title: Confirmatory analysis of sulfonamide antibacterials in bovine liver and kidney: extraction with hot water and liquid chromatography coupled to a single- or triple-quadrupole mass spectrometer.
abstract: A simple, specific, and rapid confirmatory method for determining 12 sulfonamide (SAs) antibacterials in bovine liver and kidney is presented. This method is based on the matrix solid-phase dispersion technique with hot water as extractant followed by liquid chromatography/mass spectrometry (LC/MS) with an electrospray ion source. The method was tailored for use with both single-quadrupole MS (I) and triple-quadrupole MS (II) instruments. After acidification and filtration of the aqueous extract, a 250-microL aliquot was injected into instrument I while only 25 microL was analyzed by instrument II. With instrument I MS data acquisition was performed in the selected ion monitoring (SIM) mode, selecting at least three ions for each target compound. With instrument II the selected reaction monitoring (SRM) mode with three fragmentation reactions for each compound was chosen. With the exception of sulfaquinoxaline (SQX), recovery of the analytes at the 50 ppb level in both liver and kidney was 72-96% with relative standard deviations (RSDs) ranging between 3 and 11%. The very poor recovery of SQX was due to its rapid enzymatic oxidation when in contact with the two tissues. With instrument I, limits of quantification (LOQs, S/N = 10) were 5-14 ppb of SAs. Even lower LOQs (1-8 ppb) were estimated by using instrument II, even though the extract volume analyzed was ten times lower than that with instrument I. With both matrices and using instrument I, severe ion signal suppression was experienced for the early-eluted SAs when trying to fractionate analytes by using a short chromatographic run time. This effect was traced to polar endogenous co-extractives eluted in the first part of the chromatographic run that interfered with gas-phase ion formation for SAs. Adopting more selective chromatographic conditions minimized this effect.
authors.affiliation: Dipartimento di Chimica, Università "La Sapienza", Piazza Aldo Moro 5, 00185 Roma, Italy.
authors.forename: Sara
authors.initials: S
authors.lastname: Bogialli
authors.forename: Roberta
authors.initials: R
authors.lastname: Curini
authors.forename: Antonio
authors.initials: A
authors.lastname: Di Corcia
authors.forename: Manuela
authors.initials: M
authors.lastname: Nazzari
authors.forename: Manuel
authors.initials: M
authors.lastname: Sergi
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000493:pharmacokinetics*; D002417:Cattle; D002853:Chromatography, Liquid; D004350:Drug Residues / Q000493:pharmacokinetics; D006358:Hot Temperature; D007668:Kidney / Q000378:metabolism*; D008099:Liver / Q000378:metabolism*; D013058:Mass Spectrometry / Q000379:methods*; D015394:Molecular Structure; D013449:Sulfonamides / Q000737:chemistry / Q000493:pharmacokinetics*; D014020:Tissue Extracts; D014867:Water / Q000737:chemistry*
chemical_list: D000900:Anti-Bacterial Agents; D013449:Sulfonamides; D014020:Tissue Extracts; D014867:Water