title: Improved detection of multiple environmental antibiotics through an optimized sample extraction strategy in liquid chromatography-mass spectrometry analysis.
abstract: A solid-phase extraction/liquid chromatography/electrospray ionization/multi-stage mass spectrometry (SPE-LC-ESI-MS/MS) method was optimized in this study for sensitive and simultaneous detection of multiple antibiotics in urban surface waters and soils. Among the seven classes of tested antibiotics, extraction efficiencies of macrolides, lincosamide, chloramphenicol, and polyether antibiotics were significantly improved under optimized sample extraction pH. Instead of only using acidic extraction in many existing studies, the results indicated that antibiotics with low pK a values (<7) were extracted more efficiently under acidic conditions and antibiotics with high pK a values (>7) were extracted more efficiently under neutral conditions. The effects of pH were more obvious on polar compounds than those on non-polar compounds. Optimization of extraction pH resulted in significantly improved sample recovery and better detection limits. Compared with reported values in the literature, the average reduction of minimal detection limits obtained in this study was 87.6% in surface waters (0.06-2.28 ng/L) and 67.1% in soils (0.01-18.16 ng/g dry wt). This method was subsequently applied to detect antibiotics in environmental samples in a heavily populated urban city, and macrolides, sulfonamides, and lincomycin were frequently detected. Antibiotics with highest detected concentrations were sulfamethazine (82.5 ng/L) in surface waters and erythromycin (6.6 ng/g dry wt) in soils. The optimized sample extraction strategy can be used to improve the detection of a variety of antibiotics in environmental surface waters and soils.
authors.affiliation: Department of Civil and Environmental Engineering, National University of Singapore, Singapore, 117411, Singapore.
authors.forename: Xinzhu
authors.initials: X
authors.lastname: Yi
authors.affiliation: Department of Food Science and Agricultural Chemistry, McGill University, Ste-Anne-de-Bellevue, Quebec, H9X 3V9, Canada.
authors.forename: Stéphane
authors.initials: S
authors.lastname: Bayen
authors.affiliation: Department of Civil and Environmental Engineering, National University of Singapore, Singapore, 117411, Singapore.
authors.forename: Barry C
authors.initials: BC
authors.lastname: Kelly
authors.affiliation: Department of Civil Engineering, University of Nebraska-Lincoln, Lincoln, NE, 68588-6105, USA.
authors.forename: Xu
authors.initials: X
authors.lastname: Li
authors.affiliation: School of Civil Engineering and Division of Environmental and Ecological Engineering, Purdue University, 550 Stadium Mall Drive, West Lafayette, IN, 47907, USA. zhizhou@purdue.edu.
authors.forename: Zhi
authors.initials: Z
authors.lastname: Zhou
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry* / Q000302:isolation & purification; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D004917:Erythromycin / Q000032:analysis / Q000302:isolation & purification; D012989:Soil Pollutants / Q000032:analysis / Q000302:isolation & purification*; D052616:Solid Phase Extraction / Q000379:methods*; D013449:Sulfonamides / Q000032:analysis / Q000302:isolation & purification; D053719:Tandem Mass Spectrometry / Q000379:methods*; D014874:Water Pollutants, Chemical / Q000737:chemistry* / Q000302:isolation & purification
chemical_list: D000900:Anti-Bacterial Agents; D012989:Soil Pollutants; D013449:Sulfonamides; D014874:Water Pollutants, Chemical; D004917:Erythromycin
keywords: Antibiotics; Extraction efficiency; Liquid chromatography-mass spectrometry; Surface waters; Urban soils; pK a