Nitrate contents in some vegetable leaves in Sokoto Metropolis, Nigeria

Popular Nigerian vegetables namely, cabbage, spinach, bitter leaf, water leaf, ewedu, roselle and lettuce obtained from Sokoto metropolis, Nigeria were analysed for nitrate contents by ultra-violet (UV)-spectrophotometric method. The fresh leaves of the samples were chopped and ground using mortar and pestle for the analysis. Absorbance of each sample was obtained in three replicate and the calibration graph of standards nitrate were used in determining the concentration of each sample. Cabbage, spinach, ugwu and lettuce contain the lowest amount of nitrate in this study (0.109 ± 0.035 µgml-1, 1.530 ± 0.130 µgml-1, 1.730 ± 0.328 µgml-1 and 2.185 ± 0.157 µgml-1) in comparison with the nitrate contents of samples like roselle, ewedu, water leaf and bitter leaf which contain the highest amount (2.938 ± 0.060 µgml-1, 3.682 ± 0.140 µgml-1, 3.924 ± 0.160 µgml-1 and 4.351 ± 0.190 µgml-1). These values fall within those recommended for nutritional purpose.   Key words: Nitrate contents, vegetables, Sokoto, absorbance.