Many herbal food supplements (containing plants) are available on the Belgian market to the general public. The legal framework for herbal food supplements is provided by the Royal Decree (KB) dated 24.01.2017, in which a list is published of a large number of plant species that are allowed to be used as a food supplement, but for part of them particular analytical requirements have been imposed. The same list also applies in France and Italy. However, in many cases appropriate analytical methods are not available yet, and should urgently be developed and validated. It can be requested that given compounds or classes of compounds should completely be absent, or that only a maximum level can be tolerated. The aim of this project is to develop and validate analytical methods to detect (and to establish detection limits) or to quantify concerned products. It should be considered that from a legal point of view a requirement such as “does not contain detectable amounts of …” requires the use of the most appropriate and sensitive technology available today, which in general is LC-MS (liquid chromatography – mass spectrometry) or GC-MS (gas chromatography – mass spectrometry). The following plant species have been selected in this project in order to establish a limit of detecion: Scuttelaria lateriflora L. (furano-neoclerodanes), Styphnolobium japonicum L. (Sophora japonica L.) (alkaloids), Lepidium meyenii Walp. (alkaloids); and with regard to methods to quantify a particular compound or class of compounds: usnic acid in various lichens; glucosinolates such as progoitrin and goitrin in members of the Brassicaceae and Tropaeolaceae.