Presented at the 55th Annual Meeting of the American Academy of Forensic Sciences, Chicago, IL, 2003.
GHB Free Acid: I. Solution Formation Studies and Spectroscopic Characterization by 1HNMR and FT-IR
Article first published online: 8 MAR 2006
Journal of Forensic Sciences
Volume 51, Issue 2, pages 321–329, March 2006
How to Cite
DeFrancesco, J. V., Witkowski, M. R. and Ciolino, L. A. (2006), GHB Free Acid: I. Solution Formation Studies and Spectroscopic Characterization by 1HNMR and FT-IR. Journal of Forensic Sciences, 51: 321–329. doi: 10.1111/j.1556-4029.2006.00073.x
- Issue published online: 8 MAR 2006
- Article first published online: 8 MAR 2006
- Received 26 April 2005; and in revised form 21 Aug. 2005; accepted 28 Aug. 2005; published 14 Feb. 2006.
- forensic science;
- GHB free acid;
- γ-hydroxybutyric acid;
- solution spectroscopic analysis;
- sodium oxybate
ABSTRACT: In forensic evidence, γ-hydroxybutyric acid (GHB) has frequently been encountered in one of its salt forms (γ-hydroxybutyrate), but has also been encountered in its free acid form (GHB). Owing to the physical properties, encounters of the free acid have been largely restricted to forensic exhibits comprising aqueous solutions, such as acidic beverages that have been “spiked” or formulated with GHB salts or γ-butyrolactone (GBL). The analysis of GHB free acid presents particular difficulties including the potential for altering the original proportions of GHB free acid, GHB carboxylate, and GBL in the course of analysis, and discrimination between GHB free acid and carboxylate forms. In this work, the formation of GHB free acid in aqueous solutions (water and/or D2O) was studied as a function of solution pH. Proton nuclear magnetic resonance (1HNMR) and Fourier-transform infrared spectrometry (FT-IR) measurements were obtained on freshly prepared mixtures of NaGHB and HCl stock solutions representing a series of points along the GHB titration curve. Both 1HNMR and FT-IR were shown to track the changing proportions of GHB free acid and carboxylate forms as a function of pH, while simultaneously monitoring for the formation of the lactone (GBL). The results were consistent with acid–base conversion behavior for a carboxylic acid. 1HNMR was shown to provide an ideal means for analysis of aqueous-based GHB/GBL forensic exhibits based on simple dilution of the neat liquid exhibit, without altering the original proportions of GHB free acid, carboxylate, and GBL in the samples.