The Applications Of Metal-organic Coordination Polymers In Detection Of Tetracycline Antibiotics And Adsorption Of Sodium Fluorescein

Metal-organic coordination polymers (MOCPs) attract considerable attentions and show potential applications in gas purification and separation, catalysis, sensing and drug delivery/release owing to the very large surface area, tunable pore sizes, high thermal stability, as well as tempting magnetic, electrical, optical, and catalytic properties. However, there are few reports about their applications in pharmaceutical analysis and dye adsorption. Here, we investigated the interaction of Zn[1,4-bis(imidazol-1-ylmethyl)benzene](Zn(bix)) and tetracycline antibiotics (TCs) as well as the interaction of chromium-benzenedicarboxylates (MIL-101) and fluorescein sodium, and then Zn(bix) and MIL-101were applied for visual detection of tetracycline antibiotics and adsorption of sodium fluorescein from water, respectively.1. A rapid, simple and sensitive method for visual detection of TCs was developed based on the turned on fluorescence induced by a metal-organic coordination polymer of Zn(bix). Tetracycline antibiotics, such as tetracycline hydrochloride (TC), doxycycline hyclate (DC), chlortetracycline hydrochloride (CTC) and oxytetracyline hydrochloride (OTC), showed very weak fluorescence in Tris-HCl buffer of pH8.68～9.40. However, the fluorescence intensities of these TCs were greatly enhanced in the presence of Zn(bix) and were found to be proportional to the concentrations of TCs. Accordingly, TCs could be quantitatively determined with the detection limits of12.0,6.0,19.0and19.0nM for TC, DC, CTC and OTC, respectively. Furthermore, this fluorimetric method was successfully applied to the determination of DC contents in doxycycline hyclate tablets from three factories.2. A metal-organic framework of chromium-benzenedicarboxylates (MIL-101) was employed as an effective adsorbent for removal of fluorescein sodium from aqueous solution. The adsorption kinetic and isotherms were investigated, it was found that the adsorption process fitted the pseudo-second-order kinetic model and the adsorption isotherms followed the Langmuir model. The zeta potential changes of MIL-101after adsorption of fluorescein sodium showed the electrostatic interactions between MIL-101and fluorescein sodium, and the comparison of MIL-101and a zeolitic imidazolate framework of ZIF-8in the adsorption amount of fluorescein sodium confirmed the importance of the large pore of adsorbent for adsorption. The adsorption thermodynamics were investigated and some parameters including free energy, enthalpy and entropy changes were calculated, the results indicated that the adsorption of fluorescein sodium on MIL-101was a spontaneous and endothermic process. The adsorption capacity of MIL-101for fluorescein sodium at different temperatures was determined as well. In addition, the regeneration of MIL-101showed that it was a reusable adsorbent to remove fluorescein sodium from aqueous solution.