• gut microbiota
• HiSorb
• pentaflorobenzyl bromide
• saliva
• short-chain fatty acids
• TD-GC-MS/MS
• thermal desorption

Saliva analysis, already known as unconventional biological fluid, offers numerous advantages for the study of interesting analytes from a clinical and pharmacological point of view compared to classic blood samples. In this context, the work included both the development and validation and optimization of an analytical method for the determination of short-chain fatty acids (SCFAs) within the salivary matrix. Among these there are some of the most interesting compounds such as acetic, propionic and butyric acid. These compounds are the products of the fermentations of fibers and carbohydrates by bacteria and microorganisms present inside the human body (the so-called microbiota). Their importance is due to the fact that different SCFA profiles can be connected both to a different diet of the subject, and to a different model of the intestinal microbiota but also to the health of the host.
The analytical procedure consisted of all the steps necessary to pretreat the sample so that it could be subsequently analyzed by means of thermo-desorption coupled with gas chromatography and tandem mass spectrometry (TD-GC-MS / MS). Particular attention and consideration have been given to the optimization of the parameters of a solid phase extraction of the analytes from the biological matrix in order to preconcentrate them and subject them to derivatization reactions. For derivatization a selective derivatizer for SCFAs was needed, which guaranteed a quantitative reaction but also an adequate thermal stability for an analysis in TD-GC-MS / MS.
The choice was to use pentafluorobenzyl bromide as derivatizing agent.
In the context of the analysis, all the instrumental parameters associated with thermal-desorption, chromatographic separation and detection were also optimized.