Rapid analysis of trace levels of antibiotic polyether ionophores in surface water by solid-phase extraction and liquid chromatography with ion trap tandem mass spectrometric detection.
ABSTRACT The occurrence of antibiotics in surface and ground water is an emerging area of interest due to the potential impacts of these compounds on the environment. This paper details a rapid, sensitive and reliable analytical method for the determination of monensin A and B, salinomycin and narasin A in surface water using solid-phase extraction (SPE) and liquid chromatography-ion trap tandem mass spectrometry (LC-MS-MS) with selected reaction monitoring (SRM). Several product ions as sodiated sodium salts for MS-MS detection have been identified and documented with their proposed fragmentation pathways. Statistical analysis for determination of the method detection limit (MDL), accuracy and precision of the method is described. The average recovery of ionophore antibiotics in pristine and wastewater-influenced water was 96.0+/-8.3% and 93.8+/-9.1%, respectively. No matrix effect was seen with the surface water. MDL was between 0.03 and 0.05 microg/L for these antibiotic compounds in the surface water. The accuracy and day-to-day variation of method fell within acceptable ranges. The method is applied to evaluate to the occurrence of these compounds in a small watershed in Northern Colorado. The method verified the presence of trace levels of these antibiotics in urban and agricultural land use dominated sections of the river.
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ABSTRACT: Hydrolytic and photolytic degradation were investigated for the ionophore antibiotics lasalocid, monensin, salinomycin, and narasin. The hydrolysis study was carried out by dissolving the ionophores in solutions of pH 4, 7, and 9, followed by incubation at three temperatures of 6, 22, and 28 °C for maximum 34 days. Using LC-MS/MS for chemical analysis, lasalocid was not found to hydrolyse in any of the tested environments. Monensin, salinomycin, and narasin were all stable in neutral or alkaline solution but hydrolysed in the solution with a pH of 4. Half-lives at 25 °C were calculated to be 13, 0.6, and 0.7 days for monensin, salinomycin, and narasin, respectively. Absorbance spectra from each compound indicated that only lasalocid is degraded by photolysis (half-life below 1 h) due to an absorbance maximum around 303 nm, and monensin, salinomycin, and narasin are resistant to direct photolysis because they absorb light of environmentally irrelevant wavelengths.Environmental Pollution 08/2013; 182C:177-183. · 3.73 Impact Factor
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ABSTRACT: A multi-residue pressurised liquid extraction (PLE) methodology has been established for the determination of the four ionophores: lasalocid, monensin, salinomycin and narasin in solid environmental matrices. The PLE methodology is combined with solid phase extraction as clean-up using liquid chromatography coupled to tandem mass spectrometry applying electrospray ionisation for detection. The samples were freeze-dried prior to extraction. The absolute recoveries for soil and sediment ranged from 71 to 123% (relative standard deviation (RSDs) below 16%) and in the range 94-133% (RSDs 9-35%) for poultry manure. The final method allowed for the detection of four ionophores down to a few hundred ngkg(-1) in natural solid matrices with limit of quantifications (LOQs) being 0.96, 0.87, 0.98, and 0.64μgkg(-1) in soil for lasalocid, monensin, salinomycin, and narasin, respectively. Corresponding LOQs in sediment were 1.28, 1.34, 1.39, and 0.78μgkg(-1) for the respective ionophores, while in manure the LOQs were 0.98, 1.01, 1.45, and 1.01μgkg(-1).Journal of chromatography. A 07/2013; · 4.19 Impact Factor
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ABSTRACT: The occurrence of pharmaceuticals in the aquatic environment has become a matter of concern in the last decade due to potential risks posed to non-target organisms and the potential for unintended human exposure via food chain. This concern has been driven by a high detection frequency for drugs in environmental samples; these substances are produced in large quantities and are used in both veterinary and human medicine, leading to deposition and potential effects in the environment. However, few studies have focused on the presence of pharmaceuticals in rural areas associated with farming activities in comparison to urban areas. The aim of this study is to investigate the occurrence of pharmaceutically active compounds in surface waters collected from urban and rural areas in northwestern Spain. A monitoring study was conducted with 312 river water samples analysed by high-performance liquid chromatography coupled to tandem mass spectrometry. Positive detection of pharmaceuticals was made for 51 % of the samples. Decoquinate, sulfamethazine, sulfamethoxypyridazine and trimethoprim were the drugs most frequently detected, being present in more than 10 % of the samples. The sampling sites located downstream of the discharge points for wastewater treatment plants yielded the highest number of positive samples, 13 % of the positive samples were detected in these sites and 38 % of the samples collected near the collection point of a drinking water treatment plant were positive.Environmental Science and Pollution Research 09/2013; · 2.62 Impact Factor