Determination And Abiotic Attenuation Of Antibiotics In Water

Antibiotic is a kind of pharmaceuticals used to inhibit or abolish the growth of microorganisms. Antibiotic residues in water will do harm to in-situ microbial and human health. Accurate determination and studying on the attenuation of antibiotics in water are necessary. In this study,35 antibiotics belonged to sulfonamides, tetracyclines, quinolones, macrolides were selected, due to they were used widely and detected frequently. We optimizated the solid-phase extraction enrichment conditions, liquid chromatography conditions and mass spectrometric detection conditions. Then sulfachloropyridazine, chlortetracycline, diflorxacin, erythromycin, lincomycin were chosed as representatives to study their abio-attenuation behavior and to explore the effects of pH, humic acid and bivalent cation on attenuation of those selected antibiotics. The main results are as follows:1. An analytical method for the trace-level determination of 35 antibiotics in water was developed. Separation was performed on a C18 column. Use methanol/ acetonitrile (V/V,1/1) containing 0.1% formic acid as organic phase, and water with 0.1% formic acid as inorganic phase. Detection was finished in ten minutes. Selecting internal standards were depended on their rention time and characteristics. The linear of 35 antibiotics were good (R2>0.99). Intra-day precision (<2%) and inter-day precision (<10%) were all acceptable.2. Solid-phase extraction enrichment conditions were optimizated. At the level of 10 ng/L, recoveries of antibiotics standards in deionized water were between 53.79% and 103.84%, and recoveries of antibiotics standards in groundwater were between 56.79% and 93.64%. At the level of 40 ng/L, recoveries of antibiotics standards in deionized water were between 67.13% and 93.00%, and recoveries of antibiotics standards in groundwater were between 68.91% and 92.67%. And through adding antibiotics standards into ultrapure water, method detection limit was determined to be 0.29-4.03ng/L.3. In this study, abio-attenuation of antibiotics was fitted with pseudo first-order kinetics. In deionized water, the half-live of erythromycin was 11.5 days, and the half-live of chlortetracycline was 23.1 days, sulfachloropyridazine, diflorxacin, lincomycin did not attenuate. In groundwater, there was no obvious attenuation of erythromycin, but chlortetracycline attenuated quickly, and lincomycin attenuated at first, then stoped attenuating, sulfachloropyridazine and diflorxacin still did not attenuate. With the decreasing of pH, erythromycin attenuation became faster, but chlortetracycline became slower. There were complexes of lincomycin with Ca2+, so that the concentration became lower when Ca2+ existed. The presence of humic acid inhibited the attenuation behavior of erythromycin in the water, maked its half-life increased by 11.5 days to 34.7 days...