Background and Objectives: Seemingly no research has investigated so far to heavy metals determination in leafy vegetables widely consumed in Zanjan city using inductively coupled plasma (ICP) spectrometer. Therefore, the objective of present research was determine heavy metals contents (Zn, Pb, Cd, Co, Ni) in some selected leafy vegetables widely consumed in Zanjan city (Dill, leek, Coriander, Parsley and Cress) from three major cultivation areas (Rah Ahan, Dizaj Bala and Kushkan).

Materials and Methods: For more accurate results four pre-treatment methods (wet ashing with electrical furnace, acid leaching method and ultrasound-assisted acid leaching) and inductively coupled plasma (ICP) spectrometry were evaluated.

Results: Obtained results show that wet ashing is the effective method among other pre-treatment procedures. According to the obtained results about heavy metals measurement the level of these metals depended on the type of vegetable and different cultivation areas, so Rah Ahan region showed the highest contamination. Among evaluated heavy metals only the level of the Pb in all samples was higher than permissible levels recommended by standards (1.8-2.5 mg/Kg). The maximum and minimum concentrations of Pb were exhibited by Dill (9.28±1.95 mg/Kg), and leek (2.35±3.33 mg/Kg), respectively. The mean Ni, Cd and Co concentrations in vegetable samples varied from 0.44-3.93 mg/Kg, 0.1-0.2 mg/Kg and 0.5-1.08 mg/Kg, respectively, which were lower than the recommended safe limits. In the case of Zn, all of samples except Cress showed the concentration levels below the acceptable tolerance level (50 mg/Kg).

Conclusion: In general it can be concluded that pretreatment methods, both vegetable and cultivated area could be helpful in determining the amount of heavy metals pollution. Considering the importance of accurate determination of these metals, these factors should be considered.

Keywords: Heavy metals, Inductively coupled plasma, Leafy vegetables, Zanjan