A.S. Osipov, L.A. Truhacheva

In stop mode, the flow through the fluorescent detector manufactured by fluorescence scanning of samples of sorbic and benzoic acids in the alleged mobile phases for chromatography. As a result of scanning is determined that the registration of benzoic acid, the optimum excitation wavelength 231 nm and emission of 322 nm. For sorbic acid values of wavelengths 272 nm and 335 nm, respectively. Increase in the proportion of methanol in an acidic mobile phase causes a significant decrease in the fluorescence of benzoic acid (44 %), whereas an increase in methanol content in the mobile phase has no effect on the absorption (λ 225 nm)-benzoic acid. With increasing pH of the mobile phase, a sharp drop in the fluorescence of benzoic acid. In the application of the mobile phase acetonitrile - 50 mM K2HPO4 (pH 7.5) (3:7) at 91 % decreases the fluorescence of benzoic acid. In contrast, the decrease in the absorption of benzoic acid with increasing pH of the mobile phase is much less pronounced (12 %). When chromatography of benzoic and sorbic acid on a column of Zorbax SB C18 150 x 4.6 mm (5 m) using a mobile phase of acetonitrile - 0.085 % phosphoric acid in water (3:7) defined the limits of detection of benzoic and sorbic acids for fluorescence and UV detection. The limit of detection (at signal / noise ratio 5:1) for benzoic acid was 0.25 ng for fluorescence detection, and 0.10 ng for UV detection. This option is for the sorbic acid was 2.36 ng for fluorescence detection, and 0.037 ng for UV detection. Fluorescence detection is not acceptable for the analysis of sorbic acid due to low sensitivity compared with UV detection for chromatography. In the case of benzoic acid, the lower sensitivity of fluorescence detector does not matter because of the relatively high concentration of preservatives in pharmaceuticals (0,5-1mg / ml). Moreover, the fluorescent detection of benzoic acid may have an advantage because of the selectivity of determination, which is especially important for analysis of multicomponent drugs of natural origin.