Quantification of caffeine in dietary supplements and energy drinks by solid-surface fluorescence using a pre-concentration step on multi-walled carbon nanotubes and Rhodamine B

TALÍO, MARÍA CAROLINA; ACOSTA, GIMENA; ALESSO, MAGDALENA; LUCONI, MARTA OLGA; FERNANDEZ, LILIANA

Food Additives & Contaminants: Part A

Taylor & Francis

Lugar: London; Año: 2014 vol. 31 p. 1367 - 1374

1944-0049

A new method for the determination of caffeine, a non-fluorescent analyte, based on the enhancement of the fluorescence ofRhodamine B dye on a membrane filter modified with multi-walled carbon nanotubes is proposed. The method comprisespre-concentration of caffeine on a solid support by chemofiltration in buffered solution onto multi-walled carbon nanotubespreviously oxidised and dispersed in cationic surfactant admicelles. The effect of experimental parameters, including thenature of the buffer and pH, the nature of the solid support, filtration flow rate, dye and carbon nanotube concentration, andthe nature of the surfactant and concentration were investigated by means univariation assays. Under optimum experimentalconditions, the pre-concentration system gave detection and quantification limits of 0.3 and 1.1 μg l−1, respectively. A widelinear range was achieved varying from concentrations of 1.1 to 9.7 × 103 μg l−1 (r2 = 0.999). Satisfactory recovery valueswere obtained using the method of standard addition, confirming the feasibility of this method for caffeine determination inenergising dietary supplements and energy drinks.