Papers by carlos guerrero
Journal of Chromatography A, 2006
The potential of solid-phase extraction coupled on-line to liquid chromatography/electrospray tan... more The potential of solid-phase extraction coupled on-line to liquid chromatography/electrospray tandem mass spectrometry (SPE-LC-ESI-MS/MS) has been investigated in this paper for the efficient sensitive quantification and confirmation of 16 antibiotics in water. The list of targeted analytes included 10 quinolones (oxolinic acid (OXO), nalidixic acid (NAL), flumequine (FLU), marbofloxacine (MAR), ofloxacine (OFLO), enrofloxacine (ENR), pefloxacine (PEF), ciprofloxacine (CIP), pipemidic acid (PIPE), norfloxacine (NOR)) and 6 penicillins (penicillin G (PEN), oxacillin (OXA), dicloxacillin (DIC), piperacillin (PIP), cloxacillin (CLO) and ampicillin (AMP)) that were determined in ground and surface water. The procedure is based on the injection of 9.8 mL of sample into the SPE-LC-MS/MS system and the measurement of antibiotics by selected reaction monitoring mode, using a triple quadrupole analyser. The method has been validated at realistic low concentrations that might be present in environmental water, i.e. 10 and 100 ng L −1 , obtaining recoveries between 74% and 123% with relative standard deviation lower than 14%. Matrix effects were not relevant in most of cases, except for ampicillin in surface water, where notable signal suppression was observed. The limits of detection were as low as 0.4-4.3 ng L −1 . The method developed allows the rapid screening and quantification of all the analytes selected by acquiring one MS/MS transition (normally the most sensitive) for each compound. It was applied to a number of actual surface and groundwater samples with several compounds being detected, mainly quinolones, at low ng L −1 levels. Special attention was given to the confirmation of compounds detected in water due to the difficulties of obtaining confident confirmation at low ng L −1 . This matter has been of growing concern in the last few years as reflected by recent papers and correspondence. The acquisition of several MS/MS transitions for each compound detected in a second independent analysis allowed the unequivocal confirmation of identity, avoiding reporting false-positives. Finally, the potential of QTOF instruments to confirm positive samples has also been evaluated and compared with triple quadrupole analysers.
Journal of Chromatography A, 2009
The potential of ultra-high-pressure liquid chromatography (UHPLC) coupled to hybrid quadrupole t... more The potential of ultra-high-pressure liquid chromatography (UHPLC) coupled to hybrid quadrupole timeof-flight mass spectrometry (QTOF-MS) for the screening and confirmation of antibiotics in water samples is illustrated in this paper. UHPLC presents several advantages over conventional liquid chromatography as it generates narrow peaks (increasing peak height and improving sensitivity) and reduces chromatographic runs. Regarding QTOF-MS, its increased mass resolution, high sensitivity in full-spectrum acquisition mode and mass accuracy, in both MS and MS/MS modes, make this technique ideal for the detection and reliable confirmation of organic contaminants in environmental samples. After a solidphase extraction using Oasis HLB cartridges, UHPLC-QTOF-MS has been applied in this work to several types of water samples (surface water and influent and effluent wastewaters). Several antibiotics were found in the samples, such as ofloxacin, ciprofloxacin, clarythromycin or erythromycin, among others. Moreover, the full spectrum data provided by TOF-MS acquisition has enabled searching for many other pharmaceuticals that could be present in the samples in a "post-target" way. This approach has allowed the detection and confirmation of paracetamol, omeprazole and codeine, among others. UPLC-QTOF-MS has been shown as an attractive and efficient hyphenated technique for the rapid detection and confirmation of pharmaceuticals in water with very little sample handling.
Trends in Analytical Chemistry, 2007
Pharmaceuticals, identified as emerging contaminants, are used in large quantities in human and v... more Pharmaceuticals, identified as emerging contaminants, are used in large quantities in human and veterinary medicine for treatment of different diseases. Among pharmaceuticals, antibiotics in the aquatic environment are of great concern as prolonged exposure to low doses may ...
Artículo 153.-Las empresas tendrán derecho a ejercitar ante las Juntas de Conciliación y Arbitraj... more Artículo 153.-Las empresas tendrán derecho a ejercitar ante las Juntas de Conciliación y Arbitraje, las acciones que les correspondan en contra de los trabajadores por incumplimiento de las obligaciones que les impone este capítulo.
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Papers by carlos guerrero