Automated determination of phenolic compounds in wine, berry, and grape samples using 96-blade solid phase microextraction system coupled with liquid chromatography-tandem mass spectrometry

Current analytical strategies for the determination of resveratrol in foods

Resveratrol, a non-flavonoid polyphenolic compound, possesses various beneficial properties such as anti-cancer, anti-aging, anti-bacterial, and antioxidant effects. It is naturally produced by many plants in response to stimulation. However, the content of resveratrol in natural plants can vary significantly, ranging from micrograms to milligrams per kilogram. As the demand for resveratrol increases, the development of methods for extracting and quantifying resveratrol in food has become a rapidly growing field in recent years. This review aims to comprehensively summarize the progress made in resveratrol analysis in food over the past decade (2012-2022), with a specific focus on the latest advancements in extraction and detection technologies. The objective is to offer a valuable reference for further research and utilization of resveratrol in various food applications.

Determination of hormones in urine by hollow fiber microporous membrane liquid-liquid extraction associated with 96-well plate system and HPLC-FLD detection

In this work, hollow-fiber microporous membrane liquid-liquid extraction (HF-MMLLE) was associated with a 96-well plate system for the determination of estrone, 17-β-estradiol, estriol and 17-α-ethinylestradiol in urine samples. This method exhibited some advantages, such as low cost, easy application, high-throughput and environmentally-friendly aspects. The type of organic solvent to fill the membrane, ionic strength effect, sample dilution, extraction and desorption time, and desorption solvent were examined. After the optimizations, the conditions were comprised of 45 min of extraction, 1-octanol as organic solvent and 15% (w/v) of NaCl; methanol was used as desorption solvent, and the desorption time was fixed at 10 min. The dilution of the sample increased the sensitivity due to the reduction of matrix effects; thus, urine samples were diluted 40-fold. The limits of detection ranged from 0.03 μg L^-1 for 17-β-estradiol to 15 μg L^-1 for estrone, and the limits of quantification ranged from 0.1 μg L^-1 for 17-β-estradiol to 10 μg L^-1 for estrone. The intra-day precision varied from 1.0% for estriol to 13.3% for 17-α-ethinylestradiol, and inter-day precision varied from 7.3% for estrone to 18.1% for estriol. The relative recoveries varied from 82 to 118%.

The Potential of Microextraction Techniques for the Analysis of Bioactive Compounds in Food

For a long time, the importance of sample preparation and extraction in the analytical performance of the most diverse methodologies have been neglected. Cumbersome techniques, involving high sample and solvent volumes have been gradually miniaturized from solid-phase and liquid-liquid extractions formats and microextractions approaches are becoming the standard in different fields of research. In this context, this review is devoted to the analysis of bioactive compounds in foods using different microextraction approaches reported in the literature since 2015. But microextraction also represents an opportunity to mitigate the environmental impact of organic solvents usage, as well as lab equipment. For this reason, in the recent literature, phenolics and alkaloids extraction from fruits, medicinal herbs, juices, and coffee using different miniaturized formats of solid-phase extraction and liquid-liquid microextraction are the most popular applications. However, more ambitious analytical limits are continuously being reported and emergent sorbents based on carbon nanotubes and magnetic nanoparticles will certainly contribute to this trend. Additionally, ionic liquids and deep eutectic solvents constitute already the most recent forefront of innovation, substituting organic solvents and further improving the current microextraction approaches.

Benefits of Innovative and Fully Water-Compatible Stationary Phases of Thin-Film Microextraction (TFME) Blades

Octadecyl (C₁₈) groups are arguably the most popular ligands used for preparation of solid phase microextraction (SPME) devices. However, conventional C₁₈-bonded silica particles are not fully compatible with the nearly 100% aqueous composition of typical biological samples (e.g., plasma, saliva, or urine). This study presents the first evaluation of thin-film SPME devices coated with special water-compatible C₁₈-bonded particles. Device performance was assessed by extracting a mixture of 30 model compounds that exhibited various chemical structures and properties, such as hydrophobicity. Additionally, nine unique compositions of desorption solvents were tested. Thin-film SPME devices coated with C₁₈-bonded silica particles with polar end-capping groups (10 µm) were compared with conventional trimethylsilane end-capped C₁₈-bonded silica particles of various sizes (5, 10, and 45 µm) and characteristics. Polar end-capped particles provided the best extraction efficacy and were characterized by the strongest correlations between the efficacy of the extraction process and the hydrophobicity of the analytes. The results suggest that the original features of octadecyl ligands are best preserved in aqueous conditions by polar end-capped particles, unlike with conventional trimethylsilane end-capped particles that are currently used to prepare SPME devices. The benefits associated with this improved type of coating encourage further implementation of microextractraction as greener alternative to the traditional sample preparation methods.

Food Bioactive Compounds and Emerging Techniques for Their Extraction: Polyphenols as a Case Study

Experimental studies have provided convincing evidence that food bioactive compounds (FBCs) have a positive biological impact on human health, exerting protective effects against non-communicable diseases (NCD) including cancer and cardiovascular (CVDs), metabolic, and neurodegenerative disorders (NDDs). These benefits have been associated with the presence of secondary metabolites, namely polyphenols, glucosinolates, carotenoids, terpenoids, alkaloids, saponins, vitamins, and fibres, among others, derived from their antioxidant, antiatherogenic, anti-inflammatory, antimicrobial, antithrombotic, cardioprotective, and vasodilator properties. Polyphenols as one of the most abundant classes of bioactive compounds present in plant-based foods emerge as a promising approach for the development of efficacious preventive agents against NCDs with reduced side effects. The aim of this review is to present comprehensive and deep insights into the potential of polyphenols, from their chemical structure classification and biosynthesis to preventive effects on NCDs, namely cancer, CVDs, and NDDS. The challenge of polyphenols bioavailability and bioaccessibility will be explored in addition to useful industrial and environmental applications. Advanced and emerging extraction techniques will be highlighted and the high-resolution analytical techniques used for FBCs characterization, identification, and quantification will be considered.

Fabrication of montmorillonite/ionic liquid composite coated solid-phase microextraction fibers for determination of phenolic compounds in fruit juices by gas chromatography and liquid chromatography

Novel montmorillonite composites including ionic liquid were prepared and utilized as coating materials for solid phase microextraction fibers. Ionic liquids containing amino terminated imidazolium cations with methyl and benzyl groups and hydrophobic anions (bis(trifluoromethylsulfonyl)imide) and hydrophilic anions (bromide and tetrafluoroborate) were intercalated to KSF-montmorillonite using stainless steel wire as support by using the layer-by-layer technique. After optimization of experimental conditions, solid phase microextraction (SPME) coupled to gas chromatography/mass spectrometry (SPME-GC/MS) after derivatization by silylation and high performance liquid chromatography/diode array detector (SPME-HPLC/DAD) were developed for the determination of 16 phenolic compounds. The developed SPME-GC/MS method had wider linearity and lower limit of detection than the developed SPME-HPLC/DAD method with similar repeatability (for 5 runs, less than 4.2 %) for a single fiber. The percentage of the variance between two different fibers was less than 6.0 % in both methods. The developed SPME methods were applied successfully to fresh fruit juices and the relative recoveries and the repeatabilities from spiked fruit juice samples were satisfactorily achieved. The results obtained with both chromatographic methods were in good agreement with each other.

Systematic Evaluation of Different Coating Chemistries Used in Thin-Film Microextraction

A systematic evaluation of eight different coatings made of solid phase extraction (SPE) and carbon-based sorbents immobilized with polyacrylonitrile in the thin-film microextraction (TFME) format using LC-MS/MS was described. The investigated coatings included graphene, graphene oxide, multi-walled carbon nanotubes (MWCNTs), carboxylated MWCNTs, as carbon-based coatings, and polystyrene-divinylbenzene (PS-DVB), octadecyl-silica particles (C18), hydrophilic-hydrophobic balance particles (HLB) and phenyl-boronic acid modified particles (PBA), as SPE-based coatings. A total of 24 compounds of diverse moieties and of a wide range of polarities (log P from -2.99 to 6.98) were selected as probes. The investigated coatings were characterized based on their extraction performance toward the selected probes at different pH values and at optimized desorption conditions. In the case of SPE-based coatings, PS-DVB and HLB exhibited a balanced extraction for compounds within a wide range of polarities, and C18 showed superior extraction recoveries for non-polar analytes. Carbon-based coatings showed high affinity for non-polar compounds given that their main driving force for extraction is hydrophobic interactions. Interestingly, among the studied carbon-based coatings, graphene oxide showed the best extraction capabilities toward polar compounds owing to its oxygen-containing groups. Overall, this work provided important insights about the extraction mechanisms and properties of the investigated coatings, facilitating the coating selection when developing new TFME applications.

Introducing a mechanically robust SPME sampler for the on-site sampling and extraction of a wide range of untargeted pollutants in environmental waters

The present study introduces a mechanically robust, sealable SPME sampler for the on-site sampling and extraction of a wide range of untargeted pollutants in environmental waters. Spray-coating and dip coating methodologies were used to coat the surfaces of six stainless steel bolts with a layer of HLB/PAN particles, which served as the extractive substrate in the proposed device. In addition, this sampler was designed to withstand rough handling, long storage times, and various environmental conditions. In order to identify whether the sampler was able to stabilize extracted compounds for long periods of time, the effects of storage time and temperature were evaluated. The results of these tests showed no significant differences in the quantity and quality of the extracted chemicals following 12 days storage at room temperature, thus confirming the device's suitability for use at sampling sites that are far away from the laboratory facilities. The proposed device was also used to perform extraction and untargeted analyses of river waters in five different geographical locations. The constituent chemicals in the samplers were analyzed and determined using high-resolution HPLC-Orbitrap MS. Toxin and Toxin-Target Database was used as a reference database for toxins and environmental contaminants. Ultimately, over 80 tentative chemicals with widely varying hydrophobicities ranging within -2.43 < logP <11.9-including drugs, metabolites, wide ranges of toxins, pesticide, and insecticides-were identified in the samplers used in the different rivers. The log P values for the tentative analytes confirmed that the introduced device is suitable for the extraction and trace analysis of wide ranges of targeted and untargeted pollutants.

High-Throughput Solid-Phase Microextraction-Liquid Chromatography-Mass Spectrometry for Microbial Untargeted Metabolomics

Nowadays, metabolomics data, when combined with other "omics" data, can provide important information regarding systems biology. Acquiring a comprehensive untargeted metabolome snapshot of complex sample matrices requires proper sample preparation, and access to sophisticated analytical instrumentation such as mass spectrometry. In metabolomics, sample preparation has substantial influence on the quality of the obtained metabolome profile. To achieve a real snapshot of the metabolome, the analysis method must be capable of inhibiting metabolite interconversion by immediately quenching all metabolome activity. Application of solid-phase microextraction (SPME), particularly in its in vivo set up, when undertaken in conjunction with a conscious selection of coating type based on the chosen sample matrix and the physicochemical properties of the analytes under study, is capable of providing extraction of representative metabolomes for many biological matrices. Metabolomes identified by SPME include low-abundance species and short-lived or unstable metabolites hardly captured by traditional extraction techniques. SPME coupled to liquid chromatography-high-resolution mass spectrometry has recently been introduced as an innovative alternative technique that integrates sampling, sample preparation, and extraction for metabolic profiling and isolation of candidate biomarkers. This chapter presents a detailed protocol for microbial metabolome analysis of Escherichia coli as a model organism, applying the high-throughput SPME-LC-MS workflow.

Hollow-fiber renewal liquid membrane extraction coupled with 96-well plate system as innovative high-throughput configuration for the determination of endocrine disrupting compounds by high-performance liquid chromatography-fluorescence and diode array detection

This paper describes a new configuration of the hollow fiber renewal liquid membrane (HFRLM) procedure for the high-throughput determination of the endocrine disrupting compounds 4-nonylphenol, 4-octylphenol, 4-tert-octylphenol, methylparaben, ethylparaben and bisphenol A using a 96-well plate system and high-performance liquid chromatography. In this configuration, cylindrical blades were adapted as a support for polypropylene membranes used as supported liquid membranes in the HFRLM approach. The proposed configuration exhibited important advantages including high-throughput, low solvent and sample consumption, and good analytical performance. The optimized extraction conditions were achieved with the use of a mixture comprised of 50:50 v/v 1-octanol:hexane as the supported liquid membrane, sample pH 5, extraction solvent 15 μL (hexane) and extraction time 45 min. The limits of quantification varied from 0.5 μg L^-1 for 4-octylphenol to 15 μg L^-1 for methylparaben and ethylparaben and the r² ranged from 0.9908 for methylparaben to 0.9992 for 4-tert-octylphenol. HFRLM combined with the use of a 96-well plate provides an environmentally-friendly configuration. It offers good accuracy when applied to analyze water samples, with relative recoveries ranging from 72 to 130%, for 4-octylphenol and 4-nonylphenol, respectively, and precision varying from 1 to 14.3%, for 4-nonylphenol at 1.0 μg L^-1 and bisphenol A at 8.0 μg L^-1, respectively.

Development and Validation of a High-performance Liquid Chromatography-Diode-array Detection Method for the Determination of Eight Phenolic Constituents in Extracts of Different Wine Species

Objectives

A new HPLC method was developed and validated for the determination of some phenolic compounds; gallic acid, chlorogenic acid, epigallocatechin, caffeic acid, vanillin, p-coumaric acid, rutin, and quercetin in some local wine and fruit wine samples.

Materials and Methods

Analyses were performed on a Zorbax Eclipse C18 column (4.6 x 150 mm, 3.5-µm particle size) using a gradient system. Mobile phase A was a 10-mM phosphoric acid solution and mobile phase B was methanol using a flow rate of 1 mL/min. Phenolic components were monitored using a DAD at three different wavelengths.

Results

The developed and validated method was generally linear between the 1-100 ppm concentration range. Recovery values were obtained in the range of 95-105% and repetitive. The method was successfully applied to investigate the phenolic profiles of different wine samples.

Conclusion

As a result of the study, an accurate, sensitive and reliable HPLC-DAD method was developed. The method was successfully used to determine the concentrations of antioxidant phenolic constituents from some local wine extracts.

Simultaneous determination of quercetin and its metabolites in rat plasma by using ultra-high performance liquid chromatography tandem mass spectrometry

Fast, selective, and sensitive ultra-high performance liquid chromatography method with tandem mass spectrometry detection for the determination of quercetin and its metabolites with various physico-chemical properties such as molecular weight, lipophilicity, and acid-base properties has been developed. These compounds included small hydrophilic phenolic acids and more lipophilic metabolites with preserved flavonoid structure in small amount of rat plasma. The developed method enables selective separation of phenolic acids and a pair of isomers tamarixetin and isorhamnetin with satisfactory peak shapes and a high sensitivity using mass spectrometry detection. In addition, two sample preparation procedures including protein precipitation and microextraction in packed sorbent (MEPS) were optimized. The sample acidification included in protein precipitation as well as optimizing of MEPS sorbents and elution solvents improved isolation of quercetin and related compounds from rat plasma. Finally, both methods developed for sample preparation were fully validated to demonstrate sufficient accuracy and precision and acceptable matrix effects. Both sample preparation approaches combined with mass spectrometry-based quantification allowed the simultaneous determination of quercetin and its metabolites from a small amount of biological samples of only 50 μL. Due to the fast and non-selective parallel sample preparation, the protein precipitation was eventually applied to plasma samples derived from pharmacokinetic studies.

Trace-Level Volatile Quantitation by Direct Analysis in Real Time Mass Spectrometry following Headspace Extraction: Optimization and Validation in Grapes

Ambient ionization mass spectrometric (AI-MS) techniques like direct analysis in real time (DART) offer the potential for rapid quantitative analyses of trace volatiles in food matrices, but performance is generally limited by the lack of preconcentration and extraction steps. The sensitivity and selectivity of AI-MS approaches can be improved through solid-phase microextraction (SPME) with appropriate thin-film geometries, for example, solid-phase mesh-enhanced sorption from headspace (SPMESH). This work improves the SPMESH-DART-MS approach for use in food analyses and validates the approach for trace volatile analysis for two compounds in real samples (grape macerates). SPMESH units prepared with different sorbent coatings were evaluated for their ability to extract a range of odor-active volatiles, with poly(dimethylsiloxane)/divinylbenzene giving the most satisfactory results. In combination with high-resolution mass spectrometry (HRMS), detection limits for SPMESH-DART-MS under 4 ng/L in less than 30 s acquisition times could be achieved for some volatiles [3-isobutyl-2-methoxypyrazine (IBMP) and β-damascenone]. A comparison of SPMESH-DART-MS and SPME-GC-MS quantitation of linalool and IBMP demonstrates excellent agreement between the two methods for real grape samples (r² ≥ 0.90), although linalool measurements appeared to also include isobaric interference.

A novel molybdenum disulfide nanosheet self-assembled flower-like monolithic sorbent for solid-phase extraction with high efficiency and long service life

A novel material consisting of molybdenum disulfide (MoS₂) nanosheet that self-assemble into flower-like microspheres which aggregate to form a monolithic matrix with a micro or nano-scaled mesopore structure was successfully synthesized and used as an efficient sorbent for solid-phase extraction (SPE) due to its large specific adsorption area and good stability. The extraction properties of the as-prepared sorbent were evaluated by high-performance liquid chromatography with variable wavelength detection (HPLC-VWD) by analyzing four flavonoids (apigenin, quercetin, luteolin, and kaempferol). Under optimal conditions, the LODs and LOQs were found to be in the ranges of 0.1-0.25 and 0.4-0.5μgL^-1, respectively, and wide linear ranges were obtained with correlation coefficients (R) ranging from 0.9991 to 0.9996. Compared with commercial C18 and Alumina-N sorbents, the as-prepared sorbent showed high extraction efficiency at different concentrations of flavonoids. After 100 uses, the extraction ability of the self-assembled MoS₂ nanosheet monolithic sorbent had no evident decline, denoting a long service life. Finally, the SPE-HPLC-VWD method using the as-prepared sorbent was applied to flavonoid analysis in beverage samples with satisfactory results.

High throughput solid phase microextraction: A new alternative for analysis of cellular lipidome?

A new SPME method for untargeted lipidomic study of cell line cultures was proposed for the first time. In this study the feasibility to monitor changes in lipid profile after external stimuli was demonstrated and compared to the conventional Bligh & Dyer method. The human hepatocellular carcinoma (HCC) cell line was used as a model. The obtained results provided a list of up-regulated and down-regulated lipids through a comparison between control (non-stimulated) cells versus the group of cells treated with polyunsaturated fatty acid (20:5). Use of the SPME technique yielded a list of 77 lipid species whose concentrations were recognized to be significantly different between control and treated cells, from which 63 lipids were up-regulated in treated cells. In general, the list was comparable to the peer list obtained by the Bligh & Dyer method. However, more diversity of lipid classes and subclasses such as LPC, sphingomyelins, ceramides, and prenol lipids were observed with the application of the SPME method. Method precision for the SPME approach was within the acceptable analytical range (5-18% RSD) for all detected lipids, which was advantageous over solvent extraction applied. The evaluation of ionization efficiency indicated no matrix effect for the SPME technique, while Bligh & Dyer presented significant ionization suppression for low abundant species such as LysoPC, PG, ceramides, and sphingomyelins, and ionization enhancement for high abundant phospholipids such as PE.

Ultrafast Polyphenol Metabolomics of Red Wines Using MicroLC-MS/MS

The taste and quality of red wine are determined by its highly complex mixture of polyphenols and many other metabolites. No single method can fully cover the full metabolome, but even for polyphenols and related compounds, current methods proved inadequate. We optimized liquid chromatography resolution and sensitivity using 1 mm i.d. columns with microLC pumps and compared data-dependent to data-independent (SWATH) MS/MS acquisitions. A high-throughput microLC-MS method was developed with a 4 min gradient at 0.05 mL/min flow rate on a Kinetex C18 column and Sciex TripleTOF mass spectrometry. Using the novel software MS-DIAL, we structurally annotated 264 compounds including 165 polyphenols in six commercial red wines by accurate mass MS/MS matching. As proof of concept, multivariate statistics revealed the difference in the metabolite profiles of the six red wines, and regression analysis linked the polyphenol contents to the taste of the red wines.

In situ hydrothermal growth of a dual-ligand metal–organic framework film on a stainless steel fiber for solid-phase microextraction of polycyclic aromatic hydrocarbons in environmental water samples

In situ hydrothermal growth of bio-MOF-1 film on stainless steel fiber for solid-phase microextraction of polycyclic aromatic hydrocarbons.

The sensitive and selective adsorption of aromatic compounds with highly crosslinked polymer nanoparticles

This study presents the preparation and characterization of a nanoscale Davankov-type hyper-crosslinked-polymer (HCP) as an adsorbent of benzene-ring-containing dyes and organic pollutants. HCP nanoparticles post-crosslinked from a poly(DVB-co-VBC) precursor were synthesized in this study, possessing ultrahigh surface area, hydrophobicity and stability. The as-synthesized Davankov-type HCP exhibited a rapid and selective adsorption ability towards the benzene-ring-containing dyes due to its highly conjugated structure. Besides, for the first time, the prepared HCP nanoparticles were adopted for the adsorption of nonpolar organic pollutants by means of solid-phase microextraction (SPME). Owing to its high hydrophobicity, diverse pore size distribution and highly conjugated structure, a 10 μm HCP coating exhibited excellent adsorption abilities towards benzene-ring-containing polycyclic aromatic hydrocarbons (PAHs) and benzene series compounds (benzene, toluene, ethylbenzene and o-xylene; abbreviated to BTEX) and to highly hydrophobic long-chain n-alkanes. Finally, the HCP-nanoparticles-coated SPME fiber was applied to the simultaneous analysis of five PAHs in environmental water samples and satisfactory recoveries were achieved. The findings could provide a new benchmark for the exploitation of superb HCPs as effective adsorbents for SPME or other adsorption applications.

Bioanalytical method for in vitro metabolism study of repaglinide using 96-blade thin-film solid-phase microextraction and LC-MS/MS

BACKGROUND

A high-throughput bioanalytical method using 96-blade thin film microextraction (TFME) and LC-MS/MS for the analysis of repaglinide (RPG) and two of its main metabolites was developed and used for an in vitro metabolism study.

RESULTS

The target analytes were extracted from human microsomal medium by a 96-blade-TFME system employing the low-cost prototype 'SPME multi-sampler' using C18 coating. Method validation showed recoveries around 90% for all analytes and was linear over the concentration range of 2-1000 ng ml(-1) for RPG and of 2-500 ng ml(-1) for each RPG metabolite.

CONCLUSION

The method was applied to an in vitro metabolism study of RPG employing human liver microsomes and proved to be very useful for this purpose.

Development of high throughput 96-blade solid phase microextraction-liquid chromatrography-mass spectrometry protocol for metabolomics

In metabolomics, the workflow for quantitative and comprehensive metabolic mapping of cellular metabolites can be a very challenging undertaking. Sampling and sample preparation play a significant role in untargeted analysis, as they may affect the composition of the analyzed metabolome. In the current work, different solid phase microextraction (SPME) coating chemistries were developed and applied to provide simultaneous extraction of a wide range of both hydrophobic and hydrophilic cellular metabolites produced by a model organism, Escherichia coli. Three different LC-MS methods were also evaluated for analysis of extracted metabolites. Finally, over 200 cellular metabolites were separated and detected with widely varying hydrophobicities ranging within -7 < log P < 15, including amino acids, peptides, nucleotides, carbohydrates, polycarboxylic acids, vitamins, phosphorylated compounds, and lipids such as hydrophobic phospholipids, prenol lipids, and fatty acids at the stationary phase of the E. coli life cycle using the developed 96-blade SPME-LC-MS method.

Phenolic characterization and antimicrobial activity of folk medicinal plant extracts for their applications in olive production

Phytophthora spp is important in plant pathology due to the importance of the diseases it causes. In olive trees, severe damages are caused by the disease known as "dry branch" occasioned by Phytophthora nicotianae, P. citrophthora and P. palmivora. Much effort has been made to find efficient methods of control, with a low negative impact on environment. In this regard, treatment with plant extracts is a valid strategy. The aims of the present study are (i) to determine the polyphenol composition of extracts of Thymus vulgaris, Origanum vulgare, Matricaria recutita, and Larrea divaricata by CZE, (ii) correlate the analytical composition of these extracts with the inhibition on the mycelial growth, and (iii) determine the individual antimicrobial activity of the most active ingredients. A simple methodology was developed for the determination of catechin, naringenin, cinnamic acid, syringic acid, chlorogenic acid, apigenin, vanillic acid, luteolin, quercetin, and caffeic acid in plant extracts by CZE. The extraction of phenolic compounds in extract was performed by a miniaturized solid phase extraction using a home-made minicolumn packed with suitable filtering material (C18 , 50 mg). The optimized analyses conditions were: 30 mM boric acid buffer, pH 9.50; capillary, 57 cm full length, 50 cm effective length, 75 μm id, hydrodynamic injection 30 mbar, 2 s; 25 kV; 25°C, detection by UV absorbance at 290 nm. Sample results suggest that phenolic composition seems to have a great influence on inhibition of pathogens. The highest inhibitions of mycelial growth were observed for cinnamic acid and naringenin.

Nitro-substituted 3,3′-bis(indolyl)methane-modified silica gel as a sorbent for solid-phase extraction of flavonoids

An Nbim-modified silica sorbent was synthesized and characterized for extraction of flavonoids.

Sample preparation with solid phase microextraction and exhaustive extraction approaches: Comparison for challenging cases

In chemical analysis, sample preparation is frequently considered the bottleneck of the entire analytical method. The success of the final method strongly depends on understanding the entire process of analysis of a particular type of analyte in a sample, namely: the physicochemical properties of the analytes (solubility, volatility, polarity etc.), the environmental conditions, and the matrix components of the sample. Various sample preparation strategies have been developed based on exhaustive or non-exhaustive extraction of analytes from matrices. Undoubtedly, amongst all sample preparation approaches, liquid extraction, including liquid-liquid (LLE) and solid phase extraction (SPE), are the most well-known, widely used, and commonly accepted methods by many international organizations and accredited laboratories. Both methods are well documented and there are many well defined procedures, which make them, at first sight, the methods of choice. However, many challenging tasks, such as complex matrix applications, on-site and in vivo applications, and determination of matrix-bound and free concentrations of analytes, are not easily attainable with these classical approaches for sample preparation. In the last two decades, the introduction of solid phase microextraction (SPME) has brought significant progress in the sample preparation area by facilitating on-site and in vivo applications, time weighted average (TWA) and instantaneous concentration determinations. Recently introduced matrix compatible coatings for SPME facilitate direct extraction from complex matrices and fill the gap in direct sampling from challenging matrices. Following introduction of SPME, numerous other microextraction approaches evolved to address limitations of the above mentioned techniques. There is not a single method that can be considered as a universal solution for sample preparation. This review aims to show the main advantages and limitations of the above mentioned sample preparation approaches and the applicability and capability of each technique for challenging cases such as complex matrices, on-site applications and automation.

Investigation of liquid chromatography quadrupole time-of-flight mass spectrometry performance for identification and determination of hydroxylated stilbene antioxidants in wine

The performance of liquid chromatography (LC) followed by quadrupole time-of-flight (QTOF) mass spectrometry (MS) for the determination of hydroxylated stilbene compounds in red and white wine samples is assessed. When combined with a solid-phase extraction step, LC-QTOF-MS allowed the selective determination of five target compounds (trans- and cis-resveratrol, trans-piceatannol, trans-piceid and trans-pterostilbene) attaining limits of quantification between 3 and 20ngmL(-1) and providing linear responses up to 4000ngmL(-1). Recoveries, established against standards prepared in methanol, varied between 93% and 115%. The distribution of the above species in wine is illustrated with the analysis of 15 samples. Trans-pterostilbene remained undetected in samples, whereas trans-piceid and trans-resveratrol maximum concentrations exceed the 6000ngmL(-1) level. Values for trans-piceatannol and cis-resveratrol ranged from non detected to 600ngmL(-1), and from 11 to more than 3200ngmL(-1), respectively. Accurate MS and MS/MS scan spectra were used to investigate the existence of reduced (dihydro) and oxidized (dehydro) forms of resveratrol and picetannol in the processed samples. Dihydro derivatives appeared, as free compounds, in 100% (dihydro-piceatannol) and 40% (dihydro-resveratrol) of the samples. On the other hand, dehydro derivatives were noticed as conjugated (glycosylated) species, with detection frequencies of 100% and 47% for dehydro-glucosyl-resveratrol and dehydro-glucosyl-piceatannol, respectively. Above findings confirm the suitability of LC-QTOF-MS for the comprehensive study of hydroxylated stilbene antioxidants in wine samples.