Date of Award


Document Type


Degree Name

Master of Science (MS)


Forensic Science



First Advisor or Mentor

Marta Concheiro-Guisán

Second Reader

Ana Pego

Third Advisor

Michelle Carlin


The expanded use of recreational and medicinal cannabis products, as well as the appearance of new cannabinoid derivatives, increases the importance of implementing pre-analytical (sample collection) protocols and the development of recommendations for cannabinoid testing in biological samples. The accurate quantification of cannabinoids in biological samples is critical for providing a correct result interpretation, especially if specific thresholds have been legally set, as in drugs and driving cases in certain states. Previous studies have mainly focused on the impact of time and temperature on the stability of delta-9-tetrahydrocannabinol (delta-9-THC) and metabolites in blood samples; however, the influence of the type of blood collection tube has been frequently overlooked, and no studies investigated the stability of delta-8-THC and metabolites in this type of samples. This study focused on the impact of different preservatives and anticoagulants in the analysis of delta-9-THC, delta-8-THC, cannabidiol (CBD), and their hydroxy (delta-9-THC-OH, delta-8-THC-OH, CBD-OH) and carboxy (delta-9-THC-COOH, delta-8-THC-COOH, CBD-COOH) metabolites in blood samples stored at room temperature (RT) and at 4℃ up to one month. The type of preservatives and/or anticoagulants investigated were: potassium oxalate-sodium fluoride, 3.2% sodium citrate, K2EDTA, and SST. All cannabinoids showed stability issues at room temperature, with citrate blood showing the highest losses and K2EDTA blood with the lowest losses. The most unstable compound was CBD-OH at both storage temperatures. Delta-8 and delta-9-cannabinoids showed similar stability behavior, with delta-8-THC-OH and delta-8-THC being slightly more stable than delta-9-THC-OH and delta-9-THC, respectively. Delta-8 and 9-THC-COOH were found to be the most stable analytes.

Available for download on Thursday, May 22, 2025