title: Estimation of measurement uncertainty for the quantification of 11-nor-delta 9-tetrahydrocannabinol-9-carboxylic acid and its glucuronide in urine using liquid chromatography-tandem mass spectrometry.
abstract: Recently, the estimation of the measurement uncertainty has become a significant issue in the quality control of forensic drug testing. In the present study, the uncertainty of the measurement was calculated for the quantification of 11-nor-delta 9-tetrahydrocannabinol-9-carboxylic acid (THC-COOH) and its glucuronide conjugate (THC-COOH-glu) in urine using liquid chromatography-tandem mass spectrometry. The procedure was based on liquid-liquid extraction of a volume of urine (800 µL) with ethyl acetate. The sources of uncertainty were identified and classified into four major categories as follows: standard preparation, calibration curve, method precision and bias. The overall contribution of combined standard uncertainty on THC-COOH increased in the order of standard preparation (0.9%), method precision (10.4%), calibration curve (30.3%) and bias (58.4%) and, while calibration curve (53.0%) and bias (40.4%) gave the bigger contributions to the combined standard uncertainty for THC-COOH-glu than method precision and standard preparation, which accounted for 6.3 and 0.3%, respectively. The reliability of a measurement was expressed by stating the expanded uncertainty of the measurement result at 95% confidence level. The concentrations of THC-COOH and THC-COOH-glu in the urine sample with their expanded uncertainties were 10.20 ± 1.14 ng/mL and 25.42 ± 5.01 ng/mL, respectively.
authors: Forensic Chemistry Laboratory, Forensic Science Division, Supreme Prosecutors' Office, 157 Banpodaero, Seocho-gu, Seoul 137-730, Republic of Korea.
authors: Jin Young
authors: JY
authors: Kim
authors: Woonyong
authors: W
authors: Kwon
authors: Hee Seung
authors: HS
authors: Kim
authors: Sungill
authors: S
authors: Suh
authors: Moon Kyo
authors: MK
authors: In
mesh_terms: D002138:Calibration; D002188:Cannabis; D002853:Chromatography, Liquid / Q000379:methods* / Q000592:standards; D013759:Dronabinol / Q000031:analogs & derivatives* / Q000652:urine; D020719:Glucuronides / Q000652:urine*; D006801:Humans; D016014:Linear Models; D059625:Liquid-Liquid Extraction; D008962:Models, Theoretical; D012015:Reference Standards; D015203:Reproducibility of Results; D015813:Substance Abuse Detection / Q000379:methods / Q000592:standards; D019966:Substance-Related Disorders / Q000652:urine; D053719:Tandem Mass Spectrometry / Q000379:methods* / Q000592:standards; D035501:Uncertainty
chemical_list: D020719:Glucuronides; C016780:11-nor-delta(9)-tetrahydrocannabinol-9-carboxylic acid; D013759:Dronabinol