Determination of nitrate in leafy vegetables by flow injection analysis with potentiometric detection

A rapid, simple and inexpensive flow injection potentiometric method for the determination of nitrate in leafy vegetables is described. Six commonly consumed fresh leafy vegetables (mint, lettuce, savoy cabbage, stinging nettle, parsley and cress) were obtained from bazaar in Samsun. An all-solid-state miniaturized nitrate-selective electrode was used as a detector in a low-dead-volume flow through cell. Nitrate was determined in the linear range from 0.1 to 100 mmol/L with detection limit of 0.066 mmol/L. The calibration slope is 52.96 ± 1.02 mV/decade in the linear range. The relative standard deviation (RSD) of the electrode response of 100, 10 and 1 mmol/L NO 3 - was 0.46, 0.49 and 0.98%, respectively. The flow injection analysis (FIA) throughput was 90 samples/h. The FIA results were compared with those obtained by spectrophotometric method. The results of the study show that nitrate contents in fresh leafy vegetables ranged from 97 to 1861 mg/kg.