Comparison of detection methods of nitrite and application in laboratory, environmental, and food samples

Abstract

Measurement of nitrite is important for the monitoring and controlling of environmental pollution and food safety. Previous studies have described numerous methods for determining the concentration of nitrite. However, there are still some uncertainties for measuring nitrite in the presence of various interference, such as nitrate which is always coexisting with nitrite and some organic compounds which contain nitro-group. The objective of this study is to develop methods for quantifying the concentration of nitrite and investigate the influence of nitrate and nitro compounds in the quantification of nitrite. The method of high-performance liquid chromatography with fluorescence detection (HPLC-FLD), ultraviolet visible (conventional UV-VIS) absorption spectroscopy and liquid waveguide capillary cell-UV-VIS (LWCC-UV-VIS) are developed for the determination of nitrite. The measurement of nitrite bases upon the nitrite calibration curve to obtain the concentration of nitrite. For the nitrite calibration equations, they are built by a series of standard solutions with various concentrations of nitrite. It was found that the detection limit for HPLC-FLD, conventional UV-VIS and LWCC-UV-VIS method in nitrite measurement is recorded at 0.1, 0.3 and 0.02 μM respectively. For the interference analysis of the HPLC-FLD method, the presence of nitro compounds resulted in a significant influence on the quantification of nitrite while nitrate and nitro compounds had no effects on nitrite detection by conventional UV-VIS. Besides, the LWCC-UV-VIS method bases upon the same theory as conventional UV-VIS for nitrite detection, and it offers the advantages of high sensitivity and specificity for quantifying low levels of nitrite.