Novel method for determination of zinc traces in beverages and water samples by solid surface fluorescence using a conventional quartz cuvette.

A new method for zinc pre-concentration/separation and determination by molecular fluorescence is proposed. The metal was complexed with o-phenanthroline and eosin at pH 7.5 in Tris; a piece of filter paper was used as a solid support and solid fluorescent emission measured using a conventional quartz cuvette.

Sequential determination of lead and cobalt in tap water and foods samples by fluorescence.

In this work, a new procedure was developed for the separation and preconcentration of lead(II) and cobalt(II) in several water and foods samples. Complexes of metal ions with 8-hydroxyquinolein (8-HQ) were formed in aqueous solution. The proposed methodology is based on the preconcentration/separation of Pb(II) by solid-phase extraction using paper filter, followed by spectrofluorimetric determination of both metals, on the solid support and the filtered aqueous solution, respectively.

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.

A new method for the determination of caffeine, a non-fluorescent analyte, based on the enhancement of the fluorescence of Rhodamine B dye on a membrane filter modified with multi-walled carbon nanotubes is proposed. The method comprises pre-concentration of caffeine on a solid support by chemofiltration in buffered solution onto multi-walled carbon nanotubes previously oxidised and dispersed in cationic surfactant admicelles. The effect of experimental parameters, including the nature of the buffer and pH, the nature of the solid support, filtration flow rate, dye and carbon nanotube concentration, and the nature of the surfactant and concentration were investigated by means univariation assays.

Caffeine monitoring in biological fluids by solid surface fluorescence using membranes modified with nanotubes.

Background: In this work, a new methodology based upon enhancement of rhodamine B fluorescent signal is proposed for the quantification of caffeine traces.

Methods: Membrane filters treated with multiple wall carbon nanotubes were employed as solid support for determination 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.