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B I Podkowik1, M L Smith, R O Pick
1United States Army Forensic Toxicology Drug Testing Laboratory, Wiesbaden, Federal Republic of Germany, APO New York 09457.
Journal of Analytical Toxicology
|September 1, 1987
Summary
Gas chromatography/mass spectrometry (GC/MS) confirms tetrahydrocannabinol (THC) metabolites. This study shows common diuretics like furosemide can be distinguished from THCA-Me, preventing false positives in drug testing.
Area of Science:
- Forensic Toxicology
- Analytical Chemistry
Background:
- Gas chromatography/mass spectrometry (GC/MS) is standard for confirming tetrahydrocannabinol (THC) metabolites in urine.
- Department of Defense labs analyze 11-nor-delta-9-tetrahydrocannabinol-9-carboxylic acid (THCA) using GC/MS after purification and methylation.
Purpose of the Study:
- To investigate potential interference from furosemide, a common diuretic, in THCA analysis.
- To ensure accurate GC/MS confirmation of THCA and prevent false positives.
Main Methods:
- GC/MS with selected ion monitoring was employed.
- Analysis focused on the chromatographic window and monitored ions for THCA-Me and its trideuterated analog.
- Extraction procedures were evaluated for co-isolation of diuretics.
Main Results:
- Methylated furosemide shares chromatographic and mass spectral characteristics with THCA-Me.
- Furosemide and other diuretics can be distinguished from THCA-Me through careful analysis.
- The findings aid in explaining extraneous peaks and correcting for reagent overutilization.
Conclusions:
- Diuretic interference in THCA testing is manageable and distinguishable.
- Accurate interpretation of GC/MS results is crucial for reliable forensic toxicology.
- Methodological understanding prevents misidentification and ensures legal defensibility of results.