Date of Award

6-2026

Document Type

Thesis

Degree Name

Master of Science (MS)

Department/Program

Forensic Science

Language

English

First Advisor or Mentor

Marta Concheiro-Guisan

Second Reader

Ana Pego

Third Advisor

Michelle Carlin

Abstract

Ethanol is a highly encountered drug by forensic toxicologists and is eliminated from the bloodstream rapidly in under 12 hours. Direct biomarkers, ethyl glucuronide (EtG), ethyl sulfate (EtS), and phosphatidylethanol (PEth), can extend the detection window of alcohol consumption, with PEth having the longest of 2 to 4 weeks in whole blood (WB) and dried blood spots (DBS). The goal of this study was to compare PEth in WB and DBS, EtS in oral fluid and EtG/EtS in urine to detect ethanol use. Two major PEth homologs, POPEth and PLPEth, were analyzed on HemaXis DB10 cards (n = 267), extracted with methanol and analyzed using liquid chromatography-tandem mass spectrometry. The rest of the samples were analyzed at Quest and at Sam Houston State University. Of the DBS samples, 78.3% were positive for POPEth (average concentration 42.7 ng/mL, range 5.2 to 223.5 ng/mL). For PLPEth, 80.1% of the samples were positive (mean 40.7 ng/mL, range 4.4 to 209.1 ng/mL). Quantitatively comparison with WB, in which 14.9% of samples were positive for both POPEth and PLPEth, shows that DBS is more sensitive. Oral fluid returned one positive sample for EtS. Urine testing for EtG and EtS had more positive results than oral fluid, with a 3.3% positivity rate, but it is still lower than DBS PEth rates. PEth in DBS was demonstrated to be the most sensitive approach to detect ethanol exposure.

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