A Solid-phase Fluorescent Quenching Method for the Determination of Trace Amounts of Nitrite in Foods with Neutral Red
RONG LI1, JIMMY C. YU2, ZI-TAO JIANG1,2*, REN-HUA ZHOU1 AND HO-YAN LIU2
1.Department of Food Science and Engineering, Tianjin University of Commerce, Tianjin 300400, P. R. China
2.Department of Chemistry and Environmental Science Programme, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong
(Received: October 1, 2002; Accepted: February 27, 2003)
ABSTRACT
A simple and sensitive solid-phase fluorescent quenching method for the determination of trace amounts of nitrite in food samples has been developed. The method is based on the reaction between nitrite and neutral red, which is used as an emission reagent, to form a non-fluorescent compound in 0.1 mol/L hydrochloric acid. The fluorescent intensity was measured in 5-mm quartz cells with excitation and emission wavelengths of 548 and 609 nm, respectively. The degree of fluorescent quenching showed good linearity at concentrations of nitrite between the ranges of 40-200 mg/L. The detection limit is 8.1 mg/L and the RSD is 1.7%. The general coexisting ions do not interfere with the reaction of neutral red with nitrite. The proposed method was applied to the determination of trace amounts of nitrite in food samples with satisfactory results. In addition, the mechanism involved in the reaction was discussed.
Key words: nitrite, neutral red, solid-phase spectrophotofluorimetry, fluorescence quenching, b-cyclodextrin epichlorohydrin polymer (b-CDEP)