title: Measurement uncertainty for the determination of amphetamines in urine by liquid-phase microextraction and gas chromatography-mass spectrometry.
abstract: A gas chromatography-mass spectrometry method for the determination of amphetamines in urine samples by means of liquid-phase microextraction was validated, including calculation of measurement uncertainty. After extraction in the three-phase mode, acceptor phase was withdrawn from the fiber and the residue was derivatized with trifluoroacetic anhydride. The method showed to be very simple, rapid and it required a significantly low amount of organic solvent for extraction. The limits of detection were 10 and 20μg/L for amphetamine and methamphetamine, respectively. The calibration curves were linear over the specified range (20μg/L to 1400μg/L; r(2)>0.99). The method showed to be both precise and accurate and a relative combined uncertainty of 2% was calculated. In order of importance, the factors which were more determinant for the calculation of method uncertainty were: analyte concentration, sample volume, trueness and method precision.
authors.affiliation: Faculty of Pharmaceutical Sciences, University of São Paulo, Brazil. Electronic address: sarahcarobini@usp.br.
authors.forename: Sarah Carobini Werner de Souza Eller
authors.initials: SC
authors.lastname: Franco de Oliveira
authors.affiliation: Faculty of Pharmaceutical Sciences, University of São Paulo, Brazil.
authors.forename: Mauricio
authors.initials: M
authors.lastname: Yonamine
mesh_terms: D000662:Amphetamines / Q000652:urine*; D053593:Forensic Toxicology; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D013287:Illicit Drugs / Q000652:urine*; D059627:Liquid Phase Microextraction; D015203:Reproducibility of Results; D015813:Substance Abuse Detection / Q000379:methods; D016482:Urinalysis
chemical_list: D000662:Amphetamines; D013287:Illicit Drugs
keywords: Amphetamines; Liquid-phase microextraction; Measurement uncertainty; Urine