ABSTRACT
A simple, rapid, and convenient method for the determination of neomycin based on the ion association method was proposed. In Britton-Robinson buffer solution, neomycin could react with Congo red to form an ionic association, which in turn reacted with dodecyl trimethyl ammonium bromide to form a ternary ionic association. The three were combined in a 1 : 1 : 1 ratio, which significantly enhanced the resonant Rayleigh scattering intensity at 468 nm. The obtained resonant Rayleigh scattering sensor showed a linear relationship with neomycin in the range of 0.07â¼1 µg·mL-1. The limit of detection was 0.02 µg·mL-1, and the limit of quantification was 0.037 µg·mL-1. The experimental conditions were optimized. The method was verified based on the ICH rule. The established method could be applied to the analysis of the acceptable recovery rate of neomycin in powdered veterinary drugs.
ABSTRACT
Two simple, sensitive, and low-cost fluorescence spectroscopy methods for neomycin (NEO) detection were developed. Both methods were based on the interaction between NEO and Congo red (CR) in acidic buffer medium to form an ion-association complex. The quenching effect of the formed ion-association complex on the fluorescence of CR at 421 nm is a basic principle of fluorescence analysis, whilst the resonance Rayleigh scattering (RRS) method was used to enhance the resonance Rayleigh scattering spectrum at 384 nm by adding NEO. Experimental conditions such as pH, temperature, reaction time, CR concentration, and the ionic strength of the two methods were investigated and optimized. In addition, the effect of common coexisting substances on the method was tested and the results showed good selectivity. The composition of ion-association complexes, the reaction mechanism, and reasons for the enhanced intensity of RRS are discussed. Under optimum conditions, the responses of the fluorescence spectrophotometry and RRS methods showed good linearity with NEO concentrations in the range 0.2-3.0 µg ml-1 and 0.1-3.0 µg ml-1 , respectively. The detection limits of fluorescence spectrophotometry and RRS spectroscopy techniques were 0.02 µg ml-1 and 0.01 µg ml-1 , respectively. Finally, the two methods were applied to the analysis of wastewater and the results were satisfactory.
Subject(s)
Congo Red , Neomycin , Neomycin/analysis , Congo Red/chemistry , Spectrometry, Fluorescence/methods , Wastewater/analysis , Scattering, RadiationABSTRACT
Understanding the hydrolysis behavior and pathway of norfloxacin (NOR) in the hyporheic zone (HZ) is important for predicting its environmental persistence. Therefore, the effects of different environmental factors on NOR hydrolysis were investigated, and the hydrolysis pathway of NOR in the HZ was determined by DFT calculations and UPLC/TOF-MS. The hydrolysis process of NOR was consistent with the first-order kinetic. The experiment of environmental factors showed that DO was an important factor to affect NOR hydrolysis, and its hydrolysis rate was positively correlated with DO concentration. The superoxide radical (·O2-) was the main active species for NOR hydrolysis. The hydrolysis rates of NOR under neutral and alkaline conditions were higher than that under acidic conditions in both aerobic and anoxic environments. The ions of Ca2+, Mg2+, HCO3-, CO32-, and NO3- in simulated water samples inhibited the hydrolysis of NOR, while Cl- promoted its hydrolysis. In addition, the electronegativity of NOR was determined by DFT calculations, and it was speculated that the active sites of NOR hydrolysis were mainly located in the piperazine ring and quinolone ring. The main hydrolysis pathway of NOR in aerobic environment was piperazine ring cracking and quinolone ring decomposition, and that in anoxic environment was piperazine ring cracking. The results are of great significance to evaluate the environmental fate of NOR in the HZ and provide a theoretical basis for further understanding the degradation and governance of fluoroquinolones in water environment.
