Fiber-Sample Distance, An Important Parameter To Be Considered in Headspace Solid-Phase Microextraction Applications

SPME-GC-MS untargeted metabolomics approach to identify potential volatile compounds as markers for fraud detection in roasted and ground coffee

Roasted ground coffee has been intentionally adulterated for economic revenue. This work aims to use an untargeted strategy to process SPME-GC-MS data coupled with chemometrics to identify volatile compounds (VOCs) as possible markers to discriminate Arabica coffee and its main adulterants (corn, barley, soybean, rice, coffee husks, and Robusta coffee). Principal Component Analysis (PCA) showed the difference between roasted ground coffee and adulterants, while the Hierarchical Clustering of Principal Components (HCPC) and heat map showed a trend of adulterants separation. The partial Least-Squares Discriminant Analysis (PLS-DA) approach confirmed the PCA results. Finally, 24 VOCs were putatively identified, and 11 VOCs are candidates for potential markers to detect coffee fraud, found exclusively in one type of adulterant: coffee husks, soybean, and rice. The results for possible markers may be suitable for evaluating the authenticity of ground-roasted coffee, thus acting as a coffee fraud control and prevention tool.

A volatilomics analytical protocol employing solid phase microextraction coupled to GC × GC-MS analysis and combined with multivariate chemometrics for the detection of pomegranate juice adulteration

In this work, a solid-phase microextraction (SPME) method combined with two-dimensional gas chromatography coupled to mass spectrometry (GC × GC-MS) was optimized and used to assess the authenticity of pomegranate juice to prevent fraudulent practices. A divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) fiber was used for the extraction of the volatiles. The critical parameters that affect the extraction process, such as the sample volume, and the extraction time were studied. The optimized protocol involved the addition of 15 mL of juice in 50 mL vial and saturation with 30% w/v NaCl.The extraction was carried out within 45 min under 1000 rpm stirring and was applied in the analysis of real juice samples to assess authenticity and detect low levels of pomegranate juice adulteration with grape and apple juice down to 1%. Commercially available pomegranate juice samples were acquired (n1 = 6) and adulterated with 1% of apple juice (n2 = 6), 1% of grape juice (n3 = 6), and a mixture of 1% apple juice and 1% grape juice (n4 = 6). Authentic pomegranate juice samples and adulterated mixtures were analyzed by SPME-GC × GC-MS. The analysis resulted in the identification of 123 volatile compounds that were further processed with chemometric tools. Principal component analysis (PCA) was employed to visualize the clustering of the samples, and a two-way orthogonal partial least squares discriminant analysis (O2PLS-DA) chemometric model was developed and successfully classified the samples to authentic pomegranate juice or adulterated with an explained total variance of 87.4%. The O2PLS-DA prediction model revealed characteristic volatile markers that could be used to detect pomegranate juice fraud.

Development of a solid phase microextraction method for the determination of nicotine in dried mushrooms

Official control of EU market foodstuffs repeatedly reports high nicotine levels in dried wild mushrooms without any clear scientific consensus about their origin. The advised constant monitoring calls for improvements to existing methods. For this purpose, our aim was to develop a headspace solid phase microextraction (HS-SPME) method coupled to gas chromatography with mass spectrometric detection (GC-MS) that would eliminate the need for extensive sample pre-treatment. The type of fiber coating, amount of sample, extraction temperature and time, desorption time and salt addition were investigated and optimized as parameters affecting the SPME procedure. The optimized conditions were used to validate a quantitative method for nicotine analysis by matrix-matched calibration and isotopically labelled internal standard correction. The method provided good linearity (r2 = 0.9994) over the tested concentration range (0.025-1 mg kg-1), low detection limit (0.005 mg kg-1) and low quantification limit (0.017 mg kg-1) for nicotine, being below the EU foodstuff regulations. For both of the tested concentration levels (0.050 and 0.200 mg kg-1), precision expressed as relative standard deviation was below 10% (4.5% and 8.5%, respectively), while accuracy was 98.2% and 100.3%. The optimized method was then used to determine nicotine levels in 18 samples of dried Boletus mushrooms from southeastern European countries entering the EU market. We demonstrated our HS-SPME procedure to be fast, simple, sensitive, solvent-free, cost-effective and thus suitable for controlling consumer safety regarding nicotine level in dried mushrooms.

Dynamic headspace solid-phase extraction at room temperature: a theoretical model, method, and application for propofol analysis

Herein, a simple dynamic headspace solid-phase extraction (DHS-SPE) process at room temperature was used for a material that is sensitive to increase in the temperature. A proposed method was implemented to rapidly extract propofol (PF) from a complex matrix before fluorescence spectroscopy analysis, within a short sampling time without involving a hot plate or stirrer. A mini diaphragm pump was used to circulate the headspace gas. As the headspace gas flows over the sample solution surface, bubbles form and release analytes from the liquid into the headspace. During the extraction process, the headspace gas passes through the coated metal foam as a sorbent that is placed in a homemade glass vessel and analytes are trapped from the gas phase. A theoretical model of DHS-SPE based on the consecutive first-order process is proposed in this study. A mathematical solution for the dynamic process of mass transfer was obtained by correlating the variation in analyte concentration in the headspace and adsorber with the pump speed and amount of analyte extracted to the solid phase. Using electrochemically Nafion-doped polypyrrole (PPy-Naf) film on nickel foam as the solid-phase coupled to fluorescence detection, a linear dynamic range over the concentration range of 100-500 nM with a detection limit of 15 nM was obtained. This method was applied successfully for PF determination in human serum sample matrices without the interference of co-administered drugs, such as cisatracurium, which have significant emission spectrum overlap. The developed method can lead to a new idea for sample pretreatment, which is compatible with many analytical techniques and has been successfully combined with fluorescence spectroscopy in this work. This format of sampling simplifies the transfer of analytes from complex matrices to the headspace for the extraction and preconcentration process, eliminating the heating step and the need for expensive equipment.

Gas-cycle-assisted headspace solid-phase microextraction coupled with gas chromatography for rapid analysis of organic pollutants

Herein, a new gas-cycle-assisted (GCA) headspace solid-phase microextraction (HS-SPME) device was designed to rapidly extract organic pollutants with high K_ow and boiling points, which have difficulty in volatilization from matrix to headspace. Organic pollutants, including three polycyclic aromatic hydrocarbons (PAHs), four polychlorinated biphenyls (PCBs), and five phthalate esters (PAEs), were selected to evaluate the performance of GCA HS-SPME. Compared with conventional HS-SPME, the equilibrium times of GCA HS-SPME for extraction of PAHs, PCBs, and PAEs were greatly shortened from 70-90 to 5-11 min. Moreover, the limits of detection for analysis of PAHs were achieved at pg mL^-1 level by GCA HS-SPME coupled with gas chromatography-flame ionization detection.

Characterization of the Aroma Profile and Main Key Odorants of Espresso Coffee

Espresso coffee (EC) is a common coffee preparation technique that nowadays is broadly widespread all over the globe. Its popularity is in part attributed to the intense aroma and pleasant flavor. Many researchers have studied and reviewed the aroma of the coffee, but there is a lack of specific review focused on EC aroma profile even if it is intensively investigated. Thus, the objective of the current review was to summarize the aroma profile of EC and how different preparation variables can affect EC flavor. Moreover, a collection of diverse analytical procedures for volatile analysis was also reported. The findings of this survey showed that the volatile fraction of EC is extremely complex, but just some compounds are responsible for the characteristic aroma of the coffee, such as some aldehyde, ketones, furanones, furans, sulfur compounds, pyrazines, etc. In addition, during preparation, some variables, e.g., temperature and pressure of water, granulometry of the coffee particle, and brew ratio, can also modify the aroma profile of this beverage, and therefore its quality. A better understanding of the aroma fraction of EC and how the preparation variables should be adjusted according to desired EC would assist coffee workers in obtaining a higher quality product.

Quantification of Volatile Compounds in Wines by HS-SPME-GC/MS: Critical Issues and Use of Multivariate Statistics in Method Optimization

The aim of this review is to explore and discuss the two main aspects related to a HeadSpace Solid Phase Micro-Extraction Gas-Chromatography/Mass-Spectrometry (HS-SPME-GC/MS) quantitative analysis of volatile compounds in wines, both being fundamental to obtain reliable data. In the first section, recent advances in the use of multivariate optimization approaches during the method development step are described with a special focus on factorial designs and response surface methodologies. In the second section, critical aspects related to quantification methods are discussed. Indeed, matrix effects induced by the complexity of the volatile profile and of the non-volatile matrix of wines, potentially differing between diverse wines in a remarkable extent, often require severe assumptions if a reliable quantification is desired. Several approaches offering different levels of data reliability including internal standards, model wine calibration, a stable isotope dilution analysis, matrix-matched calibration and standard addition methods are reported in the literature and are discussed in depth here.

Nitrogen-doped porous biochar derived from marine algae for efficient solid-phase microextraction of chlorobenzenes from aqueous solution

Nitrogen-doped porous biochar (NPB) with a large specific surface area, wide pore size distribution, graphitized structure, nitrogen doping, and hydrophobicity was fabricated by high-temperature modification of algal biochar with potassium carbonate. This NPB was then uniformly coated on stainless steel wire as a novel solid-phase microextraction (SPME) fiber. The extraction efficiency of NPB-coated fiber for seven chlorobenzenes (CBs) was excellent; it was 1.0-112.2 times higher than that of commercial SPME fibers. A trace determination method was developed for seven CBs in water with the optimized extraction conditions by NPB-coated fiber and gas chromatography-electron capture detector, which showed wide linear ranges (1-1000 ng L^-1), low detection limits (0.007-0.079 ng L^-1), great repeatability (2.5-6.5% for intra-day, and 3.1-6.8% for inter-day), and excellent reproducibility (3.5-6.3%, n = 5). The practicality of the developed method was evaluated using real water samples and showed great recoveries (89.55-105.19%). This study showed that low-cost biomass wastes could be converted to advanced biochar materials by a facile method, and displayed excellent performance in SPME applications.

An unattended HS-SPME-GC-MS/MS combined with a novel sample preparation strategy for the reliable quantitation of C8 volatiles in mushrooms: A sample preparation strategy to fully control the volatile emission

Eight carbon (C8) compounds are the key characteristic flavors of mushrooms. The quantitative analysis of the volatiles in mushrooms is challenging especially with the unattended HS-SPME-GC-MS. An unattended HS-SPME-GC-MS/MS in combination with novel sample preparation of the complete control of volatile emissions was developed for the quantitation of the C8 volatiles in mushrooms. The sample preparation strategy was composed of freeze-drying, rehydration, and the addition of a 15% citric acid solution. With this strategy, the volatile emission from mushroom was fully controlled at a certain time point. This method was found to be highly reliable, sensitive, precise, and accurate. This method was successfully applied to measure the contents of the C8 volatiles in the beech, button, and shiitake mushrooms. 1-Octene-3-ol was the most predominant compound in the mushrooms, representing 62.4, 69.0, and 89.2% of the total C8 volatiles in the beech, button, and shiitake mushrooms, respectively.

An Overview on Truffle Aroma and Main Volatile Compounds

Truffles are underground edible fungi that grow symbiotically with plant roots. They have been globally considered as one of the most expensive foods because of their rarity, unique aroma, and high nutritional value as antioxidant, anti-inflammatory, antiviral, hepatoprotective, anti-mutagenic, antituberculoid immunomodulatory, antitumor, antimicrobial, and aphrodisiac. The unique flavor and fragrance of truffles is one of the main reasons to get worldwide attraction as a food product. So, the aim of this review was to summarize the relevant literature with particular attention to the active aroma components as well as the various sample preparation and analytical techniques used to identify them. The major analytical methods used for the determination of volatile organic compounds (VOC) in truffles are gas chromatography (GC), proton-transfer-reaction mass spectrometry (PTR-MS), and electronic nose sensing (EN). In addition, factors influencing truffle aroma are also highlighted. For this reason, this review can be considered a good reference for research concerning aroma profiles of different species of truffles to deepen the knowledge about a complex odor of various truffles.

Development of functional whey cheese enriched in vitamin D3: nutritional composition, fortification, analysis, and stability study during cheese processing and storage

"Ricotta" cheese is a traditional and popular Italian fresh whey cheese commonly produced from cow's milk. Food fortification is an efficient strategy to reduce the high global prevalence of vitamin D deficiency. This study aims to study the chemical-nutritional analysis of ricotta cheese and to assess its suitability as a dairy matrix for vitamin D fortification. The chemical-nutritional analyses revealed that ricotta cheese is a good source of proteins (7.8 g/100 g) with high levels of branched-chain amino acids (1.8 g/100 g). Moreover, ricotta contains high levels of calcium (0.4 g/100 g) and phosphorus (0.2 g/100 g). 50 mg of vitamin D₃ were added to 95 kg of cheese reaching a mean fortification level of 41.4 ± 4.0 µg/100 g of ricotta cheese. The fortification study showed that vitamin D homogenously distributes in ricotta cheese after the homogenisation process. Moreover, vitamin D₃ has high heat stability (93.8 ± 1.8%) and remains stable throughout the shelf-life of the fortified food. This study demonstrates that ricotta cheese represents an ideal alternative dairy matrix for vitamin D₃ fortification.