How Gas Chromatographs Work & How We Save You Time & Money

Excedr - Gas Chromatography Systems

Regardless of GC system configuration, Excedr’s equipment lease program is able to source all instrument types and can accommodate any model preferences you might have. Request an estimate today and see how leasing can benefit you.

All equipment brands/models are available

The Advantages of Excedr’s Gas Chromatography Instrument Leasing Program:

  • Eliminates the upfront cost of purchasing equipment by spreading its cost over time
  • Minimizes equipment downtime with included complete repair coverage and preventive maintenance
  • Takes advantage of potentially 100% tax deductible* payments, providing you significant cash-savings
  • Expedites the administrative work needed for instrument procurement and logistics
  • Conserves working capital,  enabling you to reinvest in your core business and operations (staffing, inventory, marketing/sales, etc.)
  • Accommodates all manufacturer and model preferences

*Please consult your tax advisor to determine the full tax implications of leasing equipment.

chromatography system diagram

Gas chromatography (GC) is a technique used for the separation and analysis of volatile and semi-volatile compounds (compounds that are easily vaporized at room temperature).

Separation occurs based on the interaction of molecules with the mobile phase and the stationary phase of GC. The less volatile molecules interact more with the stationary phase and move slowly, whereas more volatile molecules interact more with the mobile phase and move faster. When the analyte is detected the computer gives a peak with respect to the retention time of the sample. The area under the peak gives information about the concentration of the sample. This graphical data, specifically, the series of peak, is referred to as a chromatogram.

There are a number of components used in gas chromatography, which, together, make up instrumentation that is referred to as gas chromatography systems, GC systems, or gas chromatographs. These system allows scientists and researchers in the life sciences and pharmaceuticals industries, as well as industrial manufacturing, to isolate and analyze volatile compounds.

When using a GC system, a technician can obtain a compound analysis without causing decomposition of an analyte. For example, a gas chromatograph is typically used to separate different compounds in mixtures and test the purity of those substances. One of the few downsides to GC, however, is that it can only analyze compounds up to a certain molecular weight.

In general, the GC process involves two phases: mobile phase and stationary phase. The mobile phase regards a carrier gas, which is often a nonreactive or inert gas. Helium is the standard choice for most devices. The stationary phase refers to a microscopic layer of polymer or liquid that is set on an inert support inside tubing which is generally made of glass or metal. 

Gas analysis occurs after the gasses react with the walls of the stationary-phase coated column, which causes each individual compound to elute at different times. In GC, elution refers to the extracting of a material from another. This elution is referred to as the retention time of the compound, and comparing these times provides helpful data that makes GC analysis so useful.

Methods, Benefits, & Aerograph Machine Cost

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While there are many modes of GC, such as vapor-phase chromatography (VPC) and gas-liquid partition chromatography (GLPC), they all refer to the same separation of gases. Many methods exist to customize the analytical uses of gas chromatography, and are as follows:

Carrier Gas

Standard carrier gases include helium, hydrogen, argon, and air, but the gas that is chosen is generally determined by the specific detector being used. Other times, it is chosen to match the sample as the chosen gas will not show up on the readout, which can be helpful on occasion.

The mobile phase carrier gas is typically held within a cylinder and is passed through a molecular sieve as it enters the GC column and interacts with the stationary phase. This sieve removes unwanted impurities, such as hydrocarbons, water vapor, and oxygen, which can all cause base line noise and reduce sensitivity, possibly increasing detection limits.

Furthermore, the flow rate of the carrier gas is an important consideration. That’s because, while a high gas flow rate can potentially reduce retention times, it can also lead to poor separation. Making sure to perform GC using an ideal flow rate will result in higher resolution and better measurement.


Inlet Type

The inlet, or injector, is dependent upon whether the analyte is in a liquid, gaseous, solid, or adsorbed form and whether the sample has to be vaporized. Already dissolved samples can be added directly onto the column, while gaseous samples are often injected using a gas valve system. Adsorbed samples that need to be vaporized have their own injection methods.

Some of the common sample injection methods used are categorized as either hot and cold injection. Hot injection methods include split/splitless (S/SL) and total volume injection, while cold injection methods include cold on-column injection (OCI) and programmed temperature vaporization (PTV).


Column Selection

GC column choice is similarly dependent on the sample, with the polarity of the mixture being paramount. The polarity of the column stationary phase needs to match closely with the sample to increase resolution and decrease run time.

The two most common columns used in gas chromatography include packed columns and capillary columns. Packed columns are short, thick columns made of glass or stainless steel tubes and have been used since gas chromatography was introduced. Despite having low separation performance, packed columns can handle large sample volumes and are typically not susceptible to contamination. Using packed columns, the vapors (carrier gas) come into the stationary phase, achieve equilibrium with the moving gas phase and come back again in a series of steps, adsorbing and desorbing. Each step is called a theoretical plate.

Capillary columns are more commonly used these days due to their ability to perform excellent separation. These columns are well-suited for analysis that requires high-sensitivity. They consist of a thin, fused silica glass tube that has an internal liquid phase coating.


Column Temperature

The column in a GC is located inside an electronically controlled oven, so when speaking about the column temperature it refers to the heat of the oven which governs the column’s temp. The most important factor in determining temperature is finding the right compromise between how long the analysis will go and how much separation needs to occur.

This is important in the same way gas flow rate is important. If you use a high temperature, the sample will move through the column faster, (in conjunction with flow rate of the mobile phase). However, the faster it moves, the less it interacts with the stationary compound, and the less it interacts with the stationary compound, the less the sample separates. This can lead to suboptimal analyses.


Stationary Compound

Polarity is once again paramount when choosing the stationary compound, as it should have similar polarity to the solute. Common choices include, but are not limited to, cyanopropylphenyl dimethyl polysiloxane, bis cyanopropyl cyanopropylphenyl polysiloxane, carbowax polyethylene glycol, and diphenyl dimethyl polysiloxane.


GC Instruments

These instruments are extremely useful but can seem somewhat confusing mechanically when inspecting them from the outside. Understanding the components of the chromatograph can help make troubleshooting issues simpler. There are three main components:

  • GC Detectors: There are many possible detectors that can be used in a GC, but the two most common are the thermal conductivity detector (TCD) and the flame ionization detector (FID). These are commonly chosen as the TCD is universally applicable and FIDs are very sensitive toward hydrocarbons. In addition to TCD and FID, electron capture detectors (ECD) and nitrogen phosphorous detectors (NPD) are also used. ECDs are specifically used when halogenated compounds must be analyzed, and NPDs are used when nitrogen- or phosphorous-containing compounds must be analyzed.
  • Inlets: The choice of inlet allows the user to introduce a continuous flow of carrier gas to the sample. There are many different injector options, with many being more effective depending on the type of carrier gas that is going to be used.
  • Autosamplers: This component provides the inverse of what the inlet offers, offering a means of introducing the sample automatically into the inlets. There are several different types of autosamplers that can be interchanged based on the needs of your lab.

Furthermore, gas chromatography systems are often integrated with other chromatography techniques and systems. They are commonly paired alongside mass spectrometers as well. This is due to the fact that the combination of these powerful analytical methods results in increased functionality and throughput.

For example, GC/MS systems allow for the separation of complex mixtures, the quantification of analytes, and the identification of unknown peaks, as well as the determination of trace levels of contamination in various samples at increased rates.


We Offer Gas Separator System Leases to Fit Every Need

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If you’re interested in separating and analyzing organic compounds using gas chromatography systems, or wish to combine the analytical powers of mass spectrometry with gas chromatography, we can help. 

Lease your next GC/MS system with Excedr and save on upfront costs, protect your instrumentation with repair and preventive maintenance, and manage cash flow more easily through affordable and predictable scheduled payments. 

Furthermore, if you’re interested in standalone or tandem mass spectrometers, we can help you with that too. Call us at (510) 982-6552 or complete our contact form and we can discuss your customizable leasing options in detail.

Operating Lease

This off-balance sheet financing structure provides three options at the end of the term. The lessee has the option to return the equipment to the lessor, renew at a discounted rate, or purchase the instrument for the fair market value. Monthly payments are also 100% tax deductible which yields additional monetary savings.


If you recently bought equipment, Excedr can offer you cash for your device and convert your purchase into a long-term rental. This is called a sale-leaseback. If you’ve paid for equipment within the last ninety days, we can help you recoup your investment and allow you to make low monthly payments. This also frees up money in your budget rather than tying it down to a fixed asset.

GC System Manufacturers & Models on the Market
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Intuvo 9000 GC System, 7890B GC System, 490 Micro GC System, 490-PRO Micro GC System, 490-Mobile Micro GC System, 490 Micro GC Biogas Analyzer

Thermo Fisher:
TRACE 1300 Gas Chromatograph, TRACE 1300 Mainframe, TRACE 1300 Mainframe MS, TRACE 1310 Gas Chromatograph, TRACE 1310 Mainframe, TRACE 1310 Mainframe MS, TRACE 1310 DFS/IRMS Mainframe

Nexis GC-2030 Gas Chromatograph,GC 2014 Gas Chromatograph, GC-8A Gas Chromatograph, System GC, Multi-Dimensional Gas Chromatograph, Comprehensive GC-MS (GCxGC-MS) System

PPB Level Analysis Series 5900, Team Programmable Series 826, Isothermal Series 580, Academic Series 400, Argon Gas Series AR710/720, Dual Detector Series 8100, Process Series 200

GCxGC-EDC/FID, L-PAL3, Pegasus BT, Pegasus GC-HRT+, GCxGC-HRT+, Pegasus BT4D, Pegasus BT 4D-GCxGC, Pegasus GC-HRT+ 4D, Pegasus 4D-C

OI Analytical:
BTEX Analysis System, FBA 5320VPH Analysis System, VOC Analysis Systems, S-PRO 3200 GC System, 5390 Tandem PID/XSD, 4450 Tandem PID/FID, 5350 Tandem PID/ELCD, 4430 Photoionization Detector, 5360 XSD, 5383 Pulsed Flame Photometric Detector

Clarus 590 GC, CLARUS 690 GC,Clarus SQ 8 GC/MS, Clarus SQ 8S GC/MS, Clarus SQ 8T GC/MS, Torion T-9 Portable GC/MS, Arson Analysis by Automated Thermal Desorption-GC/MS,Phthalates Determination by GC/MS, Bioethanol Alcohol Determination by GC, Biodiesel FAME Determination by GC, Model Arnel 4035 Light Hydrocarbons by FID, Model Arnel 4032 Fixed Gases for TCD, Model Arnel 4050 Detailed Hydrocarbon Analyzer, Model Arnel 1115 Refinery Gas Analyzer,Model Arnel 4025 Trace Sulfur by SCD Analyzer, Model Arnel 1117 High-Speed Refinery Gas Analyzer, QSight 210 MD Screening System,Biodiesel Methanol Determination by Headspace-GC, Biodiesel Glycerin Analysis System 230V

Modular Alliance Series for GC, 8610c GC Mainframe, 310GC Chassis, SRI Preconfigured GC Systems, SRI-8610-5400-1, SRI-8610-5675-1, SRI-8610-5405-1, SRI-8610-3070-1, SRI-8610-1117-1, SRI-8610-0270-1, SRI-8610-0114-1, SRI-8610-0080-1, SRI-8610-0072-1, SRI-8610-0065-1, SRI-8610-0040-1, SRI-8610-0035-1, SRI-0310-1000-1, SRI-0310-0004-1, SRI-8610-0059-1, SRI-8610-0050-1, SRI-8610-0065-1, SRI-8610-5400-2, SRI-8610-5675-2, SRI-8610-5405-2, SRI-8610-3070-2, SRI-8610-1117-2, SRI-8610-0114-2, SRI-8610-0080-2, SRI-8610-0072-2, SRI-8610-0071-2, SRI-8610-0065-2, SRI-8610-0059-2, SRI-8610-0040-2, SRI-8610-0035-2, SRI-0310-1000-2, SRI-0310-0004-2, SRI-8610-0050-2, SRI-8610-0270-2, SRI-8610-0059-2

Xevo TQ-GC Mass Spectrometry System, Water Atmospheric Pressure Gas Chromatography

and more!


Operating Capital Benefits

Operating Capital Benefits

Excedr's operating lease structure allows you to keep your business credit line open for expansions, staffing, and other operational expenses. Additionally, it strengthens the cash flow of your business and keeps cash reserves free for business development opportunities.

Effects on Credit

Effects on Credit

Leasing / renting provides you with non-dilutive financing and does not hinder your future borrowing ability. You're able to acquire the equipment you need without the baggage associated with traditional financing.

Speed of Approval

Speed of Approval

Excedr's program allows you to respond quickly as your need for equipment and technology arises. You can be approved with minimal documentation and have the equipment you need in operation and generating revenue for your business quickly.

Refurbished Equipment

Refurbished Equipment

Unlike traditional financing and leasing companies, the Excedr program can accommodate refurbished equipment in addition to demo units. If you are looking for additional cost-savings, we recommend considering this option.