Guaiazulene in health care products: Determination by GC–MS and HPLC-DAD and photostability test

A liquid chromatographic method with UV detection (HPLC-DAD) and a gas chromatographic method coupled with mass spectrometry (GC–MS) have been developed for the determination of guaiazulene (GA) in complex matrices such as creams and toothpastes. A solid phase extraction (SPE) sample pre-treatment on a polymeric sorbent (Strata-X polymer) was applied before the HPLC analyses, which were performed on a XTerra™ C8 stationary phase, using a mobile phase consisting of acetonitrile–water 50:50 (v/v). For GC–MS analyses, solid–liquid extraction (creams) and SPE (toothpastes) were applied. The proposed methods, based on techniques with different selectivity, were validated and both proved to be suitable to obtain an unambiguous identification and reliable determination of GA in commercial health care products (creams and toothpastes), giving concordant results. Moreover, the described methods can offer a useful analytical support for photostability studies of GA, a photolabile natural compound, in creams.