Characterizing the Interaction between Antibiotics and Humic Acid by Fluorescence Quenching Method

Abstract

The method of Three-Dimensional Excitation Emission Matrix Fluorescence Spectrophotometer was used to identify the interaction mechanism between humic acid (HA) and antibiotics. The effects of antibiotic concentration, temperature, and pH on the bonding strength between HA and antibiotics were investigated. The results showed that with the increase of antibiotics concentration, the quenching effect on HA was enhanced. The quenching of HA by both oxytetracycline (OTC) and sulfadiazine (SD) is a single static quenching of the complexes, and the interaction forces are mainly a hydrogen bond and the van der Waals force. The quenching constant KsvOTC > KsvSD and the binding constant KbOTC > KbSD, indicates that HA has a more obvious quenching effect on OTC. The Kb of HA by OTC ranged from 3.223 × 103 to 12.784 × 103 L·mol−1 in the range of 298 K to 313 K, while the Kb of HA by SD ranged from 2.051 × 103 to 5.533 × 103 L·mol−1. With the increase of temperature, the quenching constant Ksv and binding constant Kb of both OTC and SD by HA gradually decrease, and the low temperature is beneficial to the interaction. The composite of OTC and HA is more stable than SD. Under neutral alkaline conditions, both OTC and SD had the strongest quenching effect on HA, and the resulting complex was the most stable. However, the Ksv and Kb of HA by OTC were greater than SD in the pH range of the experiment and the pH effect on quenching of HA by OTC (Ksv) was greater than that of SD.

Biosynthesis of Cu nanoparticles supported on carbon nanotubes and its catalytic performance under different test conditions

“…At alkaline pH, the van der Waals force and electrostatic interactions between many of the OH‐generated nanocomposites on the surface of the catalyst and 4‐NP were weakened significantly. This may have also caused further reduction in the removal rate of 4‐NP . Finally, there was a remarkable decline in both the adsorption performance and the catalytic activity of the nanocomposites.…”

“…This may have also caused further reduction in the removal rate of 4-NP. 57 Finally, there was a remarkable decline in both the adsorption performance and the catalytic activity of the nanocomposites. In either a strong alkali or a strong acid environment, the catalytic activity of the nanocomposites with 4-NP was not improved.…”

Zinc Binding to Fulvic acids: Assessing the Impact of pH, Metal Concentrations and Chemical Properties of Fulvic Acids on the Mechanism and Stability of Formed Soluble Complexes

“…According to Hudson and Reynolds [48] and Patel-Sorrentino et al [49], such changes are a consequence of structural transitions in the molecule consisting in assuming a coiled, spherocolloidal shape at low pH and a gradual expansion to linear form at increased pH. Long-tailed configuration of humic substances at neutral and alkaline pHs, resulting from repulsion between negatively charged function groups [27], makes fluorophores more exposed and reveals their high fluorescence intensity [50]. Protonation of functional groups at acidic pH leads to polymerization and aggregation of molecules, as well as to a stronger hydrogen bonding effect and, in consequence, to a sharp decrease in fluorescence intensity.…”

“…The increase in the stability of FA-Zn(II) compounds with a simultaneous increase in the pH may result from higher spatial availability of metal to structures such as carboxyl and phenol groups responsible for the formation of strong complex bonds. In their studies on interactions between humic acids and antibiotics, Wang et al [50] reported an increase of stability constant with the pH up to pH 8. These results revealed that complexation may be hampered at acidic pH due to interactions of the hydrophobic surface of humic acids (protonated, aggregated structures) with hydrophilic quencher, as well as that the binding was stronger at neutral and alkaline pH due to interactions of the hydrophilic surfaces of humic acids with hydrophilic quencher.…”

Adsorption Characteristics of Oxytetracycline by Different Fractions of the Organic Matter from Humus Soil: Insight from Internal Structure and Composition

“…The adsorption behavior of antibiotics is further affected by clay minerals, metal oxides, and organic matter in soil [13][14][15]. Although there is little organic matter in soil, it can strongly affect the fate of antibiotics in soil [15,16]. Soil is negatively charged owing to organic matter surface contained polar functional groups, for instance, hydroxyl, carbonyl, and carboxyl.…”