Format

Send to

Choose Destination
J Anal Toxicol. 2014 Apr;38(3):164-70. doi: 10.1093/jat/bku008. Epub 2014 Feb 10.

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.

Author information

1
Forensic Chemistry Laboratory, Forensic Science Division, Supreme Prosecutors' Office, 157 Banpodaero, Seocho-gu, Seoul 137-730, Republic of Korea.

Erratum in

  • J Anal Toxicol. 2014 Jul-Aug;38(6):385.

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.

PMID:
24519562
DOI:
10.1093/jat/bku008
[Indexed for MEDLINE]

Supplemental Content

Full text links

Icon for Silverchair Information Systems
Loading ...
Support Center