Study On Novel Methods For The Determination Of Trace Nitrate And Fluoroquinolones Residue And Its Application

Chapter1： The significance and headways trend of the health laboratorytechnologies for norfloxacin, lomefloxacin and nitrate were introduced respectively.The basic principles and the basis of quantitative determination for three analysismethods of the health laboratory technologies for them were also introduced briefly inthis topic.Chapter2：A fluorescent method for the synchronous determination of norfloxacinand lomefloxacin was developed. In order to avoid the interference from the twoisomers, the synchronous fluorescence and differentiate-synchronous fluorescencespectra of the two kinds of fluoroquinolones were studied, and the zero-crossingmethod for reading spectral intensities was adopted. At pH4.0（HAc–NaAc bufferwater solution） and Δλ=160nm, the synchronous fluorescence wavelengths were at283.8nm and275.0nm for norfloxacin and lomefloxacin, respectively. In the optimalexperimental conditions, there was a linear relationship between the differentiate-synchronou fluorescence intensity and the concentration of norfloxacin andlomefloxacin in the range of1.68×10^-8to5.64×10^-6mol·L^-1and1.89×10^-8to6.19×10^-6mol·L^-1, respectively. The limits of detection （LOD） were found to be5.03×10^-9mol·L^-1for NFLX,7.58×10^-9mol·L^-1for LFLX. The proposed method is reliable,selective and sensitive, and has been used successfully in the determination of tracesof NFLX and LFLX in milk samples. The mechanism of the co-luminescence reactionand the reasons for fluorescence enhancement has been discussed.Chapter3： The fluorescence characteristic of NFLX and NFLX-Y3+wereinvestigated in the present paper. The experimental results indicated that Y3+ioncould greatly increase the fluorescence intensity of NFLX in the system. Based on this,a simple and sensitive fluorescence method for determining the NFLX was developed. Under the optimal conditions, There was a good linear relationship between thefluorescence intensity of the system and the concentration of NFLX in the range of5.10×10^-95.64×10^-6mol·L^-1. The correlation coefficient was0.9993and thedetection limit （S/N=3） was1.52×10^-9mol·L^-1. The presented method was used todetermine the NFLX in actual milk samples and oblatum samples with the satisfactoryresults. The recoveries were in the range of94.0%¹05.0%and RSD were in therange of2.0%⁴.5%. In addition, the luminescence mechanism of the NFLX-Y3+system was also discussed.Chapter4： The properties of resonance fluorescence of Rhodamine G （RhG）were studied. RhG itself has a strong resonance fluorescence signal that the resonancefluorescence peak is tine and symmetry in hydrochloric acid medium, without theinterferece of foreign substances. Based on the catalytic effect of nitrite on theoxidation reactiov of RhG by potassium bromate, a catalytic resonance fluorescencemethod was proposed for the determination of trace nitrite. The affecting factors ofintensity of resonance fluorescence and the optimum conditions of the reactionsystems were investigated. The maximum resonance fluorescence peak of RhG waslocated at540nm. The decrease intensity of resonance fluorescence was inproportional to the concentration of NO2-. The detection limit and the linear range forNO2-were1.65μg·L^-1and4.20⁵6.00μg·L^-1, respectively. The NO2-inenvironmental water samples were analyzed by the proposed method with satisfactoryresults. The recovery of environmental water was98.84%¹04.33%and the RSDwas less than5.0%. This method is sensitive, exact, simple and easy to do.