Static Headspace Gas Chromatography (HS-GC) is a relatively special analysis technique in which a gas (or vapor) sample is taken in the top space of a liquid or solid analyte in a closed container at equilibrium and analyzes the gas (or vapor) samples when combined with vapor chromatography. The main advantage of top-air state sampling is to avoid the possibility that the complex sample matrix components are brought into the analytical instrument system together during direct liquid or solid sampling, thus eliminating the influence and interference of the analysis of the volatile components in the sample caused by the introduction of the matrix components.
I. Application fields: Agriculture and food science, pharmacology and pharmaceutical analysis, criminal law medicine and environmental analysis, the focus on the transformation technology of samples.
II. Determination technology:
Conventional headspace analysis technology: the two-phase balance of the measured substance in the gas-liquid or gas-solid phase;
Full evaporation headspace analysis technology: full evaporation (full evaporation, FE) headspace technology is the headspace sample container (bottle) as an evaporator and realize the sample of volatile composition quantitative analysis technology (organic sulfur compounds such as methyl thiol, dimethyl sulfide and dimethyl disulphide content determination, methyl methacrylate polymer emulsion (containing high polymer, monomer and aqueous phase) residual monomer content determination);
Chemical reaction type headspace analysis technology: the acidification of samples to determine the content of carbonate and sulfide, the determination of the carboxyl content in wood fiber, a very small amount of acid or alkaline material content determination;
Tracer top-air chromatography technology: Using the "exclusion" or "adsorption" of volatile tracers by the measured components in the sample (solubility determination of inorganic salts, micro-organic adhesives, monomer solubility, etc.)
Multiple headair extraction technology: multiple headair extraction (multiple headspace extraction, MHE) is similar to the dynamic headair extraction phase.
III. Summary:
The GC method based on headspace sampling can not only omit or simplify the analytical sample preprocessing steps, but also broaden the application scope of GC analysis. Different from conventional analytical instruments, the automatic headspace sampler combined with gas chromatography has unique temperature control, sample bottle shaking, repeated headspace sampling and time control functions, which can make many tested samples in the ceiling sample bottle conditioning, or simulate the desired chemical reaction, so as to achieve direct or indirect determination. It can be believed that due to the uniqueness and further development of the technology, top-air chromatography will play a greater role in future scientific research and practical applications.
