Retention time locked methods and databases simplify analysis of the complex mixtures found in essential oils and flavours
For many years, gas chromatography (GC) using capillary columns has been the analytical method of choice for the analysis of essential oils.
However, because of the complexity of essential oils, there is no single GC capillary column that can resolve all possible compounds.
Spectral data from gas chromatography/mass spectrometry (GC/MS), another popular technique, is not always conclusive because isomers give similar spectra.
Therefore, in flavour and fragrance quality control, indices of retention times for analytes of interest are frequently used to complement capillary GC.
When analytes of interest elute from an analytical column, retention times can depend significantly on column type, temperature programme, and carrier gas velocity.
Recent developments in GC have made it possible to lock retention times so that results are the same from run to run, operator to operator, and laboratory to laboratory.
Consequently, absolute retention time can be used as an identification tool, making this an excellent QA/QC tool for essential oils and flavours.
Agilent application chemists, in cooperation with Quest International in the Netherlands, developed two retention time locked methods. Each method includes a database of retention times containing approximately 400 flavour compounds and essential oil constituents.
The first is a GC/flame ionisation detector method particularly useful for quality control analyses; the second is a GC/MS method that matches retention times and mass spectral data to identify essential oil constituents.
Agilent chemists also found that, under specific operational conditions, retention indices from existing retention index libraries can be transferred into locked retention time databases.
Further, a retention time locked database can work with any GC detector.
For further information, request Agilent application note 'Analysis of essential oil compounds using retention time locked methods and retention time databases', Agilent publication number 5988-6530EN.
This note is available without charge from any Agilent sales office or its website.
