What topics does this cannabis study cover?

This study covers research on: THC, CBD, Addiction, Neuroprotection.

Where was this research published?

Published in Journal of analytical toxicology on January 6, 2026.

How test tubes silently destroy your cannabis results

Q: What did this research study find?

**THC concentrations decreased by 81-84% over three months** when plasma samples were stored in gel separation tubes (*PSTs*), compared to standard non-PST tubes, due to *adsorption* into the gel separator material.

Adsorption of Tetrahydrocannabinol (THC), Metabolites, and Related Cannabinoids During Storage of Plasma Samples in Gel Separation Tubes.

Journal of analytical toxicology • January 6, 2026 • Highly Relevant

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AI Summary

This study reveals a critical laboratory issue that affects the accuracy of cannabis testing results. Researchers discovered that when plasma samples containing THC and related cannabinoids are stored in gel separation tubes (PSTs)—commonly used collection containers—the cannabinoids are absorbed into the gel separator, leading to significantly lower measured concentrations over time. This absorption was measured using liquid chromatography-tandem mass spectrometry, a highly precise analytical technique, at multiple time points over three months.

The findings are substantial: THC concentrations dropped by 81-84% over three months when stored in PSTs compared to standard tubes, while CBD, THC-OH (a major metabolite), and CBN all showed 60-75% reductions. Interestingly, THC-COOH—the primary metabolite that toxicology tests often measure—behaved differently, actually increasing in PSTs while decreasing in standard tubes. These differences were statistically significant, meaning they're not due to chance. The effect occurred at both high and low cannabinoid concentrations, suggesting the problem is consistent across different testing scenarios.

For forensic and medical testing, these results carry important implications. Healthcare providers, law enforcement, and laboratories need to be aware that sample collection tubes directly impact measured cannabinoid levels, potentially leading to misinterpretation of patient results or legal cases. The study emphasizes that proper sample handling protocols and understanding of storage artifacts are essential when interpreting cannabinoid test results, especially in legal or clinical contexts where precise concentrations matter.

💡 Key Findings

THC concentrations decreased by 81-84% over three months when plasma samples were stored in gel separation tubes (PSTs), compared to standard non-PST tubes, due to adsorption into the gel separator material.

High

95%

All major cannabinoids except THC-COOH showed significant reductions in measured concentration during PST storage: CBD decreased 62-69%, THC-OH decreased 63-66%, and CBN decreased 70-75% over three months.

High

95%

THC-COOH (the primary THC metabolite) behaved oppositely, increasing in concentration when stored in PSTs while decreasing in standard tubes, suggesting different chemical interactions with the gel separator.

High

92%

The adsorption effect was consistent across both high and low concentration samples, indicating that sample storage in gel separation tubes systematically underestimates cannabinoid levels in forensic and clinical testing.

High

93%

These findings have critical implications for forensic cannabis cases and clinical interpretation, as measured cannabinoid concentrations may be artificially low by 60-85%, potentially affecting legal cases or medical decisions.

High

88%

📄 Original Abstract

The concentrations of some drugs in biofluids can be affected by different storage conditions, including the type of sample collection tube. This phenomenon has been observed in gel separation tubes, where drug adsorption to the gel separator can lead to the underestimation of the drug`s concentration, thus potentially affecting the interpretation of analytical results. The purpose of this study was to determine if concentrations of tetrahydrocannabinol (THC), its metabolites, and related cannabinoids decrease over time when stored in plasma separation tubes (PSTs) as compared to non-PSTs. Plasma samples with a high concentration [HP-24 ng/mL THC, 150 ng/mL carboxy-THC (THC-COOH), 48 ng/mL hydroxy-THC (THC-OH), 15 ng/mL cannabidiol (CBD), and 15 ng/mL cannabinol (CBN)], and low concentration [LP-5.0 ng/mL THC, 31 ng/mL THC-COOH, 10 ng/mL THC-OH, 3.1 ng/mL CBD, and 3.1 ng/mL CBN] of cannabinoids were stored in PSTs and non-PSTs for analysis by liquid chromatography-tandem mass spectrometry at one-hour, three-day, one-week, two-week, three-week, one-month, two-month, and three-month intervals. Statistically significant differences in cannabinoid concentrations (p < 0.05) were observed between non-PSTs and PSTs. All cannabinoids except THC-COOH showed a greater reduction in concentration when stored in PSTs compared to non-PSTs. In contrast, THC-COOH showed an increase in concentration when stored in PSTs compared to non-PSTs. Over a three-month period, concentrations in PSTs decreased for THC by 84% and 81%, THC-OH by 66% and 63%, CBD by 69% and 62%, and CBN by 75% and 70%, in LP and HP samples, respectively. In conclusion, for forensic cases involving cannabinoids, the adsorption of these compounds should be considered in the toxicological interpretation of samples collected in PSTs.

Paper Type

📄 Research

Publication

Journal: Journal of analytical toxicology
Published: January 6, 2026
PMID: 41496001
DOI: 10.1093/jat/bkag001

Authors (4)

Idris A Abdul University of Toronto, 3359 Mississauga Rd, Mississauga, ON, L5L1C6.
Dale Pon Centre of Forensic Sciences, Toxicology Section, 25 Morton Shulman Avenue, Toronto, ON, M3M0B1.
Chesia Giancola Centre of Forensic Sciences, Laboratory Services, 25 Morton Shulman Avenue, Toronto, ON, M3M0B1.
Karen Woodall University of Toronto, 3359 Mississauga Rd, Mississauga, ON, L5L1C6.