Gas chromatography coupled with flame ionization detection , more commonly known as GC-FID , is a widely used analytical technique in laboratories for the detection and quantification of volatile and semi-volatile organic compounds. Precise, rapid, and cost-effective, it has become an essential tool in many industrial sectors, including food processing , cosmetics , pharmaceuticals, environmental monitoring, and petrochemicals. This article provides a comprehensive overview of this method, from its operation to its practical applications, answering the main questions asked by professionals in charge of quality control, R&D, and regulatory compliance.
For a detailed presentation of the technical parameters and equipment, see our page dedicated to GC-FID analysis .
Table of Contents
What is GC technique?
Principle of gas chromatography
Gas chromatography (GC ) is a separation technique used to analyze the volatile components of a mixture. It relies on the migration of gaseous compounds through a column containing a stationary phase. Each compound passes through the column at a different rate depending on its physicochemical properties, including its volatility and affinity for the stationary phase. This difference in transit time, called the retention time , allows the components of the mixture to be separated from one another.
Gas chromatography (GC) is particularly well-suited to the analysis of volatile and semi-volatile organic , such as solvents, hydrocarbons, alcohols, esters, and light organic acids. It is commonly used for both qualitative (identifying the substances present) and quantitative (determining their concentration) purposes.
Typical experimental conditions
A gas chromatography system typically consists of:
- of an injector , where the sample is introduced in liquid or gaseous form;
- of a carrier gas (often helium, sometimes nitrogen or hydrogen), which carries the compounds through the column;
- of a capillary column containing a stationary phase adapted to the nature of the compounds analyzed;
- of an oven , which allows a controlled and sometimes programmed temperature to be maintained according to a heating ramp;
- of a detector , such as the FID, which identifies the compounds at the column outlet.
(5% phenyl)-methylpolysiloxane type column , with helium as carrier gas, will efficiently separate volatile nonpolar such as residual solvents in a cosmetic formulation or organic compounds in a plant extract.
The choice of column temperature , the nature of the carrier gas , and the length and polarity of the column are all crucial parameters that influence the quality of the separation and the reproducibility of the results.
Gas chromatography, while highly effective at separating the components of a sample, cannot by itself precisely identify their chemical nature or measure their concentration. Therefore, it is always coupled with a detector , whose role is to detect and quantify the compounds once separated. The flame ionization detector (FID) is one of the most widely used for this purpose, due to its sensitivity and reliability.
What is a FID detector and how does it work?
The principle of flame ionization
The flame ionization detector, or FID , is a detector commonly used at the outlet of a gas chromatography system. Its purpose is to detect and quantify carbon-based organic after their separation in the chromatographic column. Its operation is based on a simple and highly effective principle: the ionization of molecules in a flame .
In practice, the compounds separated by GC are fed into a flame produced by a mixture of hydrogen and air. When a carbon-based passes through this flame, it is partially burned, generating ions and electrons . These charged particles are then collected between two electrodes positioned around the flame, generating an electric current proportional to the amount of carbon in the compound. This current is converted into a analytical signal , which can be used to quantify the concentration of substances present in the sample.
This mechanism explains why FID is particularly sensitive to organic compounds containing carbon-hydrogen (CH4). Conversely, compounds that do not contain carbon, such as water (H₂O), carbon dioxide (CO₂) or nitrogen (N₂), are not detected by FID, which constitutes one of its limitations but also an advantage in terms of selectivity towards target compounds.
Sensitivity, specificity and limitations of the FID detector
The FID detector has several major advantages which explain its widespread use in the laboratory:
- High sensitivity : FID is capable of detecting traces of organic compounds , with detection limits ranging from a few nanograms to a few picograms , depending on the analytical conditions.
- Very good linearity : the FID response is linear over a wide range of concentrations, which facilitates quantitative assays.
- High reproducibility : the technique gives very stable results from one analysis to another, which is essential for quality control measurements.
- Robustness : the system is simple to maintain, not very sensitive to contaminants and works reliably over long series of analyses.
However, the FID is not a universal detector. It has several limitations :
- It cannot identify compounds structurally: it gives no information on the precise chemical nature of a compound (unlike a detector such as a mass spectrometer).
- It does not detect inorganic compounds or without carbon atoms .
- It requires a perfectly adjusted and safe gas system (hydrogen and air), due to the presence of a flame.
Despite these limitations, FID remains one of the most widely used detectors in the laboratory , particularly for applications where quantifying organic compounds takes precedence over their detailed identification. This is why FID is frequently preferred in industrial settings requiring purity analyses , residual solvent detection , or regulatory compliance measurements .
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What is the difference between GC and FID?
GC: a method for separating compounds
Gas chromatography (GC) is a separation technique that allows the analysis of the components of a complex mixture by separating them according to their volatility and their interactions with the stationary phase of a chromatographic column. This method is based on the principle of the distribution of compounds between a mobile phase (the carrier gas) and a stationary phase (fixed inside the column). Each component of the mixture takes a different time to pass through the column, depending on its physicochemical properties.
The retention time , measured for each compound, allows us to obtain a chromatogram : a graph where each peak corresponds to a separate compound. However, this chromatogram is only a temporal distribution diagram. At this stage, we know that there are several compounds in the sample and we know their transit times in the column, but we cannot formally identify them or quantify them precisely without a coupled detection system.
Thus, GC acts as a very efficient sorting system, but does not, on its own, allow us to conclude on the nature or quantity of the substances analyzed.
FID: a detector for quantifying separated compounds
The flame ionization detector (FID) is a detection instrument used at the GC output. While GC separates the constituents, the FID then detects and measures the carbonaceous organic compounds at the column outlet. It does not replace GC, but complements by providing a quantitative measurement of the signal obtained.
Each peak observed on the chromatogram corresponds to a separate compound, the peak area is proportional to its concentration . FID is therefore an ideal tool for the precise quantification of substances in a sample. It allows us to answer questions such as: What is the residual concentration of this solvent in the finished product? or Does this batch conform to analytical specifications?
The great strength of the GC-FID combination therefore lies in the complementarity between the two tools:
- GC allows the separation of dozens of volatile compounds present in a complex mixture;
- FID allows each compound to be quantified separately in a reproducible and sensitive manner.
Comparison with other detection systems
There are several types of detectors that can be coupled to gas chromatography. Here is a comparative overview with FID:
- FID vs. MS (Mass Spectrometry)
: MS is a very powerful detector that allows the structural identification of compounds based on their mass-to-charge ratio (m/z) . It is suitable for the search for unknown substances or for reformulation, but it is more complex, more expensive, and less robust than FID. FID, on the other hand, is simpler , more stable , and faster to implement , making it ideal for routine quantitative measurements . - FID vs. TCD (Thermal Conductivity Detector):
The TCD is a universal detector, capable of detecting both organic and inorganic compounds. However, it is less sensitive than the FID for carbon compounds, which limits its use to higher concentrations.
The choice between FID and other detectors therefore depends on the specific analytical need : structural investigation, quantitative measurement, trace analysis, robustness in routine use, etc. In practice, FID remains one of the most widely used in industrial laboratories for quality control, regulatory compliance checks, and process optimization.
GC-FID coupling: an essential technique in analytical chemistry
Why use GC-FID in the laboratory?
The coupling of gas chromatography (GC) with a flame ionization detector (FID) has become a reference method in analytical chemistry , thanks to its simplicity, reliability, and efficiency. It is a versatile tool used to identify and quantify organic compounds in a wide variety of matrices.
The GC-FID offers several decisive advantages :
- Excellent sensitivity to carbon-based organic compounds, with low detection limits (on the order of nanograms).
- High robustness in routine use : the analysis is not very susceptible to interference, easy to automate and reproducible.
- Linear response over several orders of magnitude , which facilitates the construction of reliable calibration curves for dosing.
- Short analysis times , generally from a few minutes to about thirty minutes depending on the complexity of the sample.
- Cost is controlled compared to other techniques such as GC-MS, which is more expensive in terms of equipment and data processing.
This combination of characteristics makes GC-FID a technique particularly well-suited to routine analyses, compliance testing, quality control, or applied research . It is widely used in industry to validate the purity of raw materials , verify the conformity of finished products , or identify anomalies in a production process.
Typical applications of the GC-FID method
The GC-FID method is implemented in numerous industrial and environmental fields. Here are some concrete examples of analytical applications where it is commonly used:
- Residual Solvent Analysis:
In cosmetic, pharmaceutical, and food products, it is essential to verify that the solvents used during manufacturing (ethanol, isopropanol, hexane, etc.) are present only in trace amounts. GC-FID allows for their precise detection and quantification , in accordance with regulatory standards (e.g., ICH Q3C). It also enables the detection of organic contaminants in sensitive matrices such as cosmetics and food products. - Determination of Phthalates and Hydrocarbons:
Phthalates, often used as plasticizers, can migrate into finished products. Their determination by GC-FID is a frequent requirement under the REACH regulation or for the control of food packaging. Similarly, aliphatic or aromatic hydrocarbons can be detected in oils, lubricants, or processing products. - Purity control of substances
When a raw material or active ingredient is expected to contain a single substance, GC-FID makes it possible to verify the absence of impurities or manufacturing by-products. - Deformulation of complex polymers or mixtures
By coupling GC-FID with complementary devices (extraction, headspace or pyrolysis ), it is possible to characterize the volatile components of a polymer or a formulated mixture, particularly useful in the context of reverse engineering . - Industrial process monitoring
In petrochemical, agri-food or environmental sectors, GC-FID is used to monitor changes in the composition of gases, solvents or fermentation products over time.
Widely adopted in quality control, R&D and regulatory compliance laboratories, GC-FID is therefore a reliable, fast and accurate , suitable for many use cases.
To learn more about methods for characterizing complex mixtures, check out our article: Deformulation: how to identify the components of a complex product?
What are the steps involved in a GC-FID analysis in the laboratory?
Sample preparation
The first step in a GC-FID analysis is sample preparation , which must be adapted to its physical nature (liquid, solid, or gas) and the analytical target. Careful preparation is essential to guarantee the quality, accuracy, and reproducibility of the results.
- For liquids : the sample is generally diluted in a solvent compatible with the chromatographic column and detector (e.g., methanol, acetone, hexane). It is then injected directly via a micro-syringe into the GC system injector.
- For gases sealed syringes or specific bags are used to collect and introduce samples into the GC system. This prevents any loss or contamination.
- For solids extraction step is often necessary. This can be carried out by liquid/solid extraction , by headspace (analysis of the gas phase above the solid sample), or by pyrolysis , which consists of heating the solid to release its volatile constituents.
In all cases, calibration standards are added to allow for the quantification of the detected compounds. These standards can be provided by the laboratory or by the client, depending on the method requirements.
Configuration and injection
Once the sample is prepared, the GC-FID system is parameterized according to the expected characteristics of the compounds to be analyzed.
- Column selection : the nature of the stationary phase must be adapted to the polarity of the compounds. For example, for nonpolar molecules (hydrocarbons, solvents), a (5% phenyl)-methylpolysiloxane .
- Oven temperature : a temperature program is defined, either isothermal or ramped, to optimize the separation of chromatographic peaks.
- Carrier gas : Helium is often used for its performance and compatibility with FID, but other gases such as nitrogen can be used.
- Injected volume : generally between 0.1 and 2 µL, depending on the concentration and type of sample.
The sample is then injected into the system through the heated injector, vaporized, and then carried by the carrier gas into the column where the separation takes place.
Interpretation of results
Once the compounds are separated and detected by the FID, the data is translated into a chromatogram . Each peak corresponds to a compound , and its area is proportional to its concentration .
- Compound identification : identification is done by comparison with retention times of known standards or using databases.
- Quantification : the concentration of compounds is calculated from calibration curves, constructed with standards of known concentrations.
- Validation of results : the data are then validated according to the quality standards (ISO 17025, GLP, etc.), with control of the parameters of reproducibility, precision, accuracy and linearity.
The final report mentions the measured values , units , detection limits , and regulatory compliance (e.g., regulatory thresholds for phthalates, solvents, or other restricted substances).
These standardized steps ensure rigorous and reliable analysis , tailored to industrial, regulatory, or R&D requirements. The entire process can be managed via the YesWeLab platform, which centralizes sample management, partner laboratory selection, and results tracking.
How does GC-FID fit into analytical protocols?
Analytical methods based on matrices
In the laboratory, the GC-FID method is selected according to the type of matrix to be analyzed and the objectives of the analysis. It is particularly suited to volatile or semi-volatile in complex matrices such as food, cosmetics, polymers, technical solvents or environmental samples.
- Cosmetics : GC-FID allows for the quantification of residual solvents (e.g., ethanol, isopropanol) present in perfumes, lotions, or creams. These compounds often need to be monitored for safety reasons and regulatory compliance (Regulation 1223/2009).
- Food : The analysis of volatile fatty acids , flavorings , or solvent residues in processed products can be performed rapidly by GC-FID. For example, in confectionery, GC-FID is used to verify the conformity of the flavor profile or to detect the presence of organic contaminants.
- Polymers : In combination with a pyrolyzer or headspace cell, GC-FID allows the analysis of compounds released during the thermal degradation of plastics or composite materials. This approach is useful for identifying additives, monomer residues, or polymerization byproducts.
Importance of standards and accreditations
All laboratory analyses must adhere to strict quality and traceability standards . The GC-FID method, like other analytical techniques, is often implemented within the framework of regulatory or sector-specific guidelines.
- ISO 17025 : This international standard defines the technical competence requirements for testing and calibration laboratories. It guarantees the reliability, reproducibility, and traceability of results. GC-FID analyses performed under ISO 17025 accreditation are therefore recognized by regulations .
- COFRAC : In France, laboratories accredited by COFRAC offer an additional guarantee of quality and compliance. This is particularly important for analyses intended for regulatory controls, certifications, or the compilation of technical dossiers (REACH, cosmetics regulations, food safety, etc.).
The rigorous application of these standards ensures that the results provided are scientifically valid , legally usable , and internationally comparable .
Material migration and conformity testing
One of the most frequent regulatory applications of GC-FID concerns migration tests performed on materials that come into contact with food. These tests aim to ensure that the materials do not release harmful substances into the food.
According to EC Regulation No. 1935/2004 , materials and articles intended to come into contact with food must be designed so as not to transfer components that could pose a danger to human health or alter the organoleptic characteristics of the food. GC-FID is used for:
- quantify the phthalates (banned or restricted plasticizers) that may migrate from plastics,
- to measure the residual solvents present in printing inks or adhesives,
- analyze volatile organic compounds (VOCs) that may migrate from packaging into food.
These tests must also comply with the requirements of health authorities outside the EU, such as the FDA in the United States. They are part of quality control, conformity validation, or supplier qualification plans.
Rheological tests and interaction with other techniques
Although GC-FID does not directly measure physical properties such as viscosity or texture, it is often complementary to other methods in multidisciplinary laboratories. For example, in a rheological test designed to analyze the texture of a cosmetic cream, GC-FID can be used to:
- detect the degradation of volatile agents responsible for texture,
- to measure the variations in composition that influence the consistency of the product.
In general, GC-FID is often integrated into comprehensive analytical protocols , alongside techniques such as HPLC , UV-Vis spectrophotometry , or thermal analysis . It plays a central role in evaluating the chemical quality of products, complementing physical or microbiological performance analyses.
This complementarity between approaches makes it possible to obtain a complete characterization of the samples, essential to guarantee the safety, stability and regulatory compliance of the products analyzed.
Why choose YesWeLab for your GC-FID analyses?
A fast, centralized, multi-laboratory solution
Choosing YesWeLab for your GC-FID analyses means benefiting from a network of over 200 partner laboratories in France and Europe, all selected for their expertise and compliance with quality standards (ISO 17025, COFRAC, GLP, etc.). Thanks to its intuitive digital platform , YesWeLab allows manufacturers to centralize all their analytical needs in a single point of contact, whether for one-off analyses, quality control campaigns, or complex R&D projects.
YesWeLab's multi-laboratory approach offers several advantages:
- Save time : search, selection, contact and quotes are managed in a centralized and simplified manner.
- Access to specialized expertise : some laboratories are dedicated to polymers, others to cosmetics, and still others to environmental or pharmaceutical analyses.
- Reduced processing times : thanks to a dense network and optimized management, analysis times are reduced without compromising on quality.
GC-FID is a widely used method but with variable technical parameters (column, polarity, sample preparation…), so YesWeLab quickly identifies the most suitable laboratory according to your matrix, your analytical objective and your regulatory constraints.
Various sectors covered
YesWeLab operates in more than ten industrial sectors and has partner laboratories specializing in each of them. Here are some concrete examples of GC-FID analyses commonly performed:
- Food processing : control of residual solvents in flavorings or packaging, measurement of volatile fatty acids, verification of the conformity of essential oils.
- Cosmetics : detection of prohibited or restricted substances (phthalates, solvents), purity control of raw materials.
- Pharmaceutical : analytical validation of volatile active ingredients, analyses according to ICH Q3C guidelines on residual solvents.
- Materials and polymers : characterization of volatile compounds released during manufacturing or thermal degradation, post-pyrolysis analysis.
- Environment : detection of volatile organic compounds in air, effluents or leachates.
This sectoral versatility allows YesWeLab to offer tailor-made analyses, adapted to the regulations specific to each field (REACH, regulation 1223/2009, pharmacopoeia, EC 1935/2004, etc.).
Personalized support and actionable results
YesWeLab does not limit itself to connecting you with a laboratory: its team supports you throughout the analytical process , from defining the need to interpreting the results.
- Analysis of technical and regulatory needs : choice of analytical parameters, standards to be respected, type of validation desired.
- Preparation of the analytical specifications : description of the matrices, nature of the target compounds, expected detection limits.
- Digital project monitoring : traceability of samples, announced deadlines, secure provision of analysis reports.
Analytical consulting services can also be offered to help you interpret the results or guide a quality control or compliance strategy.
