quantification of rhodamine b and fluorescein in microliter samples using multivariate fluorescence data from paper surface

Abstract: a simple, facile, and cost-effective method is described for quantification of two commonly used fluorophores, rhodamine b (rhb), and fluorescein (flu), using solid surface fluorescence data from the filter paper surface. spectrofluorometers are common for measurement of fluorescence from liquid samples however, this work is a simple method for recording fluorescence data from solid rhb and flu samples applying any common spectrofluoremeter assisted with a simple device. the hand-made device is a holder cuvette for measurement of the three-dimensional excitation emission matrix (3d-eem) of fluorescent data from a paper strip. applied wavelength ranges were 300-600 nm for excitation and 400-700 nm for emission. for rhb-paper strip the fluorescence intensity remarkably was increased compared to rhb in solution, and flu-paper showed acceptable fluorescence intensity although it is not emissive in the solid-state. considered concentration ranges of flu and rhb were 10.0 to 100.0 μm and 2.0 to 25.0 μm, respectively. moreover, in the solid mixture (rhb-flu-paper strip) the forster resonance fluorescence transfer (fret) was observed from flu to rhb, the same as the observed behavior in the liquid form. finally, analytes were successfully quantified using powerful multivariate methods such as partial least squares (pls) and parallel factor analysis (parafac) and coefficient of determination (r2) >0.90 was obtain. main advantages of the presented solid surface fluorescence technique is the microliter scale of required samples, and lower fluorescence self-absorption compared to liquid samples.