After extraction, the various group

After extraction, the various groups of phenols are commonly analyzed by reversed-phase HPLC using a C18 column and UV–vis diode array detector (DAD). Mass and tandem mass spectrometry play an important role, especially for identification purposes. Although HPLC is the primary technique used for the analysis of polyphenols, several studies refer to the analysis of flavonoid aglycones by gas chromatography using silylation to convert the analytes into volatiles. Examples of this type of analysis can be found using on-column injection, analysis of polyphenols in apple pomace and apple juice. Flavonoid aglycones have also been explored in model systems and citrus fruits by means of a prior oximation step to obtain a better response, particularly for anthocyanins and apple. In addition, a few studies have attempted to analyze flavonoid glycosides as trimethylsilyl (TMS) derivatives using high temperature chromatography. However, these efforts were only qualitative.