Determination Of Three Antibiotics Residues In Milk By Fluorescent Spectrophotometry

Antibiotics are widely used for animal clinic therapy,and are frequently added into feeds of the prevention or treatments of animal diseases.However,illegal administration will lead to residues in edible tissues,especially in the milk of galactophorous animals,and finally do latent harm to human health.Thus,it is necessary to develop a series of accurate sensitive and convenient assays.SpectrofluorimetryFluorescence spectura is a molecular emission spectrometry with high accuracy,good selectivity,and convenience,which has a great deveolpment in recent years.The fluorescent assays have been studied to determine three antibiotics residues in milk.A new determination method for tetracycline residue in milk is developed by fluorescent spectrophotometry in the thesis.Tetracycline can be hydrolyzed as strong fluorescent iso-tetracycline in 0.1mol/L NaOH solution.The fluorescence of the hydrolyzate can be intensified about 2-fold of itself by cetyltrimethyl ammonium bromide. The linear dynamic range is from 50μg/L to 2500μg/L,detection limit is 2.06μg/L,and the recoveries of spiked sample are between 84.56%and 90.06%.The method was successfully applied to the determination of tetracycline residue in milk.Penicillin has a broad spectrum of antibacterial activity and is widely used for prophylactic or therapeutic purpose in cow breeding.Penicillamine is one of the hydrolyzates of benzylpenicillin under acid condition and can be derivatized as hyperfluorescent 1-thio 2-aldyl iso-indole with o-phthaldehyde.A new fluorescent spectrophotometry assay based on the derivative reaction has been developed to determine benzylpenicillin residues.Under the conditions of hydrolyzation time 60 min,pH10.0, derivative reagent amount 40μL and reaction time 15min,the linear dynamic range is from 3.00μg/L to 5.0×10²Î¼g/L,the detection limit is 1.33μg/L,and the average recoveries of spiked sample is 89.10%.The requirement for residue benzylpenicillin in milk in national standards can be met with the assay.A new analytical method has been developed with fluorescamine derivation to determine neomycin residue in milk.Milk can be deproteinated with trichloroacetic acid. The influencing factors of derivation reaction such as pH of buffer,category of organic solvents and the concentration of trichloroacetic acid was optimized.Under the optimum conditions,organic solvent is acetone,pH is 7.2,derivative reagent amount 150μL,the linear dynamic range is from 0.1mg/L to 2.5mg/L,the detection limit is 5.2×10^-2mg/L, and the average recoveries of spiked sample is 90.88%.The requirement for residue neomycin in milk in national standards can be met with the assay.