• conductivity;
  • essential oil;
  • liquid chromatography;
  • quality parameter;
  • storage

Abstract:  Several analytical methods including high-performance liquid chromatography (HPLC) were applied on essential oils to establish a set of suitable quality parameters for monitoring changes during storage. For this purpose, 7 essential oils derived from various plant families were exposed to possible worst-case conditions for up to 3 mo at 38 °C under cool white light in the presence of atmospheric oxygen. After storage and immediate freezing at –80 °C to stop further alterations until analysis, individual physicochemical parameters were assessed and are discussed with regard to the precision of the respective method as well as suitability to monitor aging processes. To determine conductivity and pH values, a work-up of essential oils by water extraction was established. Conductivity, peroxide value as well as pH turned out to be suitable parameters to picture alterations. Additionally, HPLC fingerprints were monitored by diode array detection to track underlying chemical changes in essential oil composition.

Practical Application:  This study evaluates a set of analytical parameters to track changes during essential oil storage. On this basis, quality alterations can be monitored.