RAPID, REPEATABLE, AND ROBUST ANALYSIS OF TRACE LEVEL VOLATILE ORGANIC COMPOUNDS USING PLANAR HEADSPACE EXTRACTION GEOMETRIES COUPLED TO CHROMATOGRAPHY-FREE AMBIENT IONIZATION-MASS SPECTROMETRY: SOLID PHASE MICROEXTRACTION SHEETS AND BEYOND
The routine analysis of trace-level volatile (VOCs) and semi-volatile organic (SVOCs) compounds by gas chromatography – mass spectrometry (GC-MS) is relied on by many fields for simple detection, routine profiling, and quantitation of analytes with varying physicochemical properties. Conventional GC-MS relies on extraction geometries and separations not well suited for high-throughput analyses. This work describes the development and validation of rapid methods for key trace level aroma compounds from food matrices. Planar thin film microextraction devices (e.g., Solid Phase Mesh Enhanced Sorption from Head Space (SPMESH)) allow for parallelized extractions leading to substantial improvements in throughput compared to conventional approaches. Such extraction geometries are easily coupled to ambient ionization-mass spectrometry (AI-MS) for quantitative analysis, leading to further increases to throughput by eliminating chromatographic separation prior to identification. Direct HS analysis requires sufficient volatility and physicochemical properties amenable to both extraction by the extractive phase and to ambient ionization (AI) techniques. Current SPMESH approaches are limited to highly hydrophobic polydimethylsilicone (PDMS) as an extractive phase. This work demonstrates and validates the direct analysis of a volatile, low-polarity odorant (3-isobutyl-2-methoxypyrazine (IBMP)) using SPMESH extraction followed by AI coupled to multiple detector platforms (e.g., High resolution MS, triple quadrupole MS) in around 2 min per sample. The linearity, repeatability, and limits of detection for this method demonstrate it as a good alternative to traditional chromatography-based approaches that require between 30 and 60 minutes per sample. For analysis of polar and reactive analytes (aldehyde, volatile phenols) in-situ derivatization prior to SPMESH-DART-MS was demonstrated for the first time. Derivatization with O-2,3,4,5,6-pentafluorohydroxylamine (PFBHA) is performed for C6 aldehydes (hexanal, (E)-2-hexenal) with linearity, repeatability, limits of detection, and accuracy comparable to conventional methods. For volatile phenols, a deuterated acetylation agent (d6-acetic anhydride) increased sensitivity and resolved isobaric interferences- a common challenge in chromatography free analysis methods- present in non-labelled acetylated derivatives.