What is GMCS Testing?

GMCS Testing, or gas chromatography-mass spectrometry testing, is one of the most advanced, precise and widely used techniques in analytical chemistry.

For testing batteries and accumulators, discover the battery test chamber, designed for testing under controlled conditions.

The value of GMCS comes from being the integrated combination of two different analytical techniques, gas chromatography and mass spectrometry.

In the following article, we will first introduce them separately and then see how they work in tandem in GMCS testing.

What is Gas Chromatography?

Gas chromatography is a technique for the chemical analysis of substances that can be used independently but, in GMCS Testing, it is part of the first phase of the analytical process.

It was invented in 1941 by Archer John Porter Martin and Richard Laurence Millington Synge.

The sample to be analyzed, which is usually a mixture of different substances, is vaporized, turning it into a gas. 

Next, the gas is injected into a thin tube called a chromatography column, which is filled with a material that acts as a filter, trapping some chemicals longer than others.

Using a laboratory oven, the column is heated in a controlled manner to separate the chemicals. At different temperatures, some substances will pass through the column faster, while others will take longer. 

As the chemicals pass through the column, they are detected by a device called a detector, which records their passage. To identify them, the amount of light absorbed or the amount of electrical charge generated by the chemicals is measured.

The whole process already allows for a good degree of analysis, but combined with mass spectrometry, the results are even more remarkable.

Run Extreme Tests

Discover the new series of Environmental Chambers for controlled climate testing. Find out more.

What is Mass Spectrometry?

Mass spectrometry is the second step in the GMCS Testing process, although it is a technique that can also be used independently.

Within the GMCS Testing process, the sample exits the gas chromatograph and enters the mass spectrometer.

The mass spectrometer itself consists of an ionization chamber, a mass analyzer and an ion detector; all kept under high vacuum by diffusion pumps supported by molecular pumps.

As the sample passes through the ionization chamber, each substance it is composed of is transformed into small charged particles called ions.

The ions generated in the mass spectrometer are then separated based on their mass and charge. This occurs within an area called the mass analyzer. Each chemical produces a unique mass spectrum, which represents the distribution of ions based on their mass.

This allows for extremely precise analysis, capable of identifying each substance with certainty by comparing it with data present in the database containing the known mass spectra of various chemical substances.

Can't find the perfect chamber for your rehearsals?

Build your environment directly online, based on your specific needs. Find out more.

FDM Laboratory Furnaces for GMCS Testing

We have seen that the laboratory furnace plays an essential role in the first phase of the GMCS Testing process.

FDM laboratory furnaces provide the precision and stability needed to superheat the mixture for gas chromatography. 

For further information, please do not hesitate to contact us.

Do you need a quote or have questions about the product?

Contact us for more information about this product. Contact Us

Reference Standards

• ISO 6142-1 — Gas analysis – Preparation of calibration gas mixtures – Part 1: Gravimetric method for Class I mixtures.
• ISO 6145 (series) — Gas analysis – Preparation of calibration gas mixtures using dynamic methods (mass-flow controllers, diffusion, permeation).
• ISO 10723 — Natural gas – Performance evaluation for analytical systems.
• ASTM D1945 — Standard Test Method for Analysis of Natural Gas by Gas Chromatography.
• ASTM D7164 — Standard Practice for On-line/At-line Heating Value Determination of Gaseous Fuels by Gas Chromatography.
• ISO 16664 — Gas analysis – Handling of calibration gases and gas mixtures – Guidelines.
• EN ISO 6974 — Natural gas – Determination of composition and associated uncertainty by gas chromatography.

Authoritative Sources

• ISO – International Organization for Standardization. Publishes ISO 6142/6145/6974 series for the preparation and analysis of calibration gas mixtures.
• ASTM International. Standard D1945/D7164 for Gas Chromatography of Natural Gases and Industrial Mixtures.
• TheNIST Gas Metrology Groupprovides gaseous Standard Reference Materials (SRM) for primary calibration of GMCS systems.
• INRIM – National Institute for Metrological Research. Italian metrological institute for traceability of gas concentration scales.

Frequently Asked Questions about GMCS Testing

What is a Gas Mixture Conditioning System and what is it used for?

A Gas Mixture Conditioning System (GMCS) is a system for preparing and dynamically conditioning gas mixtures with controlled composition, pressure, temperature, and humidity. It typically integrates 2-12 high-precision Mass Flow Controllers (MFCs) (±0.5% of reading, range 1:50-1:100), static or dynamic mixers, bubble or permeation humidification systems, and PID thermostatting of the gas line. Main applications: gas sensor calibration (O₂, CO₂, NOx, VOC, CH₄), fuel cell reliability testing, catalyst characterization, automotive emissions testing, and environmental analyzer validation. Dynamic preparation according to ISO 6145 allows concentrations from ppb to percent with typical uncertainty of 1-3% for dilution factors up to 10⁶.

What is the accuracy of a mixture prepared with GMCS vs. gravimetric cylinder?

Primary gravimetric mixtures according to ISO 6142-1 achieve uncertainties U (k=2) of 0.1-0.5% relative but have a fixed composition and high cost (€500-2000/cylinder). A dynamic GMCS allows for real-time composition variability with typical uncertainty of 1-3% depending on the quality of the MFCs, linearity, and cross-sensitivity effects. For high-accuracy metrological calibration applications, ACCREDIA-calibrated thermal MFCs (uncertainty 0.2%) or Coriolis flowmeters (0.1%) are used. The mixing cycle typically requires 3-10 line volumes for stabilization, equivalent to 30 seconds-5 minutes depending on the volumes. The lines must be made of electropolished stainless steel (Ra ≤ 0.4 μm) to minimize adsorption of reactive species such as NO₂, SO₂, NH₃.

How do you manage humidity in a GMCS for sensor testing?

Controlled humidification uses three methods: (1) bubbler with thermostatically controlled water, simple but with uncertainty ± 5% RH; (2) permeation tube with PTFE/silicone tube at controlled temperature ± 0.1 °C, constant release with uncertainty ± 2% RH; (3) dew-point mixing with a two-temperature generator (saturation + adiabatic expansion) for uncertainties 0.5-1 °C dew point, equivalent to 1-2% RH. The line temperature should be maintained at least 5-10 °C above the dew point to avoid condensation. Electrochemical and NDIR sensors show humidity cross-sensitivity of the order 2-10% per decade of RH, making conditioning critical for reliable testing according to ISO 10723.

What types of gases are typically tested for and what are the safety risks?

Common mixtures include calibration gases (N₂, Ar, He as diluents; CH₄, C₂H₆, C₃H₈ for hydrocarbons; H₂, CO, CO₂, O₂, NO, NO₂, SO₂, H₂S, NH₃ for emissions and industrial processes). Critical hazards: flammability (H₂ LEL 4% vol, CH₄ LEL 5%, requires ATEX 2G or 1G classification), toxicity (H₂S TLV 1 ppm, NO₂ TLV 0.2 ppm, CO TLV 20 ppm), asphyxiation (O₂ < 19.5% in closed environment). The GMCS must operate in a ventilated gas cabinet with 10 gas changes/hour, redundant gas detectors (catalytic + infrared for hydrocarbons, electrochemical for toxics), automatic flow shutoff upon alarm, and fail-safe pneumatic valves. The chemical compatibility of gaskets (Viton, PFA, Kalrez) must be verified for each gas to prevent degradation and leaks.