Dispersive solid phase extraction/fluorescence analysis of riboflavin using sepiolite as sorbent

The use of a natural clay, sepiolite (Sep), and graphene (G)/Sep mixtures as sorbents for the solid phase extraction in dispersive mode (dSPE) with fluorescence detection of a biologically interesting molecule, riboflavin, is reported. The retention of riboflavin by Sep is quantitative with different volumes of the sample and 10?50?mg of the clay. The desorption process has been performed using aqueous solutions of surfactants of different nature: anionic sodium dodecylsulphate (SDS), cationic hexadecyltrimethylammonium chloride (CTAC) and non-ionic polyoxyethylene-23-lauryl eter (Brij L23). The non-ionic surfactant provides the highest riboflavin recoveries; upon optimization of the process, that takes less than half an hour, an extraction yield of 93% was attained using 40?mM Brij L23. The developed method has been applied to the analysis of beer, soya drink and infant milk samples with excellent accuracy (recoveries of 100%) and very good precision, avoiding the interferences of the matrix components that hinder the direct fluorescence analysis of riboflavin.