Solid-Phase Fluorimetric Determination of Tetracyclines in Medicinal Preparations on Cellulose Paper and in Thin-Layer Silica Gel Using a Smartphone

The possibility of determining the active substances of antibacterial drugs of the tetracycline series (tetracycline, doxycycline, oxytetracycline, demeclocycline, metacycline, and chlortetracycline) using solid-phase fluorescence digital colorimetry is considered. The intrinsic fluorescence of tetracyclines and tetracycline-sensitized fluorescence of europium on cellulose paper and a thin layer of silica gel was studied. Yellow-green (tetracyclines) and pink (europium) fluorescence were observed upon irradiation with UV light (365 nm) of spots of tetracycline solutions applied to the matrix. The fluorescence intensity on the matrix surface was measured using a smartphone. Values of colorimetric parameters in the RGB system were used as the analytical signals (Ar). The limits of detection and quantitation were 1 – 5 and 3 – 17 μg/mL, respectively, for all analytes. The ranges of the determined concentrations were 3 – 500 μg/mL. The technique was tested for medicinal products. The relative standard deviation of the analytical results was ≤0.06.