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.

Factors Affecting Species Identifications of Blow Fly Pupae Based upon Chemical Profiles and Multivariate Statistics

“…After 4 day, the extracted solution was siylated and submitted to GC-MS analysis via the TV-SPME method described [43]. This method provided excellent sensitivity an order of magnitude greater than what could be achieved by liquid injection, allowing for the analysis of liquid extracts without a reconstitution step.…”

“…The purpose of this project was to interrogate the chemical profiles that could be obtained from pupae by solvent extraction followed by total vaporization solid-phase microextraction (TV-SPME) [43]. The advantage of this method over headspace or immersion SPME is the elimination of the need to determine the optimal organic solvent, and that extracts do not need to be filtered reducing buildup and potential contamination of the GC column.…”

Optimisation of recovery protocols for double-base smokeless powder residues analysed by total vaporisation (TV) SPME/GC-MS

“…This method has been demonstrated as offering greater sensitivity than liquid injection or headspace or immersion SPME [31][32][33], and has been successfully applied to the detection of smokeless powder residues on steel pipe bomb fragments [34]. The optimised parameters were then applied to post-blast residues deposited on witness materials following detonation of a pipe bomb device.…”

Chemical analysis of racing fuels using total vaporization and gas chromatography mass spectrometry (GC/MS)

“…An important note is that the internal volume of a nominal 20 mL headspace vial is actually larger (e.g., 20.9 mL), which has a small but important effect on the calculated volume 8 . The theory and experimental requirements for coupling total vaporization to solid phase microextraction (TV-SPME) have been discussed previously, as well as the application of TV-SPME to determining nicotine in hair and post-blast explosive residue on bomb fragments 7,8 . As with any quantitative SPME method, the temperature and time of exposure of the SPME fiber to the sample vapor must be both accurate and precise, hence the use of an auto-sampler is required.…”