What is Gas Chromatography, and How Does Gas Chromatography Work?

Gas Chromatograph Rosemount Analytical Emerson 700XA

Gas chromatography is a method to separate and analyze vaporized compounds in a carrier gas using a gas chromatograph. The process of gas chromatography begins with the injection of a sample into the instrument. Then, the sample is vaporized and carried through the capillary columns by carrier gas. As the compound elutes from the capillary columns, it passes through a detector where it is quantified. Finally, the data from the detector is collected and analyzed to determine the identity and concentration of each compound in the sample.

What are the advantages of gas chromatography?

Emerson Rosemount Analytical Figure 1 - The Functional Components of A Gas Chromatograph

Gas chromatography is a highly advantageous analytical technique used for the qualitative and quantitative analysis of chemical compounds. One of the main advantages of gas chromatography is its high sensitivity and specificity, allowing it to detect trace amounts of compounds in mixtures. This makes it an ideal tool for analyzing complex samples with multiple components. Gas chromatography also offers high levels of accuracy and reproducibility, making it an ideal choice for gas measurement applications.

Why is gas chromatography important?

Emerson Rosemount Analytical 700XA Gas Chromatograph

Gas chromatography allows accurate analysis of the chemical composition of samples in the pipeline. It detects possible impurities at specific measurement points throughout the gas process from upstream to downstream. This detailed analysis provides insight into the energy quality of the pipeline gas, enabling companies to ensure that it meets all tariff requirements and helping to identify potential problems in their process. Furthermore, by establishing detailed benchmarks based on numerous previous analyses, they can monitor changes in the qualities of their gas over time and identify any abnormalities that may indicate an issue. Most importantly, gas chromatographs act as a “cash register” in custody transfer, allowing companies to determine the value of the gas for billing purposes. In short, gas chromatography is essential for natural gas companies to ensure not only the safety of their products but also their ongoing success.

Gas chromatographs also play a part when customers use ultrasonic meters for measurement.  The gas energy flow rate is determined by multiplying the measured volumetric flow rate by the measured calorific value (AGA 5). Volumetric flow is measured in accordance with AGA 3, 7, or 9 as required by choice of primary flow elements. When used with AGA 3 and AGA 7 flow rates, the gas chromatograph reports the energy and refines the volumetric flow measurement. With AGA 9, the chromatograph takes on a new role. In addition to providing measured calorific values, it serves as a partner in ensuring quality flow measurement by providing compositional data necessary to calculate the speed of sound.

How to choose the right gas chromatograph for your needs

Firstly, when selecting gas chromatography equipment, there are many factors to consider. The decision should involve thoughtful consideration of the purpose and associated requirements, such as sample size and type, budget and available space, and overall performance capability. Choosing the right machine for the job is essential for delivering accurate results in an efficient and timely manner.

The Rosemount Gas Chromatograph – The Standard in Natural Gas Custody Transfer Applications

Rosemount’s gas chromatography products are a trusted name for dependable online analysis of natural gas applications, offering cost savings and decades of expertise. Boasting over forty years of experience and 12,000+ GC installations worldwide, the Rosemount XA series provides highly accurate results with reliable repeatability – setting the bar in industry standards!

The exceptionally resilient Rosemount XA gas chromatography series is designed and tested to guarantee optimum reliability, even in the most extreme climates (ranging from -20°C to 60 °C/-4 °F to 140 °F). This series includes the 370XA, 470XA, 700XA, 770XA, 570, and 500 gas chromatographs. To ensure the protection and optimal performance of your equipment, our Cherokee Integrations and Solutions team offers various turnkey gas chromatography enclosure and integration packages,

Field services, training, and ongoing operational maintenance and support programs are available through Cherokee Technical Solutions. Our experienced and safety-certified technicians are happy to help you commission, calibrate and provide on-demand maintenance to ensure your GC is operating at peak performance.

Gas Chromatograph Frequently Asked Questions

What is a process gas chromatograph?

A process gas chromatograph (also known as a GC) is an analytical instrument used to separate and analyze mixtures of gaseous and vaporized compounds in a carrier gas. It works by injecting the sample into the instrument, vaporized by heat, and pushed through capillary columns with a carrier gas. As the sample elutes from the capillary columns, it passes through a detector where it is quantified. Data from the detector is collected and analyzed to determine the identity and concentration of each compound in the sample.

What are some applications of gas chromatography?

Gas chromatography can analyze many samples, including natural gas, liquefied petroleum gases (LPGs), biogas, organic vapors, and other industrial gases. It can also be used to detect impurities in these samples or to measure their composition. Common applications include custody transfer measurements, quality control and assurance tests, pipeline leak detection, process optimization, product purification, and environmental monitoring.

What are the 2 types of gas chromatography?

Two main types of gas chromatography can be used to analyze gaseous and vaporized compound mixtures: capillary column gas chromatography (GC) and packed column gas chromatography. Capillary column gas chromatography (GC) is a type of GC in which the columns used for separation are much narrower (typically 0.25 – 0.53 mm in diameter) than those used for packed column GC (1-4 mm). This type of chromatography is more sensitive and has a shorter analysis time, but it is also more expensive. Packed column gas chromatography involves the use of wider columns that are packed with solid particles like beads or pellets. This type of chromatography is more economical and has a longer analysis time, but it is less sensitive than capillary column GC.

What is a carrier gas?

A carrier gas is used in gas chromatography and other analytical techniques such as mass spectrometry. It is an odorless and non-reactive gas that helps to move the sample through the device and assists in separating the components within it. Commonly used carrier gases include helium, hydrogen, nitrogen, and argon. Some gas chromatographs use multiple types of carrier gas to achieve better separation of components.

What temperature range can a gas chromatograph operate in?

Most gas chromatographs are designed to work within a specific temperature range (generally -4 °F to 140 °F). The temperature must be maintained within this range for optimal performance. In addition, the temperature should not exceed the maximum limit of the instrument’s materials to prevent damage caused by excessive heat. Temperature controllers or chillers may be necessary to maintain a consistent temperature within the range.

Gas chromatography is a powerful tool for analyzing and monitoring natural gas quality. With the right equipment, such as Rosemount Analytical Gas Chromatographs, it can guarantee reliable results at an affordable cost. You can ensure your gas chromatograph operates optimally with minimal downtime or disruption through field services and training offered by Cherokee Technical Solutions coupled with custom integration packages from Cherokee Integrations & Solutions.

If you’re interested in learning more about how a GC could be used in your next measurement application, don’t hesitate to contact us today.