title: Sorption and solubility of ofloxacin and norfloxacin in water-methanol cosolvent.
abstract: Prediction of the properties and behavior of antibiotics is important for their risk assessment and pollution control. Theoretical calculation was incorporated in our experimental study to investigate the sorption of ofloxacin (OFL) and norfloxacin (NOR) on carbon nanotubes and their solubilities in water, methanol, and their mixture. Sorption for OFL and NOR decreased as methanol volume fractions (fc) increased. But the log-linear cosolvency model could not be applied as a general model to describe the cosolvent effect on OFL and NOR sorption. We computed the bond lengths of possible hydrogen bonds between solute and solvent and the corresponding interaction energies using Density Functional Theory. The decreased OFL solubility with increased fc could be attributed to the generally stronger hydrogen bond between OFL and H2O than that between OFL and CH3OH. Solubility of NOR varied nonmonotonically with increasing fc, which may be understood from the stronger hydrogen bond of NOR-CH3OH than NOR-H2O at two important sites (-O18 and -O21). The interaction energies were also calculated for the solute surrounded by solvent molecules at all the possible hydrogen bond sites, but it did not match the solubility variations with fc for both chemicals. The difference between the simulated and real systems was discussed. Similar sorption but different solubility of NOR and OFL from water-methanol cosolvent suggested that sorbate-solvent interaction seems not control their sorption.
authors.affiliation: Faculty of Environmental Science & Engineering, Kunming University of Science & Technology, Kunming, Yunnan 650500, China.
authors.forename: Hongbo
authors.initials: H
authors.lastname: Peng
authors.affiliation: Faculty of Environmental Science & Engineering, Kunming University of Science & Technology, Kunming, Yunnan 650500, China.
authors.forename: Hao
authors.initials: H
authors.lastname: Li
authors.affiliation: Faculty of Environmental Science & Engineering, Kunming University of Science & Technology, Kunming, Yunnan 650500, China.
authors.forename: Chi
authors.initials: C
authors.lastname: Wang
authors.affiliation: Faculty of Environmental Science & Engineering, Kunming University of Science & Technology, Kunming, Yunnan 650500, China.
authors.forename: Di
authors.initials: D
authors.lastname: Zhang
authors.affiliation: Faculty of Environmental Science & Engineering, Kunming University of Science & Technology, Kunming, Yunnan 650500, China. Electronic address: panbocai@gmail.com.
authors.forename: Bo
authors.initials: B
authors.lastname: Pan
authors.affiliation: Stockbridge School of Agriculture, University of Massachusetts, Amherst, MA 01003, United States.
authors.forename: Baoshan
authors.initials: B
authors.lastname: Xing
mesh_terms: D000327:Adsorption; D000900:Anti-Bacterial Agents / Q000737:chemistry*; D006860:Hydrogen Bonding; D000432:Methanol / Q000737:chemistry*; D037742:Nanotubes, Carbon; D009643:Norfloxacin / Q000737:chemistry*; D015242:Ofloxacin / Q000737:chemistry*; D012995:Solubility; D012997:Solvents / Q000737:chemistry; D014867:Water / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D000900:Anti-Bacterial Agents; D037742:Nanotubes, Carbon; D012997:Solvents; D014874:Water Pollutants, Chemical; D014867:Water; D015242:Ofloxacin; D009643:Norfloxacin; D000432:Methanol
keywords: Antibiotics; Dissolution; Environmental fate; Hydrogen bond; Interaction energy