This study attempts at uniting the analysis of four different classes of contaminants for both liquid and solid tea samples. A total of 32 compounds, classified as pesticides, mycotoxins, process-induced toxicants or packaging contaminants, were carefully chosen for their diversity of structures and physicochemical properties. The proposed method combines a sample treatment strategy coming from metabolomics with liquid chromatography analysis using a silica bonded C18-pentafluorophenyl column coupled to high resolution mass spectrometry. For tea brew, dilute and shoot method provides good quantification (70-120% recoveries and <20% RSD) for more than 80% of compounds. For tea leaves, strong matrix effects are observed, thus, matrix-matched calibration is required to reach good performances, i.e. 63% of compounds quantified and 81% detected at 10µg/kg. Finally, method performances were evaluated against existing regulations, and it appears that 69% of contaminants are quantified and 91% detected at levels lower than their respective European regulation limits.

Educational resources that cover essential knowledge related to chemistry safety rules are openly accessible on the CHIMACTIV website (http://chimactiv.agroparistech.fr/). Organized into two online tracks, the content covers personal and collective protections, first aid, as well as the handling of hazardous chemicals. Being interactive and abundantly illustrated by photos and videos, these resources may be used by teachers to encourage (or even oblige) their students to self-train before lab sessions. Our user experience shows that students improve their chemical safety knowledge and culture upon consulting these resources: they arrive in the lab more confident and are more attentive to safety rules (especially concerning safety glasses and gloves), with a deeper knowledge of chemical hazards and of waste management options. Thanks to their digital responsiveness, these open resources may also be accessible during the lab sessions, enabling the students to get the information "just-in-time". In addition, decision trees for liquid and solid waste management are available, helping the students to gain reflexivity as well as to acquire good laboratory practice during lab sessions. In this way, the supervisors of the practical work sessions waste much less time taking back students who do not follow the safety rules properly.