Comparison of three methods for determination of nitrate content in different vegetables

Abstract

Abstract Vegetables are the major source of dietary nitrate, with a wide range of nitrate content. The presence of nitrate in vegetables is often associated with harmful effects on human health, i.e. with toxic effects of methemoglobinemia and the possibility of causing an endogenous formation of carcinogenic N-nitroso compounds. Therefore, accurate measurement of nitrate in these products is of great importance. Various analytical techniques have been developed to determine nitrate in biological samples and vegetables. The purpose of this study is to compare the three methods BS EN 12014-2 (HPLC UV/Vis), ISO 6635, and Cd-column for nitrate measurement and to introduce an accurate, safe, and useful method for nitrate measurement in 11 important vegetables with a wide range of nitrate content. The results of this study showed strong agreement between the three methods. A strong and significant regression was observed between the HPLC run using ISO 6635 and the HPLC method using the Cd-column, with the slope of the regression curve close to 1 for most of the vegetable samples. Between HPLC and ISO 6635 methods, the fitted regression curve had slopes as high as 1.0946 and as low as 0.9195, respectively. While, the highest and lowest slopes of the fitted regression curve between HPLC and the Cd-column methods were 1.088 and 0.9217, respectively. The highest slope between the two methods ISO 6635 and Cd-column was equal to 1.0832 and the lowest was equal to 0.8421. The correlation coefficient of the regression equation was significant at a level of 99% (p ˂ 0.01) across all samples and correlations of linear regression. The results of this study showed that all three methods have high accuracy for nitrate measurement in vegetables. However, the type of sample and the accessibility of the facility plays a big role in the selection of an analytical method. The HPLC method is slower than the Spectrophotometry methods (ISO 6635 and Cd-column), despite having a higher initial investment cost. However, it has a lower risk of environmental pollution and health risk for the staff. Spectrophotometry methods have high speed, and the initial cost of equipment is lower, but they have more environmental risk and are labor-intensive than the HPLC method. Finally, despite the fact that the compared methods were very accurate at measuring nitrate in vegetables, the HPLC method is suggested because it is reliable, secure, and practical in vegetables due to the figure of merits mentioned.