High-performance ion chromatography assessment of inorganic and organic nitrogen fractions in potatoes

A new high-performance ion chromatography assay for organic and inorganic nitrogen analysis has been proposed and examined. In the devised protocol, inorganic sample constituents were measured after ultrasonically assisted water extraction. The amine and amide nitrogen content was assessed after modified Kjeldahl digestion and determined as NH₄⁺, and the total nitrogen content was quantified as NO₃⁻ after microwave-facilitated digestion. Finally, the nitro, azo, azoxy nitrogen was calculated by comparison of the total nitrogen content and all measured nitrogen species. The detection limits of the measured ions were 2.0, 0.82 and 0.17 mg L⁻¹ for nitrate, nitrite and ammonium, respectively. For samples of potatoes, the average shares of the nitrogen species found in the total nitrogen content were: 0.83% of nitrate nitrogen, <0.03% of nitrite nitrogen, 2.1% of ammonium nitrogen, 71% of nitro, azo, azoxy nitrogen, and 26% of amine, amide nitrogen. We expect the method to be applicable to different vegetable samples. The quality of the results obtained was verified by analyzing certified reference material and comparing to another analytical method.