Proceedings Volume 2010 (format .pdf) - SimpBTH

Reversed-phase liquid chromatography (RPLC) of flavonoids over a C18derivatised silica stationary phase is most commonly used [32]For the separation of flavonoids, the chromatographic conditions of HPLCmethod include the using of a C 18 column with reversed-phase; a UV-Vis detectorand a binary system solvent containing acidified water and a polar organic solvent(methanol, acetonitrile).Mass spectrometry is one of the physical-chemical methods applied todetermine the structure of organic compounds. The MS characteristic is based onusing different physical principles, both for sample ionization and for ionsseparation, ions that are generated according to m/z ratio (m – mass, z – charge).Among the methods of sample pretreatment for GC–MS analysis, headspaceSPME offers certain advantages. Firstly, it is a sample non-destructive method.Secondly, it concentrates volatile compounds allowing their detection even at tracelevel and so requires only small amount of sample. Thirdly, non-volatilecompounds such as fats, waxes and polysaccharides, are not extracted by such amethod, thus avoiding the fastidious sample pre-treatment required for classicalGC–MS analysis.Terpenes are a group of lipophilic aliphatic compounds originating fromthe secondary metabolism of plants [33].Terpenes are volatile compounds synthesized and stored in plant vegetative organs[34]. These compounds can be transferred from the forages eaten by the animalsinto dairy products and used as a marker to distinguish milk and cheese originatedfrom animals in grazing systems from those produced from indoor-fed animals orto trace the geographical origin or production site of the milk [Error! Bookmarknot defined.].Mono- and sesquiterpenes are highly volatile compounds, diterpenesexhibit low volatility, triterpenes very low volatility and polysaccharides are notvolatile.Mono- and sesquiterpenes can be easily trapped by headspace SPME, whichimplies the terpenes volatilization from the sample in a closed space, followed bythe analysis of the constituents in this gaseous phase.The GC method is the most efficient chromatographic techniques for theseparation of terpenes. The capillary columns with dimethyl polysiloxane (nepolarphase) and Carbowax 20M (polar phase) are used. Sometimes, when theselectivity of one column is not sufficient, especially when the mixture is verycomplex, there have been used coupled techniques, such as GC-GC and HPLC-GC,which give a better resolution. Both of them allow the using of techniques withdifferent abilities of separation, combining chiral and achiral or polar and nepolarcolumns.294