Solid phase extraction cartridges 6cc

Solid phase extraction and ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) were utilized to detect the presence of 16 antibiotics from 7 classes in 11 influent and 11 effluent samples supernatants using a modified protocol ^{33 (link)}. Fifty ml of influent or effluent sample were centrifuged at 10,000 rpm for 10 minutes; supernatants were concentrated using solid phase extraction cartridges (6cc, 200 mg, Waters, Milford, MA). Samples were analyzed on a 4000 QTRAP LC/MS/MS instrument (AB Sciex). The data was normalized based on the internal standard (isotopically labeled caffeine, 13C3, Cambridge Isotope Laboratories) to account for experimental variation and antibiotic extraction/ionization efficiency. A mixture of the antibiotic standards was also processed along with the samples as positive controls to test for recovery. Standards for amoxicillin, cefotaxime, cefoxitin, chloramphenicol, ciprofloxacin, clindamycin, erythromycin, penicillin G, sulfamethoxazole, tetracycline, and trimethoprim were purchased from Sigma-Aldrich (St. Louis, MO). Standards for azithromycin, aztreonam, cefepime, doxycycline, and tigecycline were purchased from AK Scientific (Union City, CA). All analyses were performed at the Proteomics and Mass Spectrometry Facility at the Donald Danforth Plant Science Center (St. Louis, MO).