title: Quantitative analysis of lignocaine and metabolites in equine urine and plasma by liquid chromatography-tandem mass spectrometry.
abstract: In this paper, a method for the sensitive and reproducible analysis of lignocaine and its four principal metabolites, monoethylxylidide (MEGX), glycylxylidide (GX), 3-hydroxylignocaine (3-HO-LIG), 4-hydroxylignocaine (4-HO-LIG) in equine urine and plasma samples is presented. The method uses liquid chromatography coupled to tandem mass spectrometry operating in electrospray ionisation positive ion mode (+ESI) via multiple reaction monitoring (MRM). Sample preparation involved solid-phase extraction using a mixed-mode phase. The internal standard adopted was lignocaine-d(10). Lignocaine and its metabolites were successfully resolved using an octadecylsilica reversed-phase column using a gradient mobile phase of acetonitrile and 0.1% (v/v) aqueous formic acid at a flow rate of 300 microL/min. Target analytes and the internal standard were determined by using the following transitions; lignocaine, 235.2>86.1; 3-HO-LIG and 4-HO-LIG, 251.2>86.1; MEGX, 207.1>58.1; GX, 179.1>122.1; and lignocaine-d(10), 245.2>96.1. Calibration curves were generated over the range 1-100 ng/mL for plasma samples and 1-1000 ng/mL for urine samples. The method was validated for instrument linearity, repeatability and detection limit (IDL), method linearity, repeatability, detection limit (MDL), quantitation limit (LOQ) and recovery. The method was successfully used to analyse both plasma and urine samples following a subcutaneous administration of lignocaine to a thoroughbred horse.
authors.affiliation: Racing Science Centre, PO Box 513, Albion, Queensland 4010, Australia. samantha.nelis@racing.qld.gov.au
authors.forename: Samantha A
authors.initials: SA
authors.lastname: Nelis
authors.forename: Catherine
authors.initials: C
authors.lastname: Sievers
authors.forename: Mark
authors.initials: M
authors.lastname: Jarrett
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Nissen
authors.forename: Carl M J
authors.initials: CM
authors.lastname: Kirkpatrick
authors.forename: P Nicholas
authors.initials: PN
authors.lastname: Shaw
mesh_terms: D000818:Animals; D002853:Chromatography, Liquid / Q000379:methods* / Q000662:veterinary; D006736:Horses / Q000097:blood / Q000378:metabolism / Q000652:urine; D008012:Lidocaine / Q000097:blood* / Q000378:metabolism / Q000652:urine*; D057230:Limit of Detection; D053719:Tandem Mass Spectrometry / Q000379:methods* / Q000662:veterinary; D019155:Veterinary Drugs / Q000097:blood* / Q000378:metabolism / Q000652:urine*
chemical_list: D019155:Veterinary Drugs; D008012:Lidocaine