The Investigation of Fluorescence Spectra and Fluorescence Quantum Yield of Enrofloxacin

Abstract

In this paper, the fluorescence spectra of Enrofloxacin (ENR) in different pH conditions was studied in order to determine its structural changes due to protonation with pH changes. The ENR two-step dissociation constant is calculated and the fluorescence quantum yield under acidic conditions is measured. In the strong acidic conditions, ENR exists of H 3 L 2+ form of which maximum emission wavelength is at 450 nm. At the condition of pH 2.45 to 4.23, ENR exists of H 2 L + form with strong and steady fluorescence. The maximum emission wavelength is still 450 nm. At the condition of pH more than 4.23, the maximum emission wavelengths are gradually blue shifted to 445 nm and the fluorescence intensity decrease with the increase of pH which shows that H 2 L + loses one proton with the increase of pH and exists in the form of bipolar ion HL. When the pH is more than 12.28, the fluorescence intensity are weakened to nearly disappear with the increase of pH value, indicating that HL gradually loses the proton with the conversion to the anion of Lwhich is weaker fluorescence. In the buffer solution of pH 3.00, with quinine sulfate as reference, the fluorescence quantum yield of ENR at excitation wavelength of 274 nm is 0.125.

Role of Metal–Chloride Anions in Photoluminescence Regulations for Hybrid Metal Halides

“…When the pH value is larger than 4.23, Enrofloxacin exists in the form of L (bipolar), and the maximum emission wavelength gradually shifted to 445 nm with the decreased fluorescence intensity. When the pH value is more than 12.28, Enrofloxacin exists in the form of L – (anion), the maximum emission wavelength is still at 445 nm, but the fluorescence intensity decreased and nearly disappeared with the increase of the pH value . One can conclude that the divalent cation species only exist in extremely acidic conditions.…”

“…We attribute these blue emissions to the singlet state fluorescence emission of EnrofloH 2 2+ cations, because the Enrofloxacin in solution also shows the similar blue emissions. 20,33 As mentioned above, Enrofloxacin exists in the form of LH 2 2+ (divalent cation) in the strong acidic conditions, in which the maximum emission wavelength is located at 450 nm. When Enrofloxacin exists in the form of LH + (monovalent cation) under the pH condition of 2.45− 4.23, the maximum emission wavelength is still at 450 nm.…”

“…When the pH value is more than 12.28, Enrofloxacin exists in the form of L − (anion), the maximum emission wavelength is still at 445 nm, but the fluorescence intensity decreased and nearly disappeared with the increase of the pH value. 33 One can conclude that the divalent cation species only exist in extremely acidic conditions. Therefore, we analyze the optical properties of Enrofloxacin in HCl solution with the concentration of 11−12 mol/L (ENR-HCl); the fluorescence spectra of ENR-HCl are shown in Figure S3.…”

Fabrication of PVC Enrofloxacin-Selective Electrodes for Estimating Enrofloxacin in Pure Form and as Preparation Formula

“…1 shows the chemical structure of enrofloxacin. The literature has revealed several logical strategies for quantitative assessment of enrofloxacin by spectrophotometry [7][8][9] , HPLC 10,11 , fluorescence 12,13 , and electrochemical technique 14 . The aim of this study is to foster an original particle-specific terminal method to determine enrofloxacin ionselective electrodes in drug measurement.…”