Chromatography is one of the most active and practical research fields in analytical chemistry. Its high sensitivity and high separation efficiency make chromatography an ideal separation and quantitative analysis tool. However, chromatography is relatively inefficient for qualitative analysis. The main basis of the chromatographic method for qualitative analysis is retention value, so it is difficult to make qualitative judgments on unknown components.
Infrared spectroscopy can provide extremely rich molecular structure information, has strong structure identification capabilities, and is an ideal qualitative analysis tool. Almost no two different substances have exactly the same infrared spectrum. However, infrared spectroscopy does not have the ability to separate. In principle, infrared spectroscopy can only be used for the qualitative analysis of pure compounds, and it is often useless for mixtures.
Combining these two methods, the chromatograph is equivalent to the pre-separation tool of the infrared spectrometer, and the infrared spectrometer is equivalent to the qualitative detector of the chromatogram. Gas Chromatography-Infrared Spectroscopy (GC-IR) combines the high-efficiency separation ability of gas chromatography and the molecular structure identification ability of infrared spectroscopy, and is an effective method for the analysis of complex mixtures.
Building on GC-IR, the development of Fourier Transform Infrared Spectroscopy (FTIR) overcame limitations of slow scanning and low sensitivity. FTIR enabled real-time monitoring of chromatographic fractions and detection of trace components, paving the way for GC-FTIR and its broader application in modern research and industry.
With the development and maturity of the interference Fourier transform infrared spectrometer, GC-FTIR technology has made significant progress. FTIR has high detection sensitivity and can detect trace components. At the same time, FTIR has a fast-scanning speed, which can simultaneously track and scan gas chromatographic fractions, which overcomes the biggest obstacle of slow scanning speed when chromatogram and infrared spectroscopy are combined. These developments make the combination of GC and FTIR successful and enter the stage of commercial production. GC-FTIR has been widely used in biomedicine, chemistry and chemical industry, metallurgy, energy, environmental protection, and other fields.
The working principle of GC-FTIR is: After the sample is separated by GC, each fraction enters the interface in order of retention time. At the same time, the interference light modulated by the interferometer converges to the interface. Each fraction in the interface selectively absorbs the interference light, and then the interference signal generated is detected by the detector. The computer system stores the collected interferogram information from the detector and obtains the gaseous infrared spectra of the components through the fast Fourier transform. Finally, the molecular information of each component can be retrieved through the library.
The GC-FTIR system consists of four parts: gas chromatograph, interface, fourier transform infrared spectrometer, and computer data system.
The gas chromatograph in GC-FTIR mostly uses a capillary gas chromatograph, which can be equipped with a thermal conductivity detector (TCD), a hydrogen flame ionization detector (FID), etc., whose function is to separate the components in the mixture.
The interface in GC-FTIR is a key part of the combined system. At present, there are two types of commercial interfaces: light pipe interface and frozen trap interface. The frozen capture interface has the advantages of a high signal-to-noise ratio and low detection limit, but it is expensive and cumbersome to operate. The light pipe interface has the advantages of real-time recording, being relatively cheap, and easy to operate, and is still widely used.
In GC-FTIR,a single optical path FTIR is generally used.
Control online operation and collect and process data.
Fig.1 GC- FTIR instrument structure diagram.
High-Resolution Separation Capability
The GC-IR / GC-FTIR system utilizes advanced gas chromatography technology to efficiently separate trace components in complex mixtures. The instrument supports multiple column types, including capillary and packed columns, accommodating samples with varying polarity and boiling point ranges. With high peak capacity and excellent reproducibility, GC-IR ensures accurate identification of each component, providing a reliable data foundation for research and quality control.
Precise Infrared Spectral Structure Identification
Equipped with a highly sensitive FTIR detector, GC-FTIR rapidly acquires infrared absorption signals, enabling precise characterization of molecular structures. This technology is particularly suitable for organic compounds, volatile flavors and fragrances, oils, and chemical intermediates, delivering accurate functional group identification and qualitative analysis. Additionally, real-time spectral acquisition is supported, allowing comprehensive structural information without complex sample pre-treatment, significantly enhancing analysis efficiency.
Complex Sample Analysis Capability
GC-IR / GC-FTIR can handle multi-component mixtures, including trace-level constituents and azeotropes. It provides reliable and reproducible results for complex samples such as flavors and fragrances, petrochemicals, and food volatiles. By combining GC separation with FTIR identification, the instrument enables integrated "component separation + structural confirmation" analysis, greatly improving accuracy and informational value.
High Sensitivity and Quantitative Potential
The detection limit of GC-FTIR reaches microgram to nanogram levels, effectively detecting trace components. Infrared spectral signals exhibit excellent linearity, allowing semi-quantitative or quantitative analysis (using external or internal standards), meeting the requirements of R&D and process optimization. High reproducibility ensures consistent data, making the system equally effective for quality control and batch analysis.
Table.1 Comparison of GC-FTIR and Conventional GC / GC-MS Technologies.
| Feature | GC-FTIR | Conventional GC or GC-MS |
| Functional Group Identification | Accurate and direct; identifies >90% of common functional groups | Indirect or inferred; relies on spectral library, ~70–80% accuracy |
| Sample Compatibility | Broad; capable of analyzing C3–C30 volatile organics, flavors, oils | Limited by ionization efficiency and spectral library; some non-polar or low-volatility samples difficult to analyze |
| Spectral Resolution | High, up to 4 cm-1; can distinguish isomers | Not applicable |
| Data Interpretability | Structure directly corresponds to IR spectral features; easy to interpret | Relies on library matching or experience; structural info is indirect, difficult for complex samples |
| Detection Limit | Microgram to nanogram level; suitable for trace component analysis | Typically microgram level; low-concentration detection limited |
| Reproducibility / Quantitative Capability | High reproducibility; relative standard deviation<3%, supports semi-quantitative or quantitative analysis | Moderate reproducibility; relative standard deviation 5–10%, quantitative analysis requires calibration |
At BOC Sciences, we provide comprehensive GC-FTIR data to support both qualitative and quantitative analysis. Our system delivers detailed chromatographic, spectral, and library comparison information, as well as key quantitative and confirmation metrics to ensure accurate compound identification and characterization. GC-FTIR's data processing system can provide the following information:
The chromatographic retention value can be used as a qualitative auxiliary basis. The chromatographic retention value is very important for compounds with different numbers of repeating units in the molecular structure, such as homologs. These compounds have similar infrared spectral characteristics but different chromatographic retention values.
The GC-FTIR system can provide quantitative parameters such as peak area and peak height, which are used to determine the relative or absolute content of each component. These quantitative data can support the analysis of compositional changes in the sample and can be applied in subsequent quantitative studies and comparisons.
During GC-FTIR library searches, the system can provide match scores or similarity coefficients to evaluate the degree of similarity between the unknown component and reference spectra in the library. These indicators assist in assessing the reliability of compound identification, enhancing the accuracy of qualitative analysis.
The chromatogram obtained by GC-FTIR is called the reconstructed chromatogram, which is the result of computer processing the interferogram recorded by the infrared detector.
The infrared spectrum characterizes the absorption frequency and intensity of each group in the compound molecule. Infrared spectroscopy can be used to identify the molecular structure of the compound.
Comparing the gaseous infrared spectrum obtained by GC-FTIR with the gaseous infrared standard spectrum stored in the computer can confirm the presence of unknown components.
With the continuous development and improvement of GC-FTIR technology, GC-FTIR technology has become an effective means for qualitative and quantitative analysis of complex organic mixtures. GC-FTIR has incomparable advantages in many aspects, especially the separation and identification of isomers. GC-FTIR is widely used in natural product volatile oil (such as medicinal volatile oil analysis), flavor and fragrance analysis, petrochemical analysis, environmental pollution analysis (such as wastewater analysis, air pollutant analysis, pesticide residue detection, toxic substance detection), fuel analysis (coal and petroleum distillate analysis), etc.
GC-FTIR can be used for the separation and identification of raw materials, intermediates, excipients, and impurities in small molecule drugs, and is particularly suitable for the analysis of isomers, stereoisomers, or degradation products. By utilizing chromatographic retention values, reconstructed chromatograms, and infrared spectra, drug components can be accurately distinguished and their molecular structures confirmed. Combined with library search, quantitative data, and qualitative confirmation indicators, GC-FTIR enables comprehensive qualitative and quantitative analysis of drug components.
GC-FTIR is capable of analyzing structurally similar components and derivatives in large molecule drugs, and is suitable for the separation and identification of multi-component mixtures, complexes, and high-molecular-weight drugs. BOC Sciences provides chromatographic retention values, reconstructed chromatograms, and infrared spectra, combined with library search, peak area/height, and match scores, to achieve accurate qualitative and quantitative analysis of large molecule drugs and their impurities.
GC-FTIR is widely applied to the analysis of natural product volatile oils (e.g., medicinal volatile oils), allowing separation of complex mixtures, structural identification, and differentiation of homologous components. By providing chromatographic retention values, reconstructed chromatograms, infrared spectra, and library search, unknown components can be confirmed. Additionally, peak area, peak height, and match scores are provided to enable comprehensive qualitative and quantitative analysis.
In flavor and fragrance analysis, GC-FTIR can separate and identify isomers and complex components of aromatic compounds. By providing chromatographic retention values, reconstructed chromatograms, and infrared spectra, combined with GC-FTIR library search, quantitative data, and qualitative confirmation indicators, reliable identification and content analysis of flavor components can be achieved, supporting formulation optimization and quality control.
In the petrochemical field, GC-FTIR can be used for the component analysis of petroleum distillates, hydrocarbons, and their derivatives, and is particularly effective for separating homologs or impurities. BOC Sciences provides chromatographic retention values, reconstructed chromatograms, and infrared spectra, combined with library search, peak area/height, and match scores, enabling accurate qualitative and quantitative analysis of complex petrochemical mixtures and supporting product quality evaluation and process optimization.
1. Sample Consultation and Plan Confirmation
Clients can submit their sample analysis requests via the website form, email, or phone, providing information on sample type, target analysis, and quantity. Our technical team will review the sample characteristics and analysis objectives and provide a customized analysis plan, including recommended column type, detection mode, analysis timeline, and quotation.
2. Sample Submission and Receipt
Clients prepare samples according to the provided guidelines (sample amount, solvent, packaging, storage conditions) and send them to the BOC Sciences laboratory via secure logistics. Upon receipt, the lab performs sample registration and quality inspection to ensure sample integrity and suitability for analysis.
3. GC-FTIR Analysis
Samples are analyzed using our advanced GC-FTIR system, which combines high-resolution gas chromatography separation with infrared spectral identification. The process includes:
All analyses are conducted by our experienced technical team to ensure accuracy and reproducibility.
4. Data Processing and Report Generation
After analysis, the technical team processes and interprets the raw spectral data to generate a standardized analysis report, which includes:
The report undergoes quality review to ensure completeness, clarity, and applicability for R&D or quality control purposes.
5. Report Delivery and Technical Support
Analysis reports are delivered to clients via email or an online platform. Clients also receive technical support and data interpretation, including result explanation, peak identification, and method recommendations. Upon request, BOC Sciences can provide sample return or long-term data archiving services.
6. Client Feedback and Continuous Optimization
BOC Sciences encourages client feedback to continuously improve service quality and workflow efficiency. For long-term projects, we offer customized analysis packages and periodic reporting, meeting the ongoing needs of R&D and production.
Comprehensive Qualitative and Quantitative Analysis
BOC Sciences provides complete GC-FTIR data, including chromatographic retention values, reconstructed chromatograms, infrared spectra, library search, quantitative information (peak area/height), and qualitative confirmation indicators (match scores/similarity coefficients). This allows clients to perform full-process analysis from component separation to molecular structure confirmation.
Applicable to a Wide Range of Fields
Our GC-FTIR services are suitable for small and large molecule drugs, natural product volatile oils, flavors and fragrances, petrochemical products, and environmental pollutants, providing reliable analytical data for research, quality control, and product development.
High Sensitivity and Isomer Differentiation
GC-FTIR combines the high separation capability of gas chromatography with the molecular structural identification ability of Fourier-transform infrared spectroscopy, enabling precise differentiation of homologs, isomers, and trace impurities, ensuring accurate and reliable results.
Professional Team and Customized Services
BOC Sciences has an experienced analytical team that can provide customized method development, sample analysis, and result interpretation based on the sample type and specific client requirements, ensuring that each dataset meets the needs of research, development, or quality control.
Reliable and Traceable Data
We deliver complete, standardized GC-FTIR data that are easy to review and reproduce, providing clients with traceable, high-quality analytical support for research and production purposes.
How does GC-IR work?
Gas Chromatography-Infrared Spectroscopy (GC-IR) combines the high separation capability of gas chromatography with the structural identification power of infrared spectroscopy. Samples are first separated into individual components by a gas chromatography column. Each component is then transferred through an interface to an infrared detector, which records the characteristic absorption of infrared light, generating a unique spectral fingerprint for qualitative analysis and structural confirmation.
What is the difference between gas chromatography and infrared spectroscopy?
Gas chromatography (GC) is a separation technique used to isolate individual components from a mixture, while infrared spectroscopy (IR) is a structural analysis method that identifies functional groups and molecular structures based on infrared absorption. GC provides "separation information," and IR provides "structural information." Together in GC-IR, they offer both high-resolution separation and molecular structure characterization.
What are the main applications of GC-IR?
GC-IR is widely used for analyzing complex mixtures and structural identification, including natural product extracts, organic synthesis intermediates, flavors and fragrances, volatile organic compounds (VOCs) in environmental samples, and trace components in polymers or materials. It is suitable for qualitative analysis, component confirmation, and trace impurity detection.
Why choose GC-IR services?
GC-IR services allow clients to access high-resolution separation and structural analysis without investing in expensive instrumentation. We provide customized method development, sample preparation, chromatographic optimization, and infrared spectral analysis, ensuring reliable results and reproducibility for complex samples.
What types of samples are suitable for GC-IR?
GC-IR services are ideal for volatile or gasifiable samples, including low-molecular-weight organic compounds, fragrances, solvent residues, VOCs in environmental samples, and gas-compatible natural products or pharmaceutical intermediates. For thermally sensitive or complex multi-component samples, we optimize interfaces and analytical conditions to achieve high-quality infrared spectral detection.
Our gas chromatography–infrared spectroscopy solutions enable precise functional group identification. BOC Sciences offers detailed, accurate characterization for complex samples.
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