Study On Passive Sampling Method Of Macrolide Antibiotics In Water

As the most concerned group of pharmaceuticals,antibiotics have been used extensively in human and veterinary medicine,as well as in aquaculture.Antibiotics can be more or less metabolized by humans and animals.After administration,antibiotics and their metabolites are excreted into the effluent and reach the sewage treatment plants(STPs).But antibiotics are only partially eliminated in sewage treatment plants.They may still exist in the effluents and end up in the environment,resulting in a steady-state concentration in aquatic systems,which has been described as "pseudo-persistent".Antibiotics have been found ubiquitously in river water of China,usually below ?g/L level.Active sampling using pumps or grab sampling has been commonly used for environmental monitoring of antibiotics.However,pre-treatment and cleanup of large volumes of water samples collected by active sampling are very complex and time-consuming.Another inherent problem of grab sampling is that the sample only represents the levels at a specific place and time.Passive samplers are relatively new emerging tools for sampling micropollutants in waters.They can lower limits of quantification and detection(LOQs and LODs).They are relatively simple to operate,and generally small and light.They are also energy-saving.In addition,they can provide time-weighted average concentrations,thus providing a more accurate concentration levels of pollutants.In this study,five macrolide antibiotics were selected as the target analytes,using the newly-developed passive sampler to study the passive sampling method.A high performance liquid chromatography-tandem mass spectrometry(LC-MS/MS)method was improved for the determination of five macrolides(Roxithromycin,Clarithromycin,Azithromycin,Spiramycin and Tylosin)in natural water samples.The macrolides were extracted from water samples using Oasis HLB cartridges.The recoveries of the five macrolides ranged from 64.8%to 90.83%.The instrumental limits of detection and quantification were 0.012-0.085?g/L and 0.041-0.285?g/L,respectively.Only Tylosin was not found in the studied river water and the effluent of sewage treatment plants using the established method,while the other four macrolides were detected at ng/L level.In this study,a cylindrical passive sampling device(4cm diameter × 4cm height)was made of stainless steel mesh.XAD18 resin was selected as the adsorbent and filled in the passive sampler.This work provided an understanding of the adsorption performance of five macrolides onto XAD18.The results showed that XAD18 had a high adsorption capacity of the target analytes,and even at a low temperature,the adsorption capacity was still greater than 100?g/g.The sampling rates(Rs)of the newly developed passive sampler for the five macrolides were obtained through calibration experiments under laboratory conditions.The Rs for the five macrolides varied from 0.024 L/d to 0.0456L/d,and the Rs for Roxithromycin was the highest.The uptake of the five macrolides in passive sampler with time followed a liner pattern,and the linear correlation coefficients were all above 0.93.The Rs could be increased by 1-2 times when the flow rate was doubled.For Roxithromycin,Clarithromycin and Azithromycin,the sampling rates were significantly higher at pH 5 than at higher pH treatment.But for Tylosin and Spiramycin,the sampling rates reached the maximum at pH 8.Except for Spiramycin,when the salinity was increased from 0%to 1.2%,the Rs were increased 1.46-3.45 times.There was a positive correlation between Rs and LogKow in fresh water,which was not observed in salty water(with a salinity of 3.5%).Continuous observations within 6 and 7 days were performed in order to promote the application of self-made passive sampler in natural water,compared with the results based on conventional grab samples.The results showed that higher concentrations were obtained for Roxithromycin and Clarithromycin using passive sampler compared to the values from the grab samples in sampling site A.While in sampling site B,all the antibiotics were detected in passive sampler.And the concentrations determined by spot sampling were partially comparable to the concentrations obtained by the passive sampler,except that Tylosin was not detected in spot sampling.In summary,the passive sampling following laboratory calibration experiment can accurately detect the concentrations of the macrolide antibiotics in natural water and can be widely used.