Once a month, produce samples (the choice of which was
dependent on their respective availability i.e. the growing season)
were collected at the study site aseptically into a sterile Erlenmeyer
flask by randomly removing not less than 20 g of produce material
(leaves in the case of spinach and parsley and florets in the case of
cauliflower) from at least three different plants. To avoid soil based
contamination, material furthest away from the soil surface was
harvested. Samples were stored on ice before 10 g of produce material
was analyzed within 2 h.