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Related Experiment Video

Updated: Jun 22, 2026

Microdialysis of Ethanol During Operant Ethanol Self-administration and Ethanol Determination by Gas Chromatography

Microdialysis of Ethanol During Operant Ethanol Self-administration and Ethanol Determination by Gas Chromatography

Published on: September 5, 2012

Unreliable alcohol testing in a shipping safety programme.

Anders Helander¹, Charlotte Asker Hagelberg, Olof Beck

¹Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden. anders.helander@ki.se

Forensic Science International

|May 26, 2009

Summary

Unpreserved urine samples can lead to false positives in alcohol testing due to microbial contamination. This study found yeast and bacteria can produce ethanol and ethyl glucuronide (EtG) in stored urine, impacting drug testing programs.

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Published on: January 5, 2018

Area of Science:

Forensic toxicology
Clinical chemistry
Microbiology

Background:

Investigated the reliability of urine alcohol testing within a maritime drug and alcohol testing program.
Examined a case with an unusually high urine ethanol concentration (235 mmol/L) that tested positive for Candida albicans, suggesting post-collection ethanol production.

Observation:

Microbial contamination (yeast and/or bacteria) was prevalent in both ethanol-positive (67%) and ethanol-negative (44%) urines.
Several ethanol-positive samples lacked ethanol metabolites ethyl glucuronide (EtG) and ethyl sulphate (EtS), indicating false positives.
Laboratory experiments demonstrated that bacteria like Escherichia coli can produce ethanol and EtG in glucose-supplemented urines during storage.

Findings:

Routine urine collection and handling procedures in the maritime program resulted in numerous false-positive alcohol test results.
Unpreserved urines stored at room temperature are highly susceptible to microbial interference, leading to inaccurate ethanol measurements.
The presence of microbial growth in urine samples significantly compromises the accuracy of alcohol testing.

Implications:

The findings highlight the unsuitability of unpreserved, uncooled urine for alcohol testing due to microbial interference.
Medico-legal consequences can arise from inaccurate alcohol testing results caused by post-sampling ethanol formation.
Recommendations include implementing stricter protocols for urine sample preservation and storage to ensure testing accuracy.