A miniaturized emission spectrometer coupled with headspace injection for rapid and sensitive determination of...

Nitrite (NO₂^-) is widely present in foods and their production processes, and yet excessive intake can pose a serious threat to human health. Thus, it is crucial to develop sensitive methods for NO₂^- analysis, preferably offering low cost and on-site analytical capabilities. In this study, a miniaturized emission spectrometer was developed to determine NO₂^- by detecting the characteristic molecular emission spectrometry (MES) of N-containing NO at 237.0 nm, which was generated from the reaction between NO₂^- and potassium iodide. To improve sensitivity, an automated headspace injection sampling strategy was designed and coupled to the MES detection unit. The gaseous analyte of NO was produced and accumulated in the headspace bottle and then rapidly transported to the subsequent miniature array microplasma excitation source for emission spectrometric determination. Thus, the sensitivity of NO₂^- analysis was considerably improved, while the complex pretreatment steps and analytical time were reduced. Under optimal experimental conditions, the limit of detection was 3 μg L^-1, and the relative standard deviation was 3.8 % (for 0.1 mg L^-1, n = 9). The proposed method successfully detected NO₂^- in certified reference materials and real food samples, demonstrating its accuracy and reliability. Furthermore, the constructed device offers the additional advantages of compact size and structure, making it highly promising for rapid, on-site analysis of nitrite in food field.