Hewlett Packard - 5890 GC-FID System Including: 5890 Series II GC, Flame Ionization Detectors, Split-Splitless Injection Ports with Manual Pneumatics, HPIB Communication, 7673B Autosampler Including: Controller, Injector, 100 Position Tray and Mounting Bracket.  Great for volatiles such as ethanol or biodiesel work.

Count on GMI to provide custom solutions based on your specific application, whether toxicology, environmental, or routine research.  GMI specialists can assist in tayloring solutions from drugs of abuse, to pesticide determination, to biodiesel turn-key systems!

	toxicology
	drug screening
	chemical analysis
	food safety
	law enforcement
	hydrocarbon processing
	biodiesel
	environmental
	pesticide analysis
	research laboratories

Please call a GMI technical sales consultant for
a quotation on a system at 763-712-8717

Agilent 6890 gas chromatograph

More on GC detectors:

The suite of gas chromatographic detectors includes (roughly in order from most common to the least): the flame ionization detector (FID), thermal conductivity detector (TCD or hot wire detector), electron capture detector (ECD), photoionization detector (PID), flame photometric detector (FPD), thermionic detector, and a few fringe / unusual or VERY expensive choices like the atomic emission detector (AED) and the ozone- or fluorine-induced chemiluminescence detectors. All of these except the AED produce an electrical signal that varies with the amount of analyte exiting the chromatographic column. The AED does that AND yields the emission spectrum of selected elements in the analytes as well. Another GC detector that is very powerful is the mass spectrometer. When coupled to a GC the detection system itself is often referred to as the mass selective detector or more simply the mass detector.

Placed at the end of a chromatographic column in a manner similar to the other GC detectors, the mass detector is more complicated than, for instance, the FID because of the mass spectrometer's complex requirements for the process of creation, separation, and detection of gas phase ions. A capillary column most often used in the chromatograph because the entire MS process must be carried out at very low pressures (~10^-5 torr) and in order to meet this requirement a vacuum is maintained via constant pumping using a vacuum pump. It is difficult for packed GC columns to be interfaced to an MS detector because they have carrier gas flow rates that cannot be as successfully pumped away by normal vacuum pumps; however, capillary columns' carrier flow is 25 or 30 times less and therefore easier to "pump down." That said, GC/MS interfaces have been developed for packed column systems that allow for analyte molecules to be dynamically extracted from the carrier gas stream at the end of a packed column and thereby selectively sucked into the MS for analysis. For one type interface, using a silicone membrane, the selectivity for organic molecules (the analyte) over helium (the carrier gas) is 50,000.

The high cost for the pump, ionization source, mass filter or separator, ion detector, and computer instrumentation and software has limited the wide application of this system as compared to the less expensive GC detectors (e.g., FID cost ~$3000; entry level MSDs cost over $15,000). However, the power of this technique lies in the production of mass spectra from each of the analytes detected instead of merely an electronic signal that varies with the amount of analyte. These data can be used to determine the identity as well as the quantity of unknown chromatographic components with an assuredness simple unavailable by other techniques.

When you buy a pre-owned (GMI Certified) GC system from GMI, it arrives to your lab fully tested and ready to use...guaranteed !  NEW to GC analysis.   No problem, come to GMI for a comprehensive training and familiarization course taught by true experts. GMI has Agilent trained staff to assist in eliminating your start-up learning curve.

  GMI, Inc.
  6511 Bunker Lake Blvd.  
  Ramsey,   Minnesota, 55303   USA
  Tel. 763-712-8717          Fax 763-712-8724 
  Send electronic mail to richard@gmi-inc.com