title: Characterisation of the abiotic degradation pathways of oxytetracyclines in soil interstitial water using LC-MS-MS.
abstract: The fate of oxytetracyclines (OTCs) in soil interstitial water was investigated and the structure of a number of degradation products elucidated in a time-related experiment. A previously developed separation method for LC-MS-MS able to base separate and quantify OTC and three of its epimers and degradation products was applied. Compounds detected were 4-epi-oxytetracycline (EOTC) (t(R)=3.0 min), OTC (t(R)=4.4 min), alpha-apo-oxytetracycline (alpha-apo-OTC) (t(R)=11.4 min) and beta-apo-oxytetracycline (beta-apo-OTC) (t(R)=18.4 min). Furthermore, we tentatively identified 4-epi-N-desmethyl-oxytetracycline (E-N-DM-OTC) (t(R)=3.0 min), N-desmethyl-oxytetracycline (N-DM-OTC) (t(R)=3.5), N-didesmethyl-oxytetracycline (N-DDM-OTC), 4-epi-N-didesmethyl-oxytetracycline (E-N-DDM-OTC) (t(R)=3.7 and 4.7 min) and 2-acetyl-2-decarboxamido-oxytetracycline (t(R)=8.7) in all samples. Most compounds were only present in trace concentrations (less than 2%) relative to the parent OTC. EOTC was on the other hand formed up to a ratio of 0.6 relative to parent OTC concentration. Only EOTC, E-N-DM-OTC, N-DM-OTC, N-DDM-OTC and E-N-DDM-OTC were formed during the time-related experiment. All other compounds were probably only present as impurities in the spiked OTC formulation as they declined in concentration from the start of the experiment. Half-lives (T(1/2), days) of the OTCs in soil interstitial water were in the order of 2 days (EOTC) to 270 days (beta-apo-OTC).
authors.affiliation: Department of Analytical and Pharmaceutical Chemistry, Section of Environmental Chemistry, The Royal Danish School of Pharmacy, Universitetsparken 2, DK-2100 Copenhagen Ø, Denmark. bhs@dfh.dk
authors.forename: Bent
authors.initials: B
authors.lastname: Halling-Sørensen
authors.forename: Anne
authors.initials: A
authors.lastname: Lykkeberg
authors.forename: Flemming
authors.initials: F
authors.lastname: Ingerslev
authors.forename: Paul
authors.initials: P
authors.lastname: Blackwell
authors.forename: Jette
authors.initials: J
authors.lastname: Tjørnelund
mesh_terms: D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D013058:Mass Spectrometry / Q000379:methods*; D010118:Oxytetracycline / Q000737:chemistry*; D012015:Reference Standards; D012989:Soil Pollutants; D014874:Water Pollutants, Chemical
chemical_list: D012989:Soil Pollutants; D014874:Water Pollutants, Chemical; D010118:Oxytetracycline