Development of on-line spectrofluorimetric methodology for selenium monitoring in foods and biological fluids using Chrome azurol S quenching.

A novel, simple and accurate on-line green methodology for Se(IV) monitoring by molecular fluorescence has been developed. Because the analyte does not exhibit fluorescence, the organic dye Chrome azurol S (CAS) has been chosen to allow detection. The effect of metal-quenching on CAS excitation and emission conditions (λex=300nm; λem=407nm) was used as criterion for analyte quantification in presence of sodium cholate bile salt (NaC). The quenching mechanism was explored, and it can be classified as a collisional type with a Stern-Volmer constant value of 3.0×107 molL-1 . To improve the sampling rate, minimize the reagent consumption and generated wastes, an on-line configuration was designed. Experimental variables that affect the fluorimetric sensitivity were optimized using uni-variation assays. Under optimal experimental conditions, the limit of detection was 0.27µgL-1 with a lineal range for Se(IV) concentration from 0.84 to 6.00µgL-1 . The developed methodology is low cost and fast sampling, allowing Se(IV) quantification in the presence of other common ions. Bulbous vegetables and biological samples were successfully analyzed with an average recovery close to 100%.