Comparison of two methods based on dynamic head-space for GC-MS analysis of volatile components of cheeses

Summary Two methods based in dynamic headspace sampling have been compared for GC/MS analysis of volatile components in hard cheeses (Manchego and other ewe’s milk varieties). In the first approach a purge & trap concentrator allowed volatile on-line determination with reduced sample handling. The second method consisted of a manual device for trapping dinamically purged volatiles, which were then anaysed by using an automatic thermal desorption system, coupled on-line with a GC-MS. The influence of the most significant operating parameters (desorption times, flows and temperatures) on recovery and repeatability was studied for both methods. Automatic purge & trap gave the best sensitivity and repeatability for high valatility components, probably because its on-line operation mode, while the second procedure allowed the determination of a greater number of volatile components and gave better yields for fatty acids and other medium volatility components.