Quinine is included in the positive list of the European Union as a food flavouring additive and as it is a potentially toxic drug, it is used with a limit of 100 mg/l in different non-alcoholic beverages. Two rapid and sensitive methods were utilized. The first method is based on measuring the synchronous fluorescence spectra of quinine at Δλ = 100 nm in 0.05 M H2SO4. The second method, high-performance liquid chromatography (HPLC) separation was performed in less than 10 min; UV detection was performed at 250 and 275 nm and fluorescence detection at 375 nm after excitation at 325 nm; standard solutions of quinine were prepared in Milli-Q water. Both methods are suitable for the analysis of tonic waters. Constant-wavelength synchronous spectrofluorimetry method is considered as a good method, which is selective and more sensitive, quick and inexpensive for determining quinine content.
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