title: Design and optimization of a total vaporization technique coupled to solid-phase microextraction.
abstract: Solid-phase microextraction (SPME) is a popular sampling technique in which chemical compounds are collected with a sorbent-coated fiber and then desorbed into an analytical instrument such as a liquid or gas chromatograph. Typically, this technique is used to sample the headspace above a solid or liquid sample (headspace SPME), or to directly sample a liquid (immersion SPME). However, this work demonstrates an alternative approach where the sample is totally vaporized (total vaporization SPME or TV-SPME) so that analytes partition directly between the vapor phase and the SPME fiber. The implementation of this technique is demonstrated with polydimethylsiloxane-divinylbenzene (PDMS-DVB) and polyacrylate (PA) coated SPME fibers for the collection of nicotine and its metabolite cotinine in chloroform extracts. The most important method parameters were optimized using a central composite design, and this resulted in an optimal extraction temperature (96 °C), extraction time (60 min), and sample volume (120 μL). In this application, large sample volumes up to 210 μL were analyzed using a volatile solvent such as chloroform at elevated temperatures. The sensitivity of TV-SPME is nearly twice that of liquid injection for cotinine and nearly 6 times higher for nicotine. In addition, increased sampling selectivity of TV-SPME permits detection of both nicotine and cotinine in hair as biomarkers of tobacco use where in the past the detection of cotinine has not been achieved by conventional SPME.
authors.affiliation: Department of Chemistry and Chemical Biology, and Forensic and Investigative Sciences Program, Indiana University Purdue University Indianapolis (IUPUI) , 402 North Blackford Street LD326, Indianapolis, Indiana 46202, United States.
authors.forename: Christina L
authors.initials: CL
authors.lastname: Rainey
authors.forename: Dana E
authors.initials: DE
authors.lastname: Bors
authors.forename: John V
authors.initials: JV
authors.lastname: Goodpaster