title: Hyphenation of coupled-column liquid chromatography and thermospray tandem mass spectrometry for the rapid determination of beta 2-agonist residues in bovine urine using direct large-volume sample injection. Set-up of single-residue methods for clenbuterol and salbutamol.
abstract: In a previous work, coupled-column LC (LC/LC) with direct large-volume sample injection for the analysis of beta 2-agonists in bovine urine was investigated, in view of its combination with thermospray (TSP) tandem mass spectrometric (MS/MS) detection. In this work, the potential of both conventional LC and LC/LC coupled to TSP-MS/MS for the rapid determination of beta 2-agonists in bovine urine was evaluated. It was first established that, in order to avoid disturbances in TSP-MS/MS detection due to changes in pressure and flow rate of the mobile phase, LC/LC is preferable to conventional LC. Then, selecting clenbuterol and salbutamol as model compounds for the class of beta 2-agonists, two single-residue LC/LC/TSP-MS/MS methods were developed, permitting the determination of the analytes in bovine urine samples with a limit of quantification of at least 0.1 ng, ml-1, with a sample throughput of 4 h-1. The methods were validated by analysing both spiked urine samples and samples containing clenbuterol or salbutamol residues. Mean recoveries from urine samples spiked with clenbuterol at levels of 5 and 0.22 ng ml-1 were 107% (n = 9, RSD = 7.4%) and 102% (n = 6, RSD = 14%), respectively. A bovine urine sample containing 1.28 ng ml-1 clenbuterol residue (previously quantified by GC/MS) was re-analysed by LC/LC/TSP-MS/MS on four different days (n = 3, each day) and yielded a mean concentration of 1.31 ng ml-1, with a reproducibility of 8.4%. Bovine urine samples spiked with salbutamol at levels of 10.8 and 0.55 ng ml-1 yielded mean recoveries of 101% (n = 3, RSD = 1%) and 89% (n = 3, RSD = 13%), respectively. In bovine urine samples containing salbutamol residues, the concentrations of unconjugated salbutamol were found to be in the range 8-57 ng ml-1.
authors.affiliation: National Institute of Public Health and Environmental Protection (RIVM), Bilthoven, The Netherlands.
authors.forename: E A
authors.initials: EA
authors.lastname: Hogendoorn
authors.forename: P
authors.initials: P
authors.lastname: van Zoonen
authors.forename: A
authors.initials: A
authors.lastname: Polettini
authors.forename: M
authors.initials: M
authors.lastname: Montagna
mesh_terms: D058666:Adrenergic beta-2 Receptor Agonists; D000318:Adrenergic beta-Agonists / Q000652:urine*; D000420:Albuterol / Q000652:urine*; D000818:Animals; D002417:Cattle; D002853:Chromatography, Liquid; D002976:Clenbuterol / Q000652:urine*; D004350:Drug Residues / Q000032:analysis*; D007202:Indicators and Reagents; D013058:Mass Spectrometry; D013056:Spectrophotometry, Ultraviolet
chemical_list: D058666:Adrenergic beta-2 Receptor Agonists; D000318:Adrenergic beta-Agonists; D007202:Indicators and Reagents; D000420:Albuterol; D002976:Clenbuterol