What Is GC Analysis?
Gas chromatography is a separation technique based on vaporisable components moving at different speeds along a column in a carrier gas stream. Components leave the column at different times; the detector at the column outlet produces a peak for each component. The peak's elution time identifies the component, and its area gives the quantity.
Purpose of GC Analysis
The purpose is to separate the volatile components of a mixture from one another and determine each individually. In GC without a mass spectrometer, identification relies on having the same retention time as a known standard, so the method requires a comparison standard.
Which Products Is GC Analysis Applied To?
- Pharmaceutical and packaging materials tested for residual solvents
- Fuel, oil and petrochemical products
- Fatty acid composition in food
- Volatile organic compounds in paints, adhesives and coatings
- Indoor air and emission samples
In Which Sectors Is GC Analysis Used?
Standards Related to GC Analysis
- ISO 6974 (composition determination in natural gas — gas chromatography)
- ASTM D3710 / D2887 (boiling range distribution in petroleum products)
- ISO 12966 (fatty acid methyl esters in fats and oils)
- VDA 277 (volatile compounds in automotive interior materials)
GC Analysis Conditions
- Column and temperature program
- From the applied method standard; is selected according to the analyte group
- carrier gas
- Helium, hydrogen or nitrogen — defined in the method
- detector
- FID, TCD, ECD or similar; by analyte type
- Enjeksiyon
- Split / splitless / headspace — by matrix
Equipment for GC Analysis
- Gas chromatograph and temperature-programmed oven
- Capillary columns
- FID / TCD / ECD detectors
- Headspace or automatic injection unit
- Carrier gas line and purifiers
Sample Requirements for GC Analysis
- A sample that is volatile, or can be made volatile by derivatisation, is required
- Solvent extraction or headspace is applied for solid and viscous samples
- Sample quantity varies by matrix; a few grams or millilitres is generally sufficient
- Must be sent in a sealed container due to the risk of loss of volatiles
- The sample's known components and suspected analytes must be stated
Duration of GC Analysis
A single chromatographic run is generally under an hour. Total duration is determined by sample preparation, derivatisation and the calibration series; a few working days is typical for routine analyses.
GC Analysis Procedure
- 1The sample is prepared appropriately for the matrix (extraction, dilution, derivatisation or headspace).
- 2Calibration standards are prepared and a calibration curve is built.
- 3The sample is injected onto the column and the temperature programme is applied.
- 4The detector signal is recorded to obtain a chromatogram.
- 5Peaks are identified by retention time.
- 6Peak areas are converted to concentration using the calibration curve.
- 7Quality control is performed using recovery and blank sample results.
GC Analysis Acceptance Criteria
A method produces a result; it does not set a limit. Whether the result is acceptable is determined by the regulation or specification the product is subject to.
Evaluation of Results
Results are calculated from the calibration curve. In a laboratory where the method has been validated, linearity, recovery, repeatability and the limit of quantification are established beforehand; the value in the report is meaningful within this validated range.
GC Analysis Report
- Sample description, receipt date and laboratory number
- Method applied and reference standard, if any
- Instrument and measurement conditions
- Sample preparation steps
- Measurement results and units
- Measurement uncertainty (if requested)
- A statement that the results relate only to the sample submitted for testing
Accreditation
EUROLAB holds internationally recognised accreditation obtained from accreditation bodies party to the IAF and ILAC multilateral recognition arrangements, under ISO/IEC 17025 for laboratory testing, ISO/IEC 17020 for inspection and surveillance, and ISO/IEC 17021-1 and ISO/IEC 17065 for system and product certification. This chain ensures the reports and certificates issued are accepted worldwide.
Whether this test can be offered within accredited scope depends on your product and the standard applied; since accreditation is method-based, the scope is confirmed in writing at the quotation stage.
Scope and authorisationsRelated Regulations
- ICH Q3C (residue solvents in pharmaceuticals)
- EU 1223/2009 Cosmetics Regulation
- Turkish Food Codex contaminants and residue communiqués
Pages Where This Method Is Used
Analytical Methods — What Does This Group of Methods Do?
The section below describes the field that the GC Analysis test belongs to; the conditions and acceptance criteria of this particular test are given in the sections above. The scope specific to your product is confirmed in writing at the quotation stage.
Analytical method pages are pages about a MEASUREMENT TECHNIQUE rather than about a test. The difference matters: "salt spray testing" is a test and answers one question; "ICP-MS" is a technique and is used in dozens of different tests. Sometimes the user is looking not for the test but for the technique — because the method name is what appears in their specification.
This distinction becomes decisive in choosing a laboratory. When a customer asks for "heavy metal analysis", the real question is by which technique it will be done: XRF is fast and non-destructive but does not distinguish compounds; AAS is economical for a single element; ICP-OES screens multiple elements; ICP-MS sees trace levels. The same sample gives results with different detection limits and different uncertainties across the four techniques.
Method selection is made against three criteria. DETECTION LIMIT: is the concentration sought within the range the method can see? MATRIX COMPATIBILITY: is the sample matrix (plastic, food, soil, metal) one the method can handle, and is pre-treatment required? SPECIFICATION LINK: does the product standard or legislation mandate a particular method? The third often overrides the first two — the specification binds the method.
Method pages build a CHAIN. A technique is linked to the test pages where it is used, to the standards those tests rest on, to the legislation those standards are tied to and ultimately to market access regimes. The example chain in the source document works like this: XRF → metal analysis → RoHS compliance → heavy metal restriction → coating pages. Whichever link the user enters from, they reach the others.
Sample preparation is the invisible half of the result in this family and is a greater source of error than the technique itself. The digestion method, degree of grinding, extraction solvent and dilution ratio change the result markedly. The same sample on the same instrument gives a different result with different preparation; the definition of the method therefore covers preparation too.
Calibration and verification are the third determining component. An instrument is calibrated with certified reference material, the calibration curve is verified periodically and a control sample is run in each batch. Without these steps, a number produced is not traceable even if the instrument is working correctly.
Method groups in this field
Elemental analysis
ICP-OES, ICP-MS, AAS and XRF. They differ in detection limit, matrix tolerance and multi-element capacity.
Chromatography
GC, GC-MS, HPLC, LC-MS/MS and ion chromatography. It separates a mixture into its components and measures each separately.
Spectroscopy
FTIR, Raman, UV-Vis and optical emission. For material identity, functional group identification and alloy composition.
Thermal analysis
DSC, TGA, DMA and dilatometry. Transition temperatures, composition, decomposition and dimensional behaviour.
Microscopy and imaging
Optical microscopy, SEM-EDS, radiography and tomography. Structure, defects and elemental distribution.
Classical (wet) chemistry
Titration, gravimetry and colorimetry. Used as a reference method and in confirming instrumental results.
Commonly confused in this field
- XRF is a screening tool; it sees elements and does not distinguish compounds. A decision on a restricted compound requires confirmation by wet chemistry.
- The phrase "not detected" is not proof of absence; it is read together with the detection limit of the method.
- The specification binds the method. A technically better method is not accepted if the specification calls for another.
- Sample preparation is part of the result; a report that does not state the preparation is not reproducible.
- Results obtained by different techniques cannot be compared directly; their detection limits and uncertainties differ.
- A method page is not a test page; which method applies to which test comes from the product standard.
Which decisions these results support
- Matching the method written in the specification to the laboratory's scope
- Method selection according to detection limit and matrix compatibility
- Confirming an instrumental result with a reference method
- Eliminating deviations arising from sample preparation
Related Tests
Frequently Asked Questions About GC Analysis
Can every compound be measured by GC?
No. The compound must be able to vaporise without decomposing. For non-volatile or thermally labile compounds, liquid chromatography techniques such as LC-MS are used.
What is the difference between GC and GC-MS?
It is a difference in detector. In GC, identification relies on retention time and requires a comparison standard; in GC-MS, the mass spectrum gives a compound-specific fingerprint, so unknown compounds can also be identified.