EVIDENCE LIBRARY
How Two-Dimensional Gas Chromatography Separates Drugs in Urine
A forensic validation study separated 12 target drugs in spiked urine using two gas chromatography columns and flame ionization detection.
A urine sample can contain several compounds that leave a chromatography column at nearly the same time. Chandra Siri and colleagues tested whether a second column could improve separation for a panel of 12 psychoactive substances, including methamphetamine, methadone, ketamine and cocaine. The method used a nonpolar first column and a polar second column, followed by flame ionization detection.
What the validation established
Under the study conditions, the team achieved baseline separation of the targets in a urine matrix within eight minutes. The reported detection limits ranged from 10 to 20 ng/mL, while the calibration range began at 50 ng/mL. A detection limit describes the method’s ability to distinguish a signal. The calibration range describes the concentrations over which the team evaluated the quantitative response.
The researchers tested urine spiked with known amounts of the target compounds. The results show how the panel performed against those materials under controlled conditions. In casework, interpreting an unexpected peak would also require the laboratory’s identification criteria and evidence that the method can distinguish the target from relevant interferents.