We develop and evaluate dynamic headspace sampling methods to capture and concentrate vapors from single components (solid or liquid) to determine vapor pressures. These measurements provide high-quality data for process models. We also capture and analyze headspace vapor from complex, multicomponent matrices to provide information for forensic science applications.
Vapor pressures of unstable, reactive compounds. Over the last decade, our group has investigated a variety of low-volatility compounds including taggants (found in explosives), biofuels, terpenes and cannabinoids. Our technique, PLOT-cryoadsorption, is a small-volume dynamic headspace sampling approach similar to purge-and-trap methods. It was developed at NIST and has been used for numerous applications. PLOT-cryoadsorption has recently been improved and re-branded Dynamic Vapor Microextraction (DVME). Our current focus on cannabis constituents provides some of the necessary measurement science for the development of a cannabis breathalyzer.
Lovestead, T. M. and Bruno, T.J., 2017. Determination of cannabinoid vapor pressures to aid in vapor phase detection of intoxication, Forensic Chemistry 5, 79-85, https://doi.org/10.1016/j.forc.2017.06.003.
Widegren, J. A., C. E. Beall, A. E. Tolbert, T. M. Lovestead and Bruno, T.J., 2016. The use of antioxidants to improve vapor pressure measurements on compounds with oxidative instability: methyl oleate with tert-butylhydroquinone. Journal of Chemical & Engineering Data 62, 539-546, https://doi.org/10.1021/acs.jced.6b00821.
Widegren, J. A., Harvey, A. H., McLinden, M. O. and Bruno, T.J., 2015. Vapor pressure measurements by the gas saturation method: the influence of carrier gas. Journal of Chemical & Engineering Data 60(4), 1173 - 1180, https://doi.org/10.1021/je500865j.
Widegren, J. A. and Bruno, T.J., 2010. Vapor pressure measurements on low-volatility terpenoid compounds by the concatenated gas saturation method. Environmental Science & Technology 44, 388-393, https://doi.org/10.1021/es9026216.
Partitioning of cannabis compounds. This new project investigates the distribution of compounds between two phases of interest such as blood/air (important for breath analysis) or air/sorbent (important for indoor air sampling) with measurements and models.
Jeerage, K. M. and Holland, E. N., Predicting sorbent-air partition coefficients for terpenoids at multiple temperatures, submitted.
Fire debris analysis. When arson is suspected at the scene of a fire, burned debris is collected and returned to the lab to be analyzed for residues of ignitable liquids (fuels) that may have played a role in the fire. Using PLOT-cryoadsorption, we have detected residual accelerants from simulated fire debris and have studied the capability of our distillation curve measurements to predict the thermal weathering processes that a fuel undergoes during a fire. Our current focus is directly comparing dynamic and passive headspace concentration methods for extracting ignitable liquid residue from simulated fire debris.
Nichols, J. E., Harries, M. E., Lovestead, T. M. and T. J. Bruno, 2014. Analysis of arson fire debris by low temperature dynamic headspace adsorption porous layer open tubular columns, Journal of Chromatography A 1334, 126-138, https://doi.org/10.1016/j.chroma.2014.01.080.
Bruno, T. J., Lovestead, T. M. and M. L. Huber, 2011. Prediction and preliminary standardization of fire debris analysis constituents with the advanced distillation curve method, Journal of Forensic Sciences 56, S191-S202, https://doi.org/10.1111/j.1556-4029.2010.01628.x.
Identification of headspace compounds from other complex matrices. Beyond vapor pressure measurements, we have used our vapor sampling approaches qualitatively to characterize the headspace compounds found in complex, real-world samples that are significant for public health and safety reasons: explosives, spoiled food, and cadavers.
Lovestead, T. M. and T. J. Bruno, 2011. Detecting gravesoil with headspace analysis with adsorption on short porous layer open tubular (PLOT) columns, Forensic Science International 204(1-3), 156-161, https://doi.org/10.1016/j.forsciint.2010.05.024.
Lovestead, T. M. and T. J. Bruno, 2010. Detection of poultry spoilage markers from headspace analysis with cryoadsorption on short alumina PLOT columns, Food Chemistry 121(4), 1274-1282, https://doi.org/10.1016/j.foodchem.2010.01.044.
Lovestead, T. M. and T. J. Bruno, 2010. Trace headspace sampling for quantitative analysis of explosives with cryoadsorption on short alumina PLOT columns, Analytical Chemistry 82(13), 5621–5627, https://doi.org/10.1021/ac1005926.