HS-SPME-GC-TOFMS Methodology for Verification of Geographical Origin and Authenticity Attributes of Coffee Samples

Increasing consumer awareness of food safety issues requires the development of highly sophisticated techniques for the authentication of food commodities. The food products targeted for falsification are either products of high commercial value or those produced in large quantities. For this reason, the present investigation is directed toward the characterization of coffee samples according to geographical origin attributes. In addition, the current examination is focused on the identification of particular marker compounds that compose the volatile and semivolatile aroma fraction of flavoured and dessert coffees. The conducted research involved the development of a rapid headspace solid phase microextraction (HS-SPME) – gas chromatography – time-of-flight mass spectrometry (GC-TOFMS) method for the verification of geographical origin traceability of coffee samples. As opposed to the utilization of traditional univariate optimization methods, the current study employs the application of multivariate experimental designs to the optimization of extraction-influencing parameters. Hence, the two-level full factorial first-order design aided in the identification of two influential variables: extraction time and sample temperature. The optimum set of conditions for the two variables was 12 min and 55 oC, respectively, as directed by utilization of the Doehlert matrix and response surface methodology. The high-throughput automated SPME procedure was completed under optimized conditions by implementing a single divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) metal fiber with excellent properties of durability, which ensured the complete analysis of coffee samples in sequence. The coffee sample originating from an authentic Brazilian coffee producing region and characterized by rich volatile and semivolatile chromatographic profiles was selected as a reference starting point for data evaluation. The combination of the retention index (RI) system using C8-C40 alkanes and the mass spectral library search was utilized for the confirmation of analyte identity in this reference sample. Twenty-nine volatile and semivolatile compounds selected across the wide range of GC chromatogram were then evaluated in terms of chromatographic peak areas for all samples that are to be submitted to this classification study. The semiquantitative results were submitted to statistical evaluation, namely principal component analysis (PCA) for the establishment of corresponding geographical origin discriminations

Solid phase microextraction coupled to comprehensive two-dimensional gas chromatography–time-of-flight mass spectrometry for metabolite profiling of apples: Potential of non-invasive in vivo sampling assay in characterization of metabolome

The objective of the current research project relies on implementation of solvent-free, green and environmentally friendly solid phase microextraction (SPME) sample preparation alternative in the area of complex sample characterization. The advantages that the technique offers in comparison to traditional methods of sample preparation including solvent-free implementation, short sample preparation times, small sample amount requirements, advanced automation capability and minimization of matrix effects are effectively employed during ex vivo and laboratory investigations of complex samples. More important, the underlying features of the technique including miniaturized format, nonexhaustive extraction recoveries and on-site compatibility were fully exploited in order to investigate the metabolome of biological systems directly on the site. Hence, in vivo SPME extraction format was employed in direct immersion SPME sampling of biological systems, hence eliminating the crucial prerequisites associated with multiple preparative steps and incorporation of metabolism quenching that are encountered during implementation of traditional sample preparation methods in global metabolite analysis. Furthermore, in vivo sampling format was hyphenated to comprehensive two-dimensional gas chromatography – time-of-flight mass spectrometry (GCxGC-ToFMS) for high-resolution sampling of volatile and semivolatile metabolites in ‘Honeycrisp’ apples. The initial stages of the project involved evaluation of performance characteristics of commercial SPME extraction coatings in terms of extraction selectivity, extraction sensitivity and desorption efficiency by employing headspace SPME analysis of both aqueous standards spiked with representative volatile and semivolatile metabolites as well as the apple homogenate. DVB/CAR/PDMS coating was selected on the basis of optimum metabolite coverage and extraction sensitivity and was consequently employed during ex vivo and in vivo sampling assays corresponding to determination of volatile and semivolatile metabolites. The former extraction methodology incorporated appropriate sample preparation steps for quenching metabolic activity so that the relevant metabolome profile is not biased against unstable metabolites and those that are susceptible to inter-metabolite conversions which adversely impact preservation of metabolite identity. The two sample preparation assays were compared in terms of metabolite coverage and analytical precision in order to identify SPME route toward characterization of more representative metabolome and determination of instantaneous and more ‘true’ metabolism snapshoot. This is the first report illustrating the implementation of in vivo direct immersion SPME assay for non invasive determination of endogenous fruit metabolites whose profiles and contents are highly correlated to a multitude of influential fruit quality traits

Capturing Plant Metabolome with Direct-Immersion in Vivo Solid Phase Microextraction of Plant Tissues

This document is the Accepted Manuscript version of a Published Work that appeared in final form in Analytical Chemistry, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://pubs.acs.org/doi/abs/10.1021/acs.analchem.5b03684 .For the first time, an in vivo sampling mode of direct immersion–solid phase microextraction (DI-SPME) was employed to capture the metabolome of living plant specimens, using apple (Malus × domestica Borkh.) as a model system. Metabolites were extracted from apple tissues and introduced by thermal desorption into a comprehensive two-dimensional gas chromatography–time-of-flight mass spectrometry instrument. The feasibility of this sampling approach, based on exploitation of microextraction principles, including negligible depletion of free analyte concentrations, solventless sampling and sample preparation, and on-site compatibility, was determined in global metabolite analysis. Rather than adopting an approach of traditional sample preparation, requiring metabolism quenching and laborious sample preparation, the objective of the study was to capture the metabolome in vivo, evaluate the feasibility of the approach to provide unbiased extraction coverage, and compare analytical precision when different SPME sampling modes are employed. The potential of in vivo DI-SPME in quantitative plant metabolomics was assessed by evaluating changes in metabolic fingerprints in response to fruit maturation. The in vivo SPME sampling approach has been demonstrated as capable of sampling living systems with high reproducibility, considering that nearly 50% of hundreds of evaluated compounds included in the determination of analytical performance met the 15% RSD FDA criterion. Esters were extracted with high repeatability (% RSD for hexyl butanoate and butyl butanoate of 16.5 and 5.9, respectively, from 9 determinations in 3 apples) and found to be upregulated in response to apple fruit maturation.Natural Sciences and Engineering Research Council of Canada (NSERC

Solid-Phase Microextraction in Targeted and Nontargeted Analysis: Displacement and Desorption Effects

An aqueous multicomponent mixture containing a wide range of volatility and polarity compounds (log <i>K</i>_ow range 1.26–8.72) was used to clearly define the capabilities and limitations of headspace solid-phase microextraction in quantification of multicomponent complex samples. Commercially available fiber coatings were evaluated by investigating the extraction efficiency and desorption carryover. Comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry was selected to map out the differences between the coatings. The investigated components were chosen to represent several homologous groups of metabolites most frequently present in complex food and environmental samples, including straight-chain hydrocarbons, primary alcohols, secondary alcohols, 2-ketones, aldehydes, ethyl esters, and terpenes. Particular emphasis was placed on examination of coating saturation and interanalyte displacements. These effects were assessed by evaluating the linear dynamic range obtained for spiked aqueous samples with divinylbenzene/Carboxen/poly­(dimethylsiloxane) fiber. This coating was found to provide the optimum extraction coverage and sensitivity for the widest range of analytes. Displacement investigations were extended to apple homogenate characterized by high chemical diversity. The results indicate that interanalyte displacements are infrequent in the naturally occurring samples considered in this study. When displacements take place, they tend to occur for analytes characterized by small distribution constants, and they can be effectively detected by adding such compounds to the sample and corrected by selecting a shorter extraction time

Low temperature SPME device: A convenient and effective tool for investigating photodegradation of volatile analytes

Summarization: Hexachlorobenzene (HCB), a model volatile compound, was exposed to UV irradiation (16 W, 254 nm) after being sorbed in an internally cooled or low temperature solid-phase microextraction (LT-SPME) fibre. Photolysis took place directly on the polydimethylsiloxane coating of the LT-SPME fibre, yielding an “in situ” generation of photoproducts. Maintaining the temperature of the cold fibre at 0 °C eliminated, for the first time, problems of analyte losses due to volatilisation, inherent to the conventional room temperature photo-SPME studies. During the present studies, nearly complete photoremoval of HCB could be achieved within 20 min of irradiation. Photoreduction through photodechlorination was shown to be the main decay pathway in which lesser chlorinated congeners were sequentially formed as intermediates. Accordingly, initial generation of pentachlorobenzene was followed in order from 1,2,3,5-tetrachlorobenzene, 1,2,4,5-tetrachlorobenzene and 1,3,5-trichlorobenzene.Παρουσιάστηκε στο: Journal of Photochemistry and Photobiology A: Chemistr

Detection Of Extraction Artifacts In The Analysis Of Honey Volatiles Using Comprehensive Two-dimensional Gas Chromatography.

Extraction using headspace solid phase microextraction (HS-SPME) coupled to comprehensive two-dimensional gas chromatography with flame ionisation detection (GC×GC-FID) was employed to evaluate the effect of SPME fractionation conditions (heating time and temperature) on the generation of artifacts. The occurrence of artifacts was more pronounced at higher fractionation temperatures and times which caused significant changes in the chromatographic profiles. The identification of the volatile fraction of the honey blend was performed through a two-dimensional gas chromatograph coupled to a mass spectrometer with time of flight analyser (GC×GC-ToFMS) by comparing the first dimension linear temperature programmed retention index ((1)D-LTPRI) with the peak's identities provided by the mass spectral similarity search. Several artifacts were found and identified - such as hydroxymethylfurfural, methyl-furone and furfural - and some of them were not previously detected as such in honey samples. These compounds were either the result of hydrolysis or thermal decomposition of components already present in the honey samples. This occurrence was attributed to the increased detectability provided by GC×GC compared to conventional GC. The possible emergence of previously unknown extraction artifacts as a general tendency related use of GC×GC instead of conventional GC is discussed as a result of these observations.1411828-3