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Differentiation of Structurally Similar Phenethylamines via Gas Chromatography-Vacuum Ultraviolet Spectroscopy (GC-VUV)

NCJ Number
Zackery R. Roberson; John. V. Goodpaster
Date Published
August 2019
11 pages
This study sought to determine the extent to which structurally similar phenethylamines are differentiated, using their vacuum ultraviolet (VUV) spectra.
The vacuum ultraviolet region includes wavelengths shorter than 200-nm. Electronic transitions of sigma and pi bonds lie in this region, which have the potential to yield structural information. Thus, a VUV detector should be able to detect nearly any molecule analyzable by gas chromatography. Phenethylamines are a common drug class, including pseudoephedrine and illicit drugs such as methamphetamine. Several phenethylamines are difficult to analyze by electron impact mass spectrometry due to their fragmentation giving the same mass to charge ratio fragments at similar ratios. Although phenethylamines are generally differentiable by retention time, an extra layer of specificity is preferred in forensic analyses. In the current study. a vacuum ultraviolet (VUV) spectrophotometer coupled to a gas chromatograph was used to collect VUV spectra at high frequency between 125 and 430-nm. Eight phenethylamines were analyzed for this work using GC/VUV. A calibration curve and limit of detection study was performed that indicates a limit of detection around 10-g-mL-1 and an upper limit of linearity around 1000-g-mL-1. The spectra, analyzed by Principal Component Analysis and Discriminant Analysis, indicate the ability to reliably differentiate each of the drugs from one another including structural isomers and diastereomers. Lastly, five "street" samples containing amphetamines were analyzed to demonstrate "real world" performance. (publisher abstract modified)

Date Published: August 1, 2019