This publication is a technical note to the white paper “Evolving Approaches and Technologies for Seized Drug Analysis” describing gas chromatography-vacuum ultraviolet spectroscopy (GC-VUV).
This technical note to the white paper “Evolving Approaches and Technologies for Seized Drug Analysis” provides an in-depth explanation of gas chromatography-vacuum ultraviolet spectroscopy (GC-VUV). GC-VUV was first introduced in 2014 as a universal separation and detection technique. It combines chromatographic separation of volatile and semivolatile analytes with spectroscopic detection based on the absorption of light in the UV and VUV regions, with the VUV region being defined as below 200 nm. GC-VUV provides enhanced positional isomer differentiation capabilities compared with gas chromatography–electron ionization mass–spectrometry (GC-EI-MS), particularly for isomers differing in substitution on a benzene ring and certain instances pertaining to aliphatic substitution. VUV detection is considered a universal detection technique in seized drug casework because nearly every chemical species absorbs strongly in the VUV region based on electronic transitions of electrons in single bonds (σ → σ*) and double bonds (π → π*), which provide unique absorption signatures. However, because of the nearly universal absorption in the VUV region, VUV spectra must be collected in a flow cell purged with a nonabsorbing background gas, such as diatomic nitrogen.