For most people, sweat is an unwelcome part of their day. In Jan Halamek’s laboratory, it’s an important biometric research tool and sample.
In earlier work, Halámek, a University at Albany forensic chemist, analyzed sweat left behind at a crime scene to determine the number of perpetrators present. Now, Halámek and his colleagues have developed strips that can test the ethanol levels in a person’s sweat to detect their blood alcohol content (BAC)—essentially, a sweat-testing strip that works like a breathalyzer.
The chemistry of the strip relies on two enzymes, alcohol oxidase and horseradish peroxidase. Once the strip comes into contact with an individual, the chemical reaction of the two enzymes to the ethanol in sweat produces a visible color change. The higher concentration of alcohol present, the darker the color intensity.
“There's a direct relationship between ethanol in blood and sweat," Halámek told Forensic. "Through our research, we have shown that as an individual consumes alcoholic beverages, their blood alcohol levels increase at a similar pace to sweat alcohol levels.”
As proof of concept, Halámek’s lab led a controlled drinking study with 26 volunteers. After the study participants consumed several shots of 40 percent vodka to obtain 0.08 percent BAC, more than 100 readings were compared between a professional grade breathalyzer and the sweat sensing strip. The sweat samples showed a strong correlation with the breathalyzer readings, according to results published in a paper in Analytical Chemistry.
While breathalyzers are well-established in the law enforcement community and can provide officers with probable cause to make an arrest, the results are preliminary and often do not hold up as evidence in court. Additionally, breathalyzers can be unreliable in certain situations, such as for diabetic subjects who often have acetone in their breath, or those who have (intentionally or unintentionally) recently used mouthwash or breath fresheners.
To make the most impact in court, there should be as little subjectivity as possible. That’s why Halámek’s lab is working with the university’s Department of Computer Science to develop a smartphone application that would perfectly match the test strip’s color change to BAC level.
“A smartphone application will ideally take out any subjectivity from the user,” Halámek said. “Although the responses are visible by naked eye, the changes in shade of color can be difficult to distinguish. Using an app will also regulate the response from different users and record the report.”
Another flaw of the breathalyzer is it requires a conscious subject, needing a breath to be blown for 10 seconds to perform a reading. On the other hand, the sweat test strip can test for alcohol or drugs in an unconscious person, a characteristic that is extremely helpful for EMTs to administer the correct aid faster and more effectively.
Halámek and colleagues in his lab are currently working with the University at Albany’s police department to gain valuable law enforcement feedback. For example, campus police asked Halámek to consider the use of perfumes and other products people typically use when they are pulled over to mask the smell of drugs and alcohol. Halámek said the campus police are interested in continuing to work with the lab as they further develop the strip, and there will be interactions with additional police departments, as well.
Halámek’s lab is well-known for its contributions to forensic science. The lab has been funded through numerous fellowships and even a three-year grant from the Department of Justice and National Institute of Justice to develop non-invasive sensing concepts, like a sweat test strip, or detection of recent THC use through a fingerprint sample (the latest published research). The lab’s overarching goal is to create a versatile, accurate “field kit” for law enforcement use that could be applied for legal purposes.
Photo: The Halámek lab showcases a prototype of its sweat testing strip. Credit: Scott Freedman/UAlbany