Recent Developments of Stir Bar Sorptive Extraction for Food Applications: Extension to Polar Solutes

Microextraction Techniques for Sample Preparation of Amphetamines in Urine: A Comprehensive Review

Psychological disorders and dramatic social problems are serious concerns regarding the abuse of amphetamine and its stimulant derivatives worldwide. Consumers of such drugs experience great euphoria along with serious health problems. Determination and quantification of amphetamine-type stimulants are indispensable skills for clinical and forensic laboratories. Analysis of low drug doses in bio-matrices necessitates applications of simple and also effective preparation steps. The preparation procedures not only eliminate adverse matrix effects, but also provide reasonable clean-up and pre-concentration benefits. The current review presents different methods used for sample preparation of amphetamines from urine as the most frequently used biological matrix. The advantages and limitations of various sample preparation methods were discussed focusing on the miniaturized methods.

Rapid and Online Microvolume Flow-Through Dialysis Probe for Sample Preparation in Veterinary Drug Residue Analysis

A rapid and online microvolume flow-through dialysis probe designed for sample preparation in the analysis of veterinary drug residues is introduced. This study addresses the need for efficient and green sample preparation methods that reduce chemical waste and reagent use. The dialysis probe integrates with liquid chromatography and mass spectrometry (LC-MS) systems, facilitating automated, high-throughput analysis. The dialysis method utilizes minimal reagent volumes per sample, significantly reducing the generation of solvent waste compared to traditional sample preparation techniques. Several veterinary drugs were spiked into tissue homogenates and analyzed to validate the probe's efficacy. A diagnostic sensitivity of >97% and specificity of >95% were obtained for this performance evaluation. The results demonstrated the effective removal of cellular debris and particulates, ensuring sample integrity and preventing instrument clogging. The automated dialysis probe yielded recovery rates between 27 and 77% for multiple analytes, confirming its potential to streamline veterinary drug residue analysis, while adhering to green chemistry principles. The approach highlights substantial improvements in both environmental impact and operational efficiency, presenting a viable alternative to conventional sample preparation methods in regulatory and research applications.

Superior high-efficiency and high-throughput volatile flavor extraction of Japanese fermented seasonings by solvent-assisted stir bar solid extraction with reverse extraction

Fermented seasonings have pleasant flavors that stimulate our appetite. Their flavoring properties change depending on factors such as their materials and fermented conditions. Therefore, a comparative analysis of their flavor is important when evaluating their quality. However, seasonings contain high levels of various matrices such as sugars, proteins, lipids, and ethanol, making it difficult to extract aroma compounds efficiently from them. In this study, we verified a high-efficient and high-throughput volatile flavor analysis of fermented seasonings by solvent-assisted stir bar solid extraction (SA-SBSE) with reverse extraction. We applied SA-SBSE to Japanese fermented seasonings, soy sauce, miso (fermented beans), and mirin (sweet rice wine) and compared their profiles with those from other common extraction methods, headspace gas-solid-phase microextraction (HS-SPME), liquid extraction with solvent-assisted flavor evaporation (LE-SAFE), and conventional SBSE (C-SBSE). The aroma properties and profiles of extracts from SA-SBSE were close to those of the original sample, being similar to that of LE-SAFE. In addition, potent aroma compounds in each sample were extracted by SA-SBSE and LE-SAFE, which were far superior to those by C-SBSE. For quantification, SA-SBSE extracts showed a good standard curve by the standard addition method. We could quantify maltol, one of the most common potent aroma compounds in all samples, for various commercial samples by such high-throughput analysis.

Application of Sorbent-Based Extraction Techniques in Food Analysis

This review presents an outline of the application of the most popular sorbent-based methods in food analysis. Solid-phase extraction (SPE) is discussed based on the analyses of lipids, mycotoxins, pesticide residues, processing contaminants and flavor compounds, whereas solid-phase microextraction (SPME) is discussed having volatile and flavor compounds but also processing contaminants in mind. Apart from these two most popular methods, other techniques, such as stir bar sorptive extraction (SBSE), molecularly imprinted polymers (MIPs), high-capacity sorbent extraction (HCSE), and needle-trap devices (NTD), are outlined. Additionally, novel forms of sorbent-based extraction methods such as thin-film solid-phase microextraction (TF-SPME) are presented. The utility and challenges related to these techniques are discussed in this review. Finally, the directions and need for future studies are addressed.

Headspace stir-bar sorptive extraction combined with gas chromatography-mass spectrometry for trace analysis of volatile organic compounds in Schisandra chinensis Baillon (omija)

Analyzing volatile organic compounds (VOCs) in food is crucial but challenging. Schisandra chinensis Baillon (omija) is an herbal plant with various functional health activities. Previous VOC analyses focused on S. chinensis fruit but not its leaves. Therefore, VOCs in S. chinensis fruit and leaves were analyzed using headspace stir-bar sorptive extraction (HS-SBSE)-GC-MS, and optimal conditions were established. Various factors, such as the sample preparation method, twister stir-bar type, sample amount, extraction temperature, and extraction time, expected to affect extraction were carefully optimized. Under the optimal conditions, 35 and 40 VOCs were identified in S. chinensis fruit and leaves, respectively. This HS-SBSE method is capable of rapid analysis and a low contamination rate without requiring organic solvents. These findings provide practical guidelines for HS-SBSE applications in various food matrices by providing analytical methods for VOC detection.

Characterization of Aroma Active Compound Production during Kombucha Fermentation: Towards the Control of Sensory Profiles

Since the sensorial profile is the cornerstone for the development of kombucha as a beverage with mass market appeal, advanced analytical tools are needed to gain a better understanding of the kinetics of aromatic compounds during the fermentation process to control the sensory profiles of the drink. The kinetics of volatile organic compounds (VOCs) was determined using stir bar sorptive extraction-gas chromatography-mass spectrometry, and odor-active compounds were considered to estimate consumer perception. A total of 87 VOCs were detected in kombucha during the fermentation stages. The synthesis of mainly phenethyl alcohol and isoamyl alcohol probably by Saccharomyces genus led to ester formation. Moreover, the terpene synthesis occurring at the beginning of fermentation (Δ-3-carene, α-phellandrene, γ-terpinene, m- and p-cymene) could be related to yeast activity as well. Principal component analysis identified classes that allowed the major variability explanation, which are carboxylic acids, alcohols, and terpenes. The aromatic analysis accounted for 17 aroma-active compounds. These changes in the evolution of VOCs led to flavor variations: from citrus-floral-sweet notes (geraniol and linalool domination), and fermentation brought intense citrus-herbal-lavender-bergamot notes (α-farnesene). Finally, sweet-floral-bready-honey notes dominated the kombucha flavor (2-phenylethanol). As this study allowed to estimate kombucha sensory profiles, an insight for the development of new drinks by controlling the fermentation process was suggested. Such a methodology should allow a better control and optimization of their sensory profile, which could in turn lead to greater consumer acceptance.

Occurrence, transport and environmental risk assessment of pharmaceuticals and personal care products (PPCPs) at the mouth of Jiaozhou Bay, China based on stir bar sorptive extraction

In recent years, research on pharmaceuticals and personal care products (PPCPs) in the marine environment has attracted increasing attention worldwide. However, more work is needed to improve PPCPs detection methods, specifically for seawater environments. An analytical method based on stir bar sorptive extraction (SBSE) had been developed and fully optimized for the pretreatment and detection of ten widely used PPCPs that are commonly found in seawater samples. By optimizing several variables including the material of the stir bars, extraction temperature, extraction time, ionic strength, desorption solvent, and desorption time, the optimized method has achieved excellent results in the detection and quantification of target PPCPs with detection limits ranging from 0.03 to 1 ng/L. The distribution of target PPCPs at the mouth of Jiaozhou Bay was successfully determined by this method, and the concentrations and detection frequencies of PPCPs varied greatly from N.D. to 449.36 ng/L and from 9.1 % to 100 %, respectively. Moreover, the distributions of PPCPs were explained by the Lagrangian particle-tracking model, and the results showed that the Tuandao sewage treatment plant had the most significant impact on the study area. The environmental risk assessment results showed that several target PPCPs might pose risks to aquatic organisms. In particular, triclocarban should receive more attention and the risk quotients of the mixtures (MRQ) should not be ignored.

Fluorine-Functionalized Covalent-Organic-Framework-Coated Stir Bar for the Extraction of Benzoylurea Insecticides in Pear Juice and Beverage Followed by High-Performance Liquid Chromatography-Ultraviolet Detection

A fluorinated covalent organic framework (COF), named F-COF, was fabricated via simple room-temperature synthesis. With the characteristics of rich fluorine atoms, hydrophobicity, and large conjugated structure, F-COF was evaluated for the extraction of five benzoylurea insecticides (BUs) containing fluorine atoms, benzene ring, and urea bridge. Specifically, F-COF-coated stir bars were prepared by physical adhesion and exhibited higher extraction recovery (73-93 versus 40-85%) toward BUs than commercial stir bars in a shorter extraction time (50 min versus 24 h). The adsorption behavior of BUs on F-COF was explored, and it was assumed that the halogen bond (O-F), hydrophobic interaction, electrostatic interaction, and π-π stacking contributed to the adsorption. On the basis of it, a method combining stir bar sorptive extraction with liquid chromatography-ultraviolet detector was developed for trace analysis of five BUs. Under the optimal conditions, the limits of detection for BUs were found to be 0.301-0.672 μg/L, with the linear range of 1.0/2.0-500 μg/L and relative standard deviations of <8.0% (c = 5 μg/L and n = 7). The accuracy of the proposed method was validated by the recovery test, and the recoveries of target BUs in spiked pear juice and pear beverage were 82.0-113 and 84.0-112%, respectively.

Free versus droplet-bound aroma compounds in sparkling beverages

The initial experience of a beverage's flavor after opening the bottle is created by a combination of the gas phase and droplet-bound odorants. However, most studies do not consider this combination, and focus on the odor-active components in the liquid or gas phase, separately. To cover this aspect, a filter from pyrolyzed polyacrylonitrile fiber was packed inside thermal desorption unit liner and used for trapping droplet-bound odorants. Additionally, polydimethylsiloxane coated thin-film was applied for extraction of gas-phase aroma. Following trapping/extraction, the devices were desorbed and compounds were separated using GC-MS. The odorants in commercial sparkling beverages were quantified immediately after opening the bottle to mimic real-life conditions of the consumer's experience of the flavor. The reported results provide a more comprehensive understanding of flavor perception in effervescent drinks by considering both gas and droplet phase.

Development of hybrid monoliths incorporating metal–organic frameworks for stir bar sorptive extraction coupled with liquid chromatography for determination of estrogen endocrine disruptors in water and human urine samples

A novel coating based on hybrid monolith with metal–organic framework (MOF) onto conventional Teflon-coated magnetic stir bars was developed. For this purpose, the external surface of the Teflon stir bar was firstly vinylized in order to immobilize a glycidyl methacrylate (GMA)–based polymer onto the magnet. Then, an amino-modified MOF of type MIL-101 (NH₂-MIL-101(Al)) was covalently attached to the GMA-based monolith. After the synthesis process, several parameters affecting extraction of target estrogens by stir bar sorptive extraction (SBSE) including pH, ionic strength, extraction time, stirring rate, desorption solvent, and desorption time were also investigated. The resulting hybrid monolith was evaluated as SBSE sorbent for extraction of three estrogens (estrone, 17β-estradiol, estriol) and synthetic 17β-ethinylestradiol from water and human urine samples followed by HPLC with fluorescence detection (excitation and emission wavelengths, 280 and 310 nm, respectively). Under the optimal experimental conditions, the analytical figures of the method were established, achieving satisfactory limits of detection in the range of 0.015–0.58 µg L⁻¹, recovery results ranging from 70 to 95% with RSD less than 6%, and precision values (intra- and inter-extraction units) below 6%.

Solventless Microextration Techniques for Pharmaceutical Analysis: The Greener Solution

Extensive efforts have been made in the last decades to simplify the holistic sample preparation process. The idea of maximizing the extraction efficiency along with the reduction of extraction time, minimization/elimination of hazardous solvents, and miniaturization of the extraction device, eliminating sample pre- and posttreatment steps and reducing the sample volume requirement is always the goal for an analyst as it ensures the method’s congruency with the green analytical chemistry (GAC) principles and steps toward sustainability. In this context, the microextraction techniques such as solid-phase microextraction (SPME), stir bar sorptive extraction (SBSE), microextraction by packed sorbent (MEPS), fabric phase sorptive extraction (FPSE), in-tube extraction dynamic headspace (ITEX-DHS), and PAL SPME Arrow are being very active areas of research. To help transition into wider applications, the new solventless microextraction techniques have to be commercialized, automated, and validated, and their operating principles to be anchored to theory. In this work, the benefits and drawbacks of the advanced microextraction techniques will be discussed and compared, together with their applicability to the analysis of pharmaceuticals in different matrices.

Characterisation of the volatile compounds profile of Chinese pan-fried green tea in comparison with baked green tea, steamed green tea, and sun-dried green tea using approaches of molecular sensory science

Pan-fried green tea (PGT) is an easily acceptable tea drink for general consumers. In this study, volatile profiles and characteristic aroma of 22 representative Chinese PGT samples were extracted using stir bar sorptive extraction (SBSE) and analysed by gas chromatography-mass spectrometry (GC-MS), gas chromatography-olfactometry (GC-O) analysis, and odour activity value (OAV) calculations. In total, 88 volatile compounds were identified. Alcohols (45%), esters (19%), and ketones (16%) were the dominant volatiles, and geraniol (484.8 μg/kg) was the most abundant volatile component in PGT, followed by trans-β-ionone and linalool. In addition, the differences of aroma characteristics among PGT and other three types of green tea, namely baked green tea, steamed green tea, and sun-dried green tea, were also observed using partial least squares discriminant analysis (PLS-DA) and heatmap analysis, and it was found that β-myrcene, methyl salicylate, (E)-nerolidol, geraniol, methyl jasmonate were generally present at higher content in PGT. This is the first comprehensive report describing the volatile profiles of Chinese PGT, and the findings from this study can advance our understanding of PGT aroma quality, and provide important theoretical basis for processing and quality control of green tea products.

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Volatiles of pan-fried green teas were extracted using stir bar sorptive extraction.

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Pan-fried green tea was rich in alcohols, esters, and ketones.

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Trans-β-ionone has both the highest odour activity value and aroma intensity.

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Sixteen key aroma compounds were identified by means of molecular sensory science.

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The differences of volatiles among four types of green teas were revealed.

The quality of composts prepared in automatic composters from fruit waste generated by the production of beverages

Ensuring the processing of food waste from the production of food and beverages intheautomatic composters can be difficult because of the physicochemical properties of input raw materials. Very often, the final product does not meet the requirements forcomposts according to the European Compost Network. Optimisation of input food waste from theproduction ofbeverages was performed by the addition of the bulk materials such assawdust and clay minerals (bentonite). Toxicity of the compost is caused by organic compounds with polar and non-polar properties. These compounds belong to the groups ofalcohols, aldehydes and ketones, carboxylic acids, tannin, and phenols, coumarins and terpenes. Phytotoxicity is mostly influenced by the group of terpenes. The addition ofsawdust used as bulking agent decreases the concentrations of almost all chemical compounds. Thegroup of tannin and compounds containing phenols represents an exception because these compounds are released from sawdust.

Determination of Droplet-Bound and Free Gas-Phase Fragrances Using a Filter-Incorporated Needle-Trap Device and Solid-Phase Microextraction Technologies

Some of the fragrance compounds in aerosols tend to remain trapped inside the droplets. The ability to capture these droplets would make it possible to desorb and transfer the analytes dissolved within for determination. In this study, we design a novel filter-incorporated needle-trap device and use it to capture fragrance compounds in droplets as well as the gas phase of seven aerosol spray samples. For comparison, thin-film and solid-phase microextraction were also employed to extract gas-phase-borne fragrances from the same sprays. The results revealed that the filter-incorporated needle-trap device enables the extraction of total concentrations due to its ability to trap fragrance-containing droplets, whereas thin-film and solid-phase microextraction are only able to extract unbound compounds present in the gas phase. In addition, the developed needle-trap device provided acceptable results, proving its applicability for the analysis of aroma in other samples, such as beer and soda.

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.

Aroma and catechin profile and in vitro antioxidant activity of green tea infusion as affected by submerged fermentation with Wolfiporia cocos (Fu Ling)

In response to the increasing interest of western consumers in high antioxidant activity of green tea but their low acceptance of its green odor, we employed a new starter culture, Wolfiporia cocos to tune flavor of green tea infusion. After submerged fermentation for 17 h, W. cocos changed the characteristic green odor to an attractive floral, jasmine-like, and slightly citrus-like flavor while preserving most of in vitro antioxidant activity. By application of mSBSE-GC-MS-O combined with sensorial tests, the formed pleasant aroma was mainly attributed to methyl anthranilate (OAV 802), linalool (OAV 190), 2-phenylethanol (OAV165), and geraniol (OAV 118). Concurrently, the catechin profile determined by UHPLC-MS showed diverse reduction rates (10-50%) for the individual catechins after fermentation. Nevertheless, up to 80% of in vitro antioxidant activity in DPPH assay was preserved. Overall, our findings provide an innovative approach to naturally flavor green tea while retaining the antioxidant activity.

Hydrophilic carboxyl supported immobilization of UiO-66 for novel bar sorptive extraction of non-steroidal anti-inflammatory drugs in food samples

Herein, the preparation of UiO-66 on frosted glass rod (FGR) was proposed through the coordination interaction of Zr-OH groups and carboxyl sites on FGR. The relative standard deviations (RSDs) of intra-batch and inter-batch were below 8.0% (n = 7). UiO-66-modified FGR (UiO-66@FGR) was applied to the extraction and monitoring of five non-steroidal anti-inflammatory drugs (NSAIDs) by coupling to novel bar sorptive extraction (BSE) with ultra-high performance liquid chromatography (UPLC). Sample volume, stirring rate, extraction time, sample pH value, desorption solvent, and desorption time were investigated. NSAIDs (ketoprofen, flurbiprofen, ibuprofen, naproxen, and diclofenac sodium) were determined at a low limit of detection (0.92 ng/mL) over a wide linear range (10-1500 ng/mL). The developed method was used to analyze NSAIDs in sheep muscle, chicken wing, and milk with recoveries of 80.8%-117.2%, RSDs < 6.5%. Fabricated UiO-66@FGR exhibited excellent reproducibility, stability, and good adsorption property towards NSAIDs in food samples.

Insight into the volatile profiles of four types of dark teas obtained from the same dark raw tea material

Various dark teas are quite different in their volatile profiles, mainly due to the huge differences in the phytochemical profiles of dark raw tea and the diverse post-fermentation processing technologies. In this study, gas chromatography-mass spectrometry (GC-MS), qualitative GC-olfactometry (GC-O), and enantioselective GC-MS coupled with multivariate analysis were applied to characterise the volatile profiles of various dark teas obtained from the same dark raw tea material. A total of 159 volatile compounds were identified by stir bar sorptive extraction (SBSE) combined with GC-MS, and 49 odour-active compounds were identified. Moreover, microbial fermentation could greatly influence the distribution of volatile enantiomers in tea, and six pairs of enantiomers showed great diversity of enantiomeric ratios among various dark teas. These results suggest that post-fermentation processing technologies significantly affect the volatile profiles of various dark teas and provide a theoretical basis for the processing and quality control of dark tea products.

Comprehensive Evaluation of Stable Neuronal Cell Adhesion and Culture on One-Step Modified Polydimethylsiloxane Using Functionalized Pluronic

Polydimethylsiloxane (PDMS) is a popular and property-advantageous material for developing biomedical microsystems and advancing cell microengineering. The requirement of constructing a robust cell-adhesive PDMS interface drives the exploration of simple, straightforward, and applicable surface modification methods. Here, a comprehensive evaluation of highly stable neuronal cell adhesion and culture on the PDMS surface modified in one step using functionalized Pluronic is presented. According to multiple comparative tests, this modification is sufficiently verified to enable more significant cell adhesion and spreading in both quantity and stability, higher neuronal differentiation and viability/growth, more complete formation of the neuronal network, and stabler neuronal cell culture than the common coating tools on the PDMS substrate. The comparable and even superior cellular effects of this modification on PDMS to the standard coating of polystyrene for in vitro neurological research are demonstrated. Long-term microfluidic neuron culture with stable adhesion and high differentiation on the modified PDMS interface is accomplished, too. The achievement provides a detailed experimental demonstration of this simple and effective modification for strengthening neuronal cell culture on the PDMS substrate, which is useful for potential applications in the fields of neurobiology, neuron microengineering, and brain-on-a-chip.

Miniaturized analytical methods for determination of environmental contaminants of emerging concern - A review

The determination of contaminants of emerging concern (CECs) in environmental samples has become a challenging and critical issue. The present work focuses on miniaturized analytical strategies reported in the literature for the determination of CECs. The first part of the review provides brief overview of CECs whose monitoring in environmental samples is of particular significance, namely personal care products, pharmaceuticals, endocrine disruptors, UV-filters, newly registered pesticides, illicit drugs, disinfection by-products, surfactants, high technology rare earth elements, and engineered nanomaterials. Besides, an overview of downsized sample preparation approaches reported in the literature for the determination of CECs in environmental samples is provided. Particularly, analytical methodologies involving microextraction approaches used for the enrichment of CECs are discussed. Both solid phase- and liquid phase-based microextraction techniques are highlighted devoting special attention to recently reported approaches. Special emphasis is placed on newly developed materials used for extraction purposes in microextraction techniques. In addition, recent contributions involving miniaturized analytical flow techniques for the determination of CECs are discussed. Besides, the strengths, weaknesses, opportunities and threats of point of need and portable devices have been identified and critically compared with chromatographic methods coupled to mass chromatography. Finally, challenging aspects regarding miniaturized analytical methods for determination of CECs are critically discussed.

Modern technologies for extraction of aroma compounds from fruit peels: a review

Fruit peel is an agricultural by-product and potential source to extract natural aroma compounds with low cost. In the past few decades, the extraction of plant aroma volatiles experienced a transition from traditional to modern technologies. This review summarizes the main aroma compounds in different fruit peels, evaluates modern extraction techniques applicable for these aroma compounds in terms of mechanism, procedure, merits and demerits, and practice. Additionally, the applications of fruit peel aroma extract in food, pharmaceutical and cosmetic industries are also discussed. This review provides comprehensive information for extraction and application of aroma compounds from fruit peels, which could facilitate the valorization of the agricultural by-products and reduce environmental impacts.

Chemical and Sensory Characteristics of Soy Sauce: A Review

Soy sauce is a fermented product, and its flavor is a complex mixture of individual senses which, in combination, create a strong palatable condiment for many Eastern and Western dishes. This Review focuses on our existing knowledge of the chemical compounds present in soy sauce and their potential relevance to the flavor profile. Taste is dominated by umami and salty sensations. Free amino acids, nucleotides, and small peptides are among the most important taste-active compounds. Aroma is characterized by caramel-like, floral, smoky, malty, and cooked potato-like odors. Aroma-active volatiles are chemically diverse including acids, alcohols, aldehydes, esters, furanones, pyrazines, and S-compounds. The origin of all compounds relates to both the raw ingredients and starter cultures used as well as the parameters applied during production. We are only just starting to help develop innovative studies where we can combine different analytical platforms and chemometric analysis to link flavor attributes to chemical composition.

Advancement in analytical techniques for the extraction of grape and wine volatile compounds

The grape and wine aroma is one of the most determining factors of quality, therefore the study of their volatile composition is a very important topic in vitiviniculture. The range of concentrations in which many of these compounds are found is quite low, in concentrations of ng/L; due to this, a sample preparation stage is necessary before doing the chromatographic analysis of the volatile compounds. In this review, the main analytical techniques used for the extraction of volatile compounds in grapes and wines are studied. The techniques presented are liquid-liquid extraction (LLE), solid phase extraction (SPE), solid phase microextraction (SPME), stir bar sorptive extraction (SBSE), and thin film solid phase microextraction (TF-SPME). For each of these techniques, a description was made, and the different characteristics were numbered, as well as their main advantages and disadvantages. Furthermore, from the second technique, a comparison is made with the previous techniques, explaining the reasons why new techniques have emerged. Throughout the review it is possible to see the different techniques that have been emerging in the past years as an improvement of the classical techniques.

Comparison of volatile trapping techniques for the comprehensive analysis of food flavourings by Gas Chromatography-Mass Spectrometry

Trapping volatiles is a convenient way to study aroma compounds but it is important to determine which volatile trapping method is most comprehensive in extracting the most relevant aroma components when investigating complex food products. Awareness of their limitations is also crucial. (Un)targeted metabolomic approaches were used to determine the volatile profiles of two commercial flavourings. Four trapping techniques were tested as was the addition of salt to the mixture. Comprehensiveness and repeatability were compared and SBSE proved particularly suitable for extracting components such as polysulfides, pyrazines and terpene alcohols, and provided an overall broader chemical spectrum. SPME proved to be more suitable in extracting sesquiterpenes and DHS in extracting monoterpenes. Adding salt to the sample had only quantitative effects on volatiles as detected by SPME. These results help clarify the advantages and limitations of different trapping techniques and hence deliver a valuable decision tool for food matrix analysis.

The retrograde adsorption phenomenon at the onset of breakthrough and its quantitation: An experimental case study for gaseous toluene on activated carbon surface

The adsorption dynamics of common solid sorbents against various pollutant species are yet poorly understood with respect to the retrograde phenomenon in which the relationship between breakthrough vs. pulled volume is characterized by an early unusual trend (initial increase followed by a decrease to a minimum) and by a normal trend of finally increasing to 100% (or equilibrium). If such trend is expressed in terms of the partition coefficient (PC), a reversed trend of adsorption processes becomes more evident. Retrograde has been previously observed in the initial breakthrough (<10%) isotherms in continuous flow gas-phase adsorption processes. However, retrograde has been neglected/overlooked and not discussed at all in the main stream literature even when it is explicitly observed from isotherm datasets. To properly describe the various aspects of such process, a stop-flow technique was developed to measure the adsorption isotherm of a model volatile organic compound (i.e., toluene in this study) onto a commercial low-cost sorbent (activated carbon: AC). Accordingly, a 10% breakthrough volume of 762 L atm g^-1 (corresponding adsorption capacity of 142 mg g^-1) was determined (at an inlet stream 5 Pa of toluene in 1 atm of N₂ and 5 mg of AC). This automated method was effective to generate a detailed breakthrough profile at high stream-flow rates (or high space velocities) to specifically detect the retrograde phenomenon at the breakthrough onset. This study offers a practical approach towards establishing an in-depth monitoring protocol for the rare retrograde phenomenon.

Novel sample preparation approaches in gas chromatographic analysis: Promising ideas

The development of sample preparation procedures is still a dynamic process despite a number of already proposed techniques. The main challenge in this research field is to fully replace classical procedures like liquid-liquid extraction and solid-phase extraction in gas chromatographic analysis. Some progress has been already achieved for the last 20 years when miniaturized techniques were incorporated in ISO standards. The current review is focused on novel approaches in sample treatment that appeared since 2010. It includes research studies describing non-conventional instrumental design available to inspire future progress in the field. A combination of a few extraction principles and supporting with additional treatment are the main core suggested for improvement of sample preparation efficiency. This requires good compatibility of extraction media, assessment of multiple experimental parameters, and potential automatization possibilities.

Development of an in-mouth headspace sorptive extraction method (HSSE) for oral aroma monitoring and application to wines of different chemical composition

An in-mouth headspace sorptive extraction (HSSE) procedure for the in-mouth volatile sampling of wine aroma compounds during wine tasting has been developed. The procedure is based on the application of a PDMS (polydimethylsiloxane) twister contained inside a tailored made glass tube placed into the headspace of the mouth after rinsing and spitting-off the wine, which is then followed by gas chromatography mass spectrometry analysis (GCMS). Various parameters that might affect the performance of the method (extraction time, aroma concentration) were firstly investigated. Despite the short selected in-mouth extraction time (30 s); the application of the in-mouth HSSE procedure using real wines allowed the detection of >30 volatile compounds from different chemical families in the oral cavity in a single run, and which are also present in the wine at very low concentrations. Additionally, the in-mouth HSSE profile allowed us to distinguish between wines types (with different non-volatile and volatile composition) in a similar way to that when using data from the headspace of the wine (wine-HSSE-GCMS). The simplicity, sensitivity, good repeatability and the easy automatization of this procedure, makes this technique a reliable and feasible tool to determine the chemical and biochemical changes of these compounds in the mouth in real physiological conditions providing useful -in vivo analytical data to better correlate with sensory studies.

Current Trends in Fully Automated On-Line Analytical Techniques for Beverage Analysis

The determination of target analytes in complex matrices such as beverages requires a series of analytical steps to obtain a reliable analysis. This critical review presents the current trends in sample preparation techniques based on solid phase extraction miniaturization, automation and on-line coupling. Techniques discussed include solid-phase extraction (SPE), solid-phase microextraction (SPME), in-tube solid-phase microextraction (in-tube SPME) and turbulent-flow chromatography (TFC). Advantages and limitations, as well as several of their main applications in beverage samples are discussed. Finally, fully automated on-line systems that involve extraction, chromatographic separation, and tandem mass spectrometry in one-step are introduced and critically reviewed.