Rapid multi-residue analysis of antibiotics in muscle by liquid chromatography-tandem mass spectrometry.

A way of carrying out simple and rapid multi-residue analysis of antibiotics in porcine and bovine muscle by liquid chromatography-tandem mass spectrometry (LC-MS/MS) is described. The method has previously been published as a screening method, but the scope has now been extended to quantification and confirmation. Nineteen compounds from five different classes of antibiotics, i.e. tetracyclines, sulfonamides, quinolones, (-lactams and macrolides, are included in the method. The samples are extracted by a single extraction using 70% methanol, diluted with water and injected in the LC-MS/MS. The run time is 7min per injection. About 60 samples can be analysed in 24h. By using this method the need for a separate screening step prior to confirmation is eliminated and consequently the total time from sampling to a confirmed result will be considerably reduced. Validation was performed according to Commission Decision 2002/657/EC.

Rapid multi-residue method for the quantitative determination and confirmation of glucocorticosteroids in bovine milk using liquid chromatography-electrospray ionization-tandem mass spectrometry.

Dexamethasone, betamethasone and prednisolone are synthetic glucocorticosteroids authorized for therapeutic use in bovine animals within the European Union. Dexamethasone and betamethasone are used mainly for the treatment of metabolic and inflammatory diseases. Prednisolone is used to treat bovine mastitis. Maximum residue limits (MRLs) of 0.3 microg kg(-1) for both dexamethasone and betamethasone and 6.0 microg kg(-1) for prednisolone in bovine milk have been established. 6alpha-Methylprednisolone and flumethasone are not authorized for use in bovine animals and are completely banned in bovine milk. The proposed method is based on deprotenisation of milk using 20% (w/v) trichloroacetic acid. Samples are filtered using glass microfiber filters and subject to clean-up using OASIS HLB solid phase extraction. Separation was achieved on a Hypercarb 100 mm x 2.1 mm x 5 microm column. Mobile phase was: 90/10 acetonitrile/0.1% formic acid in water; flow rate was 600 microL min(-1). The method allowed the rapid identification and confirmation of the five glucocorticosteroids according to the criteria laid down in Commission Decision 2002/657/EC. Matrix calibration curves for all compounds were linear in the interval 0.0 MRL to 2.0 MRL with a correlation coefficient (r(2)) higher than 0.96. Relative recoveries ranged from 97% for betamethasone to 111% for prednisolone. Precision at the MRL ranged from 3.8% for prednisolone to 13.8% for betamethasone. Decision limits, CCalpha, and detection capability, CCbeta have been calculated for all compounds.

Interaction of a muscarinic cholinergic agonist on acetylcholine and dopamine receptors in the monkey brain studied with positron emission tomography.

The effects on the binding to cholinergic and dopaminergic receptors in the brain during continuous intravenous infusion of the muscarinic cholinergic receptor agonist milameline (CI-979) were studied in the rhesus monkey by means of positron emission tomography. Binding to milameline cholinergic receptors was quantified using the muscarinic receptor antagonist [(11)C]-N-methyl-4-piperidinylbenzilate ([(11)C]NMP), and the effects on nicotine receptor binding were measured with (S)-[(11)C-methyl]nicotine. Changes in the binding of the D(2) dopamine receptor antagonist [(11)C]raclopride were measured as well. The binding of [(11)C]NMP increased in most brain regions with the infusion of increasing doses of milameline from 0.5 to 10 microg/kg/h. (S)-[(11)C-methyl]nicotine binding was unchanged or increased somewhat. Binding of [(11)C]raclopride to the D(2) dopaminergic receptors in the striatum of the brain increased by 10 +/- 4% following 2 microg/kg/h of milameline. The results suggest a possible action of milameline both on presynaptic muscarinic receptor subtypes as well as dopamine levels dependent on the receptor reserve of the muscarinic receptor subtypes.