When analyzing a suspected illicit drug, investigators typically use a gas chromatograph, which heats the drug, causing a chemical breakdown that may make identification difficult for some drugs. Such analysis is particularly problematic with drugs that tend to break down completely at high temperatures — referred to as “thermally unstable.”
Purdue University scientists, working with the support of an NIJ grant, sought to improve the analysis of thermally unstable drugs through a combination of derivatization [1] and a novel total vaporization solid phase microextraction (TV-SPME) technique. They looked at basic and zwitterionic (molecules containing both positive and negative charges) drugs that are among the most difficult to analyze using gas chromatography.
The researchers, led by chemist John Goodpaster, analyzed 33 drugs and drug variants to compare standard liquid injections to the novel TV-SPME method. They discovered that drugs such as amphetamine, 2C-I (a psychedelic), and lorazepam could be identified with TV-SPME directly. However, other drugs could not and required an additional derivatization step.
The derivatization was done using a modification of the solid phase microextraction in which chemical compounds were collected on a special fiber and then vaporized. Because the fiber was exposed to the derivatization agent prior to being exposed to the substance being analyzed, the derivatization occurred on the fiber. That limited the time needed to perform an analysis of each sample and, the researchers said, could increase the efficiency of the entire process.
In conclusion, the researchers said they had demonstrated the utility of TV-SPME, both with and without optimized on-fiber methods, and noted that “The results for realistic samples were the most promising for drugs analyzed by on-fiber derivation as solutions.” The methods examined during the research could be useful for controlled substance units in forensic science laboratories that must analyze samples both quickly and cost-effectively.
About This Article
The research described in this article was funded by NIJ grant 2015-DN-BX-K058, awarded to the Forensic and Investigative Sciences Program, Indiana University-Purdue University Indianapolis. This article is based on the grantee report “Automated Derivatization and Identification of Controlled Substances via Total Vaporization Solid Phase Microextraction (TV-SPME) and Gas Chromatography/Mass Spectrometry (GC/MS)” by John V. Goodpaster, principal investigator.