Quantitative analytical gas sampling is of great importance
in
a range of environmental, safety, and scientific applications. In
this article, we present the design, operation, and performance of
a recently developed tabletop terahertz (THz) spectroscopic molecular
sensor capable of rapid (minutes) and sensitive detection of polar
gaseous analytes with near “absolute” specificity. A
novel double-coil absorption cell design and an array of room-temperature
sorbent-based preconcentration modules facilitate quantitative THz
detection of light polar volatile compounds, which often challenge
the capabilities of established gas sensing techniques. Acetone, ethanol,
methanol, acetaldehyde, formaldehyde, and isoprene are detected at
low parts-per-billion to high parts-per-trillion levels. This work
evaluates performance-limiting factors for THz spectroscopy-based
chemical identification: (1) spectral signal to noise and (2) preconcentrator
efficiency.
Inhaled
medications are commonplace for administering bronchodilators,
anticholinergics, and corticosteroids. While they have a defined legitimate
use, they are also used in sporting events as performance-enhancing
drugs. These performance enhancers can be acquired via both legal
(i.e., at a pharmacy through over-the-counter medications or through
a prescription) and illicit (i.e., black market and foreign pharmacies)
means, thus making monitoring procurement impossible. While urine
tests can detect these pharmacological agents hours after they have
been inhaled, there is a significant lag time before they are observed
in urine. Direct detection of these inhaled agents is complicated
and requires a multiplexed approach due to the sheer number of inhaled
pharmacological agents. Therefore, detection of propellants, which
carry the drug into the lungs, provides a simpler path forward toward
detection of broad pharmacological agents. In this paper, we demonstrate
the first use of terahertz spectroscopy (THz) to detect inhaled medications
in human subjects. Notably, we were able to detect and quantitate
the propellant, HFA-134a, in breath up to 30 min after using an asthma
inhaler, enabling the use of a point-of-care device to monitor exhaled
breath for the presence of propellants. We also demonstrate via simulations
that the same approach can be leveraged to detect and identify next-generation
propellants, specifically HFA-152a. As a result, we provide evidence
that a single point-of-care THz sensor can detect when individuals
have used pressure-mediated dose inhalers (pMDIs) without further
modification of the hardware.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.