Development of an Analytical Method for Determination of Nitrate in Leafy Vegetables Using Ion Chromatography

The presence of nitrate in food in general may indicate a threat to human health. Nitrate can be converted to nitrite, a toxic species, in saliva and in the gastrointestinal tract. This work describes a precise and sensitive method using ion chromatography to determine nitrate (NO-3) in hardwood vegetables. In the proposed method the extraction of the nitrate of the vegetal matrix was carried out in an aqueous medium at a temperature of 70°C. The limit of detection (LOD) for the determined ion was 0.06 μg·L-1. The accuracy of the method was evaluated as the relative standard deviation (DPR) of the analytical signal area and the retention time, with values of 0.63% and 0.41%, respectively, for a solution of NO-3 5.0 mg·L-1. The detector presented linearity between 0.22 and 10 mg·L-1 with a correlation coefficient of 0.9999. The accuracy of the procedure was evaluated by addition/recovery test using real samples in which values greater than 95% were obtained. The validation of the proposed method was also performed by comparing the NO-3 concentrations obtained using the selective ion electrode method (EIS). The paired Student t test and the F test showed that both methods provide equivalent results concerning accuracy and precision.