Analysis of technical hexane by Headspace GC-MS: control of matrix effects and false positives
SUMMARY OF THE INTERVENTION
1. Technical hexane: an industrial solvent under analytical surveillance
Technical hexane is a nonpolar solvent widely used for industrial extraction of fats. It consists of a complex mixture of C6 hydrocarbons, including several hexane isomers, among which n-hexane is of particular interest from an analytical and toxicological point of view.
The determination of hexane residues in food matrices, at very low concentrations, requires robust, sensitive, and well-characterized analytical methodologies.
2. Headspace GC-MS: a method suitable for volatile compounds
Gas chromatography with static headspace sampling (Headspace GC) is widely used for the analysis of volatile hydrocarbons. This technique limits sample handling and is particularly suitable for nonpolar compounds.
While flame ionization detection (FID) has historically been used, quantification at very low levels—down to approximately 0.05 mg/kg—now requires detection by mass spectrometry (GC-MS), which ensures better selectivity and reliable identification of compounds.
3. Matrix effects: a major challenge at low concentrations
At low concentration levels, the main methodological limitation of headspace analysis lies in matrix effects.
The principle is based on the distribution of volatile compounds between the condensed phase and the gas phase, an equilibrium that is strongly influenced by the composition of the matrix. In food matrices rich in lipids, this phenomenon can significantly alter the transfer of hexane to the headspace, impacting the analytical response and increasing measurement uncertainty.
Furthermore, interference from the matrix or the environment can cause chromatographic or spectral overlap, increasing the risk of false positives when signals are close to the detection limits.
4. Towards robust and reliable methods for trace analysis
The objective of this presentation is to introduce the analytical principles of static headspace sampling, evaluate the impact of matrix effects on quantification and identification, and discuss methodological approaches for controlling these phenomena.
The work carried out at ITERG has made it possible to define:
- optimized Headspace conditions
- calibration strategies tailored to matrices
- enhanced identification criteria
These optimizations enable the development of robust, sensitive, and reliable Headspace GC-MS methods for the determination of technical hexane in trace amounts.
Contact: h.griffon@iterg.com