Native fluorescence flow-through optosensor for the fast determination of diphenhydramine in pharmaceuticals

A single, rapid flow-through optosensor spectrofluorometric system is proposed for the determination of diphenhydramine in different pharmaceutical preparations. This sensor was developed in conjunction with a monochannel flow-injection analysis system with fluorometric solid-phase transduction. Diphenhydramine was directly injected into a carrier stream of ethanol/water, 50% (v:v), and transitorily retained on a sorption gel Sephadex G-15 placed in the detection area into the cell. The determination was carried out without any derivatization reaction by directly measuring the intrinsic fluorescence of the analyte and using the peak height as an analytical signal. The chemical and instrumental variables were optimized, and the influence of some foreign substances that can be found in typical pharmaceutical samples containing diphenhydramine was also investigated. Diphenhydramine could be determined in the concentration ranges of 0.5 - 8 microg ml(-1) and 0.1 - 1.2 microg ml(-1) with detection limits of 0.088 and 0.019 microg ml(-1) at sampling rates of 30 and 19 h(-1) for 200 and 800 microl of the sample volume, respectively.