A headspace analyzer is used for testing the volume of oxygen and carbon dioxide inside packaging such as food, drink, medicine and other packaged products. It is an important part of Quality Control for Modified Atmosphere Package (MAP) products and helps ensure that the atmosphere inside the package complies with predefined limits to avoid oxidation and spoilage.
A sample is headspace analyzer in a vial, sealed and heated to a specific temperature. The volatile components that are less volatile at or below this temperature escape from the vial to form a gaseous headspace. The headspace is analyzed using gas chromatography with a mass selective detector to identify the components.
Static Headspace Analysis (SHS) is a common method for analyzing volatile compounds in liquid and solid samples. It is based on the concept that volatile analytes can diffuse into the headspace at a temperature-dependent rate. The concentration of the analyte in the headspace is determined by calculating the partition coefficient of the analyte between the sample and the headspace, which is proportional to the temperature of the sample.
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The headspace is measured by a sampling probe that pierces the vial, with a heated sampling valve and loop. The sampling probe is purged to remove any residual air, then the headspace is sampled into a trap to concentrate the outgassed material for analysis by GC/MS. This method can be a time-consuming process and requires multiple aliquots from each sample, but it is highly accurate with low detection limits and works well with samples with high levels of interfering matrix.