Nitrate and nitrite in commercial samples of conventional, organic and hydroponic leafy vegetables

The aim of this research was to investigate along four weeks the nitrate and nitrite levels in commercial samples of leafy vegetables (lettuce, watercress, spinach, and rocket) of different growing systems (hydroponic, conventional and organic) using a capillary electrophoresis method. In all samples, nitrite content was below the limit of detection, while nitrate was quantified. The nitrate concentrations in the leafy vegetables ranged from 239.26 to 7873.00 mg kg(-1) in fresh weight, with more expressive values found for lettuce, watercress and rocket in the hydroponic system, while for spinach the highest values were found in the conventional system. However, the lettuce can be highlighted as the vegetable with the lowest content of nitrate and the rocket the vegetable with the highest content of this compound. Despite the great variability, the nitrate levels found for most samples were in accordance with international requirements.