CAFFEINE MONITORING IN BIOLOGICAL FLUIDS AND DIETARY SUPPLEMENTS BY SOLID SURFACE FLUORESCENCE USING RHODAMINE AND NANOTUBES MODIFIED MEMBRANES

Article

Summary *

In this work, a new methodology based upon enhancement of rhodamine B fluorescent signal is pro- posed for the quantification of caffeine traces. Methods: Membrane filters treated with multiple wall carbon nanotubes were employed as solid support for de- termination step by solid surface fluorescence. Results: Experimental variables that influence the preconcentration step and fluorimetric sensitivity have been optimized using uni-variation assays, presenting linearity from 1.1 to 9.7 × 103 μg/l, with a correlation coeffi- cient of 0.99. At optimal conditions, a limit of detection of 0.3 μg/l and a limit of quantification of 1.1 μg/l were obtained. The method showed good sensitivity and adequate selectivity and was satisfactorily applied to the de- termination of trace amounts of caffeine in urine, plasma and serum belonging to subjects with different sex, ages and habit of caffeine intake. Conclusions: Chemofiltration step eliminated the highly fluorescent matrix, thus enabling and allowing CF quan- tification, in the presence of other methylxanthines. The proposed methodology represents an innovative appli- cation of the solid surface fluorescence using membrane filters modified with MWCNTs. Information provided by the agent in SIGEVA