Analysis of Some Heavy Metal Contents in Selected Vegetables and Fruits from States in Nigeria

Abstract

The consumption of fruits and vegetables is on the increase as these produce have nutritive values associated to the presence of essential metals that helps boost humans’ immune system, thus, avoiding health problems. However, there is also the presence of some non-essential metals in fruits and vegetables that are detrimental to humans. This study was carried out in order to determine the concentrations of some potentially toxic heavy metals namely; Lead (Pb), Cadmium (Cd), Nickel (Ni) and Zinc (Zn) in some leafy vegetables namely; cucumber (Cucumis sativus), watermelon (Cucurbita lanatus), tomatoe (Solantum lycopersium) and pepper (Capsicum annuum), brought from Kano state as well as those cultivated in Edo state. 25 samples consisting of 4 different vegetables were each purchased from two major markets known to be a major depot for vegetables in Benin City as well as those produced in Benin City, Edo State, Nigeria. Edible portions of the samples were used for analysis while bruised or rotten samples were removed. Samples for analysis were dried using the oven-dry method at 105°C for 24 hours to obtain the moisture content and then grounded. About 1.0g of the samples were each weighed and digested in a mixture of 10mls Nitric – Perchloric acid in a 250 ml Kjeldahl flask under a fume hood. The content was mixed and heated gently at 120 - 200°C for about 45 minutes on a hot plate. Heavy metals were present in all the vegetables analyse at various levels. Cadmium (Cd) concentration ranges between 0.02 – 0.47 mgkg-1, Lead (Pb) was within the range of 0.03 – 11.12 mgkg-1, Zinc (Zn) concentration ranges between 0.15 – 73.69 mgkg-1, and Nickel (Ni) concentration ranges between 0.07 – 35.54 mgkg-1 respectively in all the vegetables from the two states. Cd and Pb were observed to be higher than that of the Maximum Permissible Limit (MPL) stipulated by the World Health Organization (WHO).