Solid-surface fluorescent properties of estrogens: Green analytical applications

For the first time, the fluorescent signals produced by 17β-estradiol (E2), estradiol valerate (E2V) and 17α-ethinylestradiol (EE2) were investigated after being retained in selected solid surfaces. Among different studied supports, both C18 and nylon membranes demonstrated to have been able to induce intense signals over their surface, after aqueous solutions of the analytes were retained via a solid-phase extraction procedure. Physicochemical variables which affect the quality of the fluorescence signals were optimized, and the results obtained in the studied solid supports were compared and discussed. While nylon successfully faced the trouble of spectrofluorimetrically quantifying estrogens in pharmaceuticals with unbalanced estrogen/progestagen ratios, C18 membranes showed very good qualities for second-order spectrofluorimeric measurements, allowing the determination of E2 (the most active estrogen) in potentially contaminated fish and chicken samples. The fluorescence excitation–emission matrices, directly measured on a C18 surface, were processed using appropriate chemometric algorithms in order to efficiently quantify E2 in the presence of natural matrix constituents. The present strategy avoids the elution step, considerably decreasing the use of organic solvents, the analysis time and the experimental errors. In addition, the instrumental involved is nonsophisticated and, therefore, the experiments could be carried out in routine laboratories.