Residue content of oxytetracycline applied on tomatoes grown in open field and greenhouse

A study was undertaken to evaluate the decline of the residues of oxytetracycline (OTC) in tomatoes grown in two different cultivation systems: open field (conventional cultivation) and greenhouse (protected cultivation). Tomato plants were subjected to a single chemical treatment, when fruits were at the breaker stage of maturation, by applying a commercial formulation at the doses recommended by the manufacturer. Fruit samples provided from open field and greenhouse were simultaneously and periodically taken until the end of the pre-harvest interval and submitted to analysis. A liquid–liquid extraction (LLE) and a silica-based C18 (octadecyl) solid-phase extraction (SPE) were used for sample preparation. High performance liquid chromatography (HPLC) with fluorescence detection was used to determine the OTC residues. Results showed that the recommended pre-harvest interval, indicated on the prospectuses of manufacturer, lowered the residue levels to acceptable legal limits and no statistical differences were observed between the cultivation systems in relation to the residue levels of OTC.