Novel Extractions of Trace-Level Compounds using PDMS Sorbent Polymers for High-Throughput Analyses and Mass Spectral Imaging

Abstract

There is a need for affordable, rapid, trace-level (sub-ppm) chemical technology to characterize large numbers of samples to proactively ensure high-quality and safe agricultural and food products. This is especially true for wine and grapes where large numbers of samples require analyses to assess smoke taint exposure, characterize breeding programs, etc. Solid phase microextraction (SPME) is widely used in conjunction with gas chromatography-mass spectrometry (GC-MS) for volatile analyses in foodstuffs and other complex matrices. However, standard GC-MS quantitation methods generally require ~30-60 min per sample, making it suboptimal for high throughput analyses. Recent work from our lab has developed a method for the selective extraction and pre-concentration of volatiles which uses a planar sorbent sheet (SPMESH) headspace extraction prior to rapid analysis by Direct Analysis in Real Time (DART)-MS. Using this combined SPMESH DART-MS approach, 24 samples could be extracted and analyzed in 45 min with detection limits of common odorants in the ng/L to μg/L range.While the original work using SPMESH-DART-MS was a substantial improvement over SPME-GC-MS, it still has its limitations. First, instead of being limited by a lengthy GC cycle, throughput is now limited by: (1) the equilibration time needed for a headspace extraction, (2) crosstalk within the system limiting the number of useable wells, and (3) the dimensions of the well plate itself. Additionally, the current range of compounds compatible with SPMESH-DART-MS is rather narrow. While SPMESH-DART-MS has previously worked well for non-polar, highly volatile compounds, it has poor performance with semi-polar volatiles and is incompatible with non-volatile compounds in headspace mode. This dissertation will describe efforts to overcome these challenges.