Determination of quinine in drugs and beverages by fluorimetric method

Abstract

A highly sensitive and simple fluorimetric method for the determination of quinine in pharmaceuticals and non-alcoholic beverages is proposed. The optimal conditions for quinine fluorimetric determination in drugs and beverages were found: solvent — 0.01 M sulfuric acid, excitation wavelength 353 nm, luminescence wavelength 452 nm, strobe parameters — signal delay 0.85 μs, signal duration 21.25 μs. To increase the sensitivity of the developed method, quinine luminescence was studied in sulfuric acid of various concentrations — from 0.005 to 1.000 M, and the quantum yield of quinine luminescence was calculated in all studied concentrations of sulfuric acid. It has been established that the highest luminescence intensity, the highest quinine quantum yield and the smallest background signal of the solvent was observed in 0.01 M H2SO4. The calibration curve exhibited the linear range from 0.10 to 1.00 mg/l. The limit of detection (LOD) was found to be 0.0029 mg/l for quinine in 0.01 M H2SO4. The suggested approach was successfully applied to determine the amount of quinine in tablets «Analgin-quinine» and in the non-alcoholic beverage «Schweppes Bitter Lemon». The proposed method can be used to control the quality of pharmaceuticals and food products.