A novel agar gel-based colorimetric test tube for visual detection of nitrite in pickled mustards

Abstract

In the present work, a new strategy for visual detection of nitrite in pickled mustards based on the principle of diazotization coupling reaction was proposed. Under acidic conditions, nitrite could induce the formation of the purplish red compound by reacting with sulfanilamide and N-ethylenediamine (NETH). The Euclidean distance (ED) presented a good linear relationship with nitrite concentration from 0.1 to 15 μg/mL (R2 = 0.976). Additionally, the agar gel-based colorimetric test tube was further developed by combining the agar and reaction regents. The linear range of detection of colorimetric test tube for nitrite were 0.1–3 μL/mL and 5–20 μL/mL, respectively, demonstrating good quantitative analysis ability. The agar gel-based colorimetric test tube presented great selectivity and anti-interfering properties towards nitrite and was successfully applied for the detection of nitrite in different pickled mustards, demonstrating great practical application prospects. The proposed agar gel-based colorimetric test tube exhibits the advantages of simple preparation, convenient to carry, easy operation, fast reaction and data visualization, is beneficial for the real-time and on-site detection of nitrite, and is helpful for the food safety supervision of pickled mustards.