A critical review of solid phase microextraction for analysis of water samples

Rapid and sensitive method for the simultaneous determination of PAHs and alkyl-PAHs in scrubber water using HS-SPME-GC-MS/MS

Scrubber water, a waste stream generated by ships exhaust gas cleaning systems, may pose a threat when released into the marine environment due to potential contamination with polycyclic aromatic hydrocarbons (PAHs) and their alkyl derivatives (alkyl-PAHs). This study aims to develop a reliable analytical procedure combining headspace solid-phase microextraction (HS-SPME) with gas chromatography coupled to triple quadrupole tandem mass spectrometry (GC-MS/MS) to simultaneously separate and determine target compounds in aqueous samples. Method validation demonstrated good linearity up to 200 ng L-1 (r2> 0.996) and low limits of detection (0.33 to 1.67 ng L-1, except for naphthalene at 3.3 ng L-1). The method shows good precision (RSD<20%) and satisfactory analytical recoveries. The methodology was successfully applied to scrubber water samples collected from a container ship and the results highlight the prevalence of naphthalene, phenanthrene, and their alkyl derivatives.•Rapid and reproducible HS-SPME-GC-MS/MS method for the analysis of PAHs and alkyl-PAHs in scrubber water.•The capacity of SPME to analyze both filtered and unfiltered samples was assessed, showing that the more hydrophobic PAHs may be lost during filtration.

Embedding Mixed Sorbents in Binder: Solid-Phase Microextraction Coating with Wide Extraction Coverage and Its Application in Environmental Water Analysis

Solid-phase microextraction (SPME) is a simple and highly effective sample-preparation technique for water analysis. However, the extraction coverage of a given SPME device with a specific coating can be an issue when analyzing multiple environmental contaminants. Therefore, instead of synthesizing one sorbent material with dual or multiple functions, we investigated a new strategy of preparing SPME blades using a homogeneous slurry made by mixing three different sorbent particles─namely, hydrophobic/lipophilic balanced (HLB), HLB-weak cationic exchange (HLB-WCX), and HLB-weak anionic exchange (HLB-WAX)─with a polyacrylonitrile (PAN) binder. The developed coating is matrix compatible, as the binder functions not only as a glue for immobilizing the sorbent particles but also as a porous filter, which only allows small molecules to enter the pores and interact with the particles, thus avoiding contamination from large elements. The results confirmed that the proposed mixed-coating SPME device provides good extraction performance for polar and nonpolar as well as positively and negatively charged compounds. Based on this device, three comprehensive analytical methodologies─high-throughput SPME-LC-MS/MS (for the quantitative analysis of targeted drugs of abuse and artificial sweeteners), in-bottle SPME-LC-high resolution MS (HRMS) (for the untargeted screening of organic contaminants), and on-site drone sampling SPME-LC-HRMS (for on-site sampling and untargeted screening)─were developed for use in environmental water analysis. The resultant data confirm that the proposed strategies enable comprehensive water quality assessment by using a single SPME device.

Polydopamine-functionalized electrospun poly(vinyl alcohol)/chitosan nanofibers for the removal and determination of Cu(II)

Environmentally friendly and recycled polydopamine-functionalized electrospun poly(vinyl alcohol)/chitosan nanofibers (PVA/CS/PDA) were prepared through a low-energy-consumption procedure. The PDA coating endows PVA/CS/PDA nanofibers with good water stability. The PVA/CS/PDA nanofibers have a fibrillar and porous structure that is favorable for Cu(II) to access the active sites of the nanofibers. The adsorption isotherm and kinetics data preferably conform to the Liu isotherm and pseudo-second-order kinetic models, respectively. The maximum adsorption capacity of Cu(II) ions by PVA/CS/PDA nanofibers from the Liu isotherm model is 326.5 mg g-1. The PVA/CS/PDA nanofibers exhibit higher adsorption capacity than some other reported adsorbents. The adsorption mechanism study demonstrates that the Cu(II) adsorption is mainly ascribed to the complexation of Cu(II) with the imino, amino, and hydroxy moieties in PVA/CS/PDA nanofibers. The nanofibers can be employed for 5 cycles without significantly deteriorating performance. More interestingly, a fluorometry method based on the oxidation mimic enzyme activity of Cu(II) was developed to detect low concentrations of Cu(II) using the nanofibers as an adsorbent to preconcentrate Cu(II). The limit of detection is 0.42 mg L-1. The successful removal and detection of Cu(II) in Pearl River and mineral water samples demonstrates the great potential of PVA/CS/PDA nanofibers to remediate Cu(II)-polluted water.

Traditional methods and biosensors for detecting disinfection by-products in water: A review

In recent years, pollution caused by disinfection by-products (DBPs) has become a global concern. Initially, there were fewer contaminants, and the mechanism of their generation was unclear; however, the number of contaminants has increased exponentially as a result of rapid industrialization and numerous economic activities (e.q., during the outbreak of COVID-19 a surge in the use of chlorinated disinfectants was observed). DBP toxicity results in various adverse health effects and organ failure in humans. In addition, it profoundly affects other forms of life, including animals, plants, and microorganisms. This review comprehensively discusses the pre-treatment methods of traditional and emerging DBPs and the technologies applied for their detection. Additionally, this paper provides a detailed discussion of the principles, applicability, and characteristics of traditional large-scale instrumentation methods (such as gas/liquid/ion chromatography coupled with mass spectrometry) for detecting DBPs based on their respective detection techniques. At the same time, the design, functionality, classification, and characteristics of rapid detection technologies (such as biosensors) are also detailed and analyzed.

Solid-Phase Microextraction Techniques and Application in Food and Horticultural Crops

Solid-phase microextraction (SPME) is a sample preparation technique which utilizes small amounts of an extraction phase for the extraction of target analytes from investigated sample matrices. Its simplicity of use, relatively short sample processing time, and fiber reusability have made SPME an attractive choice for many analytical applications. SPME has been widely applied to the sampling and analysis of environmental, food, aromatic, metallic, forensic, and pharmaceutical samples. Solid phase microextraction is used in horticultural crops, for example, to determine water and soil contaminants (pesticides, alcohols, phenols, amines, herbicides, etc.). SPME is also used in the food industry to separate biologically active substances in food products for various purposes, for example, disease prevention, determining the smell of food products, and analyzing tastes. SPME has been applied to forensic analysis to determine the alcohol concentration in blood and that of sugar in urine. This method has also been widely used in pharmaceutical analysis. It is a solvent-free sample preparation technique that integrates sampling, isolation, and concentration. This review focuses on recent work on the use of SPME techniques in the analysis of food and horticultural crops.

Rapid screening of polybrominated diphenyl ethers in water by solid-phase microextraction coupled with ultrahigh-resolution mass spectrometry

Polybrominated diphenyl ethers (PBDEs) are considered emerging organic contaminants that attract more attention in the environment. Herein, online coupling of solid-phase microextraction and ultrahigh-resolution mass spectrometry was developed for rapid screening of eight PBDEs in water samples. This procedure was completed in 22 min, about 6 times faster than the routine workflow such as solid-phase extraction coupled with gas chromatography-mass spectrometry. Thermal desorption and solvent-assisted atmospheric pressure chemical ionization were developed for the effective coupling of solid-phase microextraction (SPME) with ultrahigh-resolution mass spectrometry (UHRMS), which contributed to the signal enhancement and made the methodology feasible for environmental screening. The limits of detection and quantification were 0.01-0.50 ng/mL and 0.05-4.00 ng/mL, respectively. The recoveries were 57.2-75.2% for quality control samples at spiking levels of 0.8-10 ng/mL (4-50 ng/mL for BDE209), with relative standard deviation less than 19.0%. Twelve water samples from different river sites near industrial areas were screened using the developed method. The results showed that BDE-209 was the dominant PBDE (1.02-1.28 ng/mL in positive samples), but its amount was lower than the human health ambient water quality criteria. Consequently, the developed method provides a rapid and reliable way of evaluating contamination status and risks of PBDEs in aqueous environment.

Recent Trends in Multiclass Analysis of Emerging Endocrine Disrupting Contaminants (EDCs) in Drinking Water

Ingestion of water is a major route of human exposure to environmental contaminants. There have been numerous studies exploring the different compounds present in drinking water, with recent attention drawn to a new class of emerging contaminants: endocrine-disrupting compounds (EDCs). EDCs encompass a broad range of physio-chemically diverse compounds; from naturally occurring to manmade. Environmentally, EDCs are found as mixtures containing multiple classes at trace amounts. Human exposure to EDCs, even at low concentrations, is known to lead to adverse health effects. Therefore, the ability to evaluate EDC contamination with a high degree of sensitivity and accuracy is of the utmost importance. This review includes (i) discussion on the perceived and actual risks associated with EDC exposure (ii) regulatory actions that look to limit EDC contamination (iii) analytical methods, including sample preparation, instrumentation and bioassays that have been advanced and employed for multiclass EDC identification and quantitation.

Polyacrylic Acid Functionalized Biomass-Derived Carbon Skeleton with Highly Porous Hierarchical Structures for Efficient Solid-Phase Microextraction of Volatile Halogenated Hydrocarbons

In this study, polyacrylic acid functionalized N-doped porous carbon derived from shaddock peels (PAA/N-SPCs) was fabricated and used as a solid-phase microextraction (SPME) coating for capturing and determining volatile halogenated hydrocarbons (VHCs) from water. Characterizations results demonstrated that the PAA/N-SPCs presented a highly meso/macro-porous hierarchical structure consisting of a carbon skeleton. The introduction of PAA promoted the formation of polar chemical groups on the carbon skeleton. Consequently, large specific surface area, highly hierarchical structures, and abundant chemical groups endowed the PAA/N-SPCs, which exhibited superior SPME capacities for VHCs in comparison to pristine N-SPCs and commercial SPME coatings. Under the optimum extraction conditions, the proposed analytical method presented wide linearity in the concentration range of 0.5-50 ng mL^-1, excellent reproducibility with relative standard deviations of 5.8%-7.2%, and low limits of detection varying from 0.0005 to 0.0086 ng mL^-1. Finally, the proposed method was applied to analyze VHCs from real water samples and observed satisfactory recoveries ranging from 75% to 116%. This study proposed a novel functionalized porous carbon skeleton as SPME coating for analyzing pollutants from environmental samples.

Sponge-like porous manganese(II, III) oxide as a coating for solvent-assisted solid-phase microextraction of polycyclic aromatic hydrocarbons followed by gas chromatography-mass spectrometry

A nanostructure sponge-like porous manganese(II, III) oxide was synthesized and applied as a new fiber coating for solvent-assisted solid-phase microextraction. The synthesized material was characterized via Fourier-transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, X-ray diffraction, and N₂ adsorption/desorption techniques. To investigate the extraction performance of the prepared material, direct immersion solid-phase microextraction followed by gas chromatography-mass spectrometry was used for the determination of the selected polycyclic aromatic hydrocarbons in wastewater samples. Three polycyclic aromatic hydrocarbons including 1-methylnaphthalene, anthracene, and pyrene were selected as model analytes. To maximize the sensitivity of the method, key experimental factors affecting the extraction efficiency of the analytes such as ionic strength, extraction solvent, stirring rate, extraction temperature and time, and desorption temperature and time were optimized. The applicability of the new coating material for the extraction of the selected analytes from wastewater samples was evaluated. Under the optimum conditions, detection limits between 0.7 and 1.5 ng L^-1 were obtained for the model analytes. The linear dynamic range was 5.0-3.0 × 10³ ng L^-1 for all the analytes. Relative standard deviations were between 2 and 11%. In the case of real sample analysis, the extraction recoveries of the analytes were obtained in the range of 77-111%.

ZIF-8/nitrogen-doped reduced graphene oxide as thin film microextraction adsorbents for simultaneous determination of novel halogenated flame retardants in crayfish-aquaculture water systems

Novel halogenated flame retardants (HFRs) have attracted much attention due to their environmental hazard and adverse effects on human health. In this study, a sensitive and simultaneous method for the determination of six novel HFRs was developed, including tetrabromobisphenol A (TBBPA), tetrachlorobisphenolA, TBBPA bis(2-hydroxyethyl ether), TBBPA bis(allyl ether), TBBPA bis(2,3-dibromopropyl ether) and 2,4,6-tris(2,4,6-tribromophenoxy)-1,3,5-triazine. ZIF-8 modified nitrogen-doped reduced graphene oxide (ZIF-8@N-rGO) was synthesized and coated onto a syringe filter to prepare a thin film microextraction (TFME) device. The adsorption capacities of ZIF-8@N-rGO for novel HFRs ranged from 50.98 to 112.84 mg g^-1, exhibiting good extraction efficiency through a combination of π-π, hydrophobic, and hydrogen bonding interactions. The TFME device was coupled to a high-performance liquid chromatography-ultraviolet detection system to simultaneously determine target HFRs in crayfish-aquaculture water systems. Under the optimal extraction parameters, the linearities ranged from 0.1 to 100 ng mL^-1. The method detection limits ranged from 0.030 to 0.14 ng mL^-1 and relative recoveries ranged from 88.6 to 106.2%. We found that novel HFRs were detected in water and crayfish samples and were primarily distributed in the viscera and head shell of the crayfish. The bioconcentration factors ranged from 0.25 to 19.20 L kg^-1, indicating non-bioaccumulation in the crayfish. This study provides valuable technology and information for potential health risks of exposure to novel HFRs from consuming crayfish.

Highly Robust Interfacially Polymerized PA Layer on Thermally Responsive Semi-IPN Hydrogel: Toward On-Demand Tuning of Porosity and Surface Charge

Hydrogel composites with skin layer that allows fast and selective rejection of molecules possess high potential for numerous applications, including sample preconcentration for point-of-use detection and analysis. The stimuli-responsive hydrogels are particularly promising due to facile regenerability. However, poor adhesion of the skin layer due to swelling-degree difference during continuous swelling/deswelling of the hydrogel hinders its further development. In this work, a polyamide skin layer with strong adhesion was fabricated via gel-liquid interfacial polymerization (GLIP) of branched polyethyleneimine (PEI) with trimesoyl chloride (TMC) on a cross-linked N-isopropyl acrylamide hydrogel network containing dispersed poly sodium acrylate (PSA), while the traditional m-phenylenediamine (MPD)-TMC polyamide layer readily delaminates. We investigated the mechanistic design principle, which not only resulted in strong anchoring of the polyamide layer to the hydrogel surface but also enabled manipulation of the surface morphology, porosity, and surface charge by tailoring interfacial reaction conditions. The polyamide/hydrogel composite was able to withstand 100 cycles of swelling/deswelling without any delamination or a significant decrease in its rejection performance of the model dye, i.e., methylene blue. Regeneration can be done by deswelling the swollen beads at 60 °C, which also releases any loosely bound molecules together with absorbed water. This work provides insights into the development of a physically and chemically robust skin layer on various types of hydrogels for applications such as preconcentration, antifouling-coating, selective compound extraction, etc.

Micro-gel thin film molecularly imprinted polymer coating for extraction of organophosphorus pesticides from water and beverage samples

Molecularly imprinted polymers (MIPs) have become an important class of materials for selective and efficient adsorption of target analytes. Despite versatility of MIPs for fabrication in numerous formats, these materials have been primarily reported as solid phase extraction packing materials. An effective thin film MIP prepared on stainless steel substrate is reported here for high throughput enrichment of organophosphorus pesticides (OPPs) from water and beverage samples followed by liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis. The key factors controlling performance as well as best practices for optimized fabrication of thin film MIPs are presented. A pseudo-phase diagram is introduced to evaluate and predict the effect of the ratio of porogen (solvent, 1-octanol) volume to relative crosslinker mass on the desired polymer features (i.e., porosity, surface area, capacity, and selectivity). At low porogen ratios, a macroporous polymer with insignificant selectivity is formed, whereas at high porogen ratios a micro-gel polymer with superior selectivity towards targets is obtained. The porosity and morphology determined with nitrogen adsorption and scanning electron microscopy were attributed to specific regions in the pseudo-phase diagram. Other factors influencing selectivity and stability of the polymer, such as type of the template and its ratios with monomer (methacrylic acid) and crosslinker (ethylene glycol dimethacrylate) were optimized. The prepared thin film MIPs were characterized using adsorption isotherms and adsorption kinetics, and evaluated for matrix effects (high humic acid content) and cross-reactivity in presence of other pesticides and pharmaceuticals. The optimized method provided limits of quantitation (LOQs) ranged from 0.002 to 0.02 ng mL^-1 in water and from 0.095 to 0.48 ng g^-1 in apple juice. Regarding inter-device variability (CV∼10% without normalization), excellent linearity (R² > 0.99), satisfactory accuracies (90-110%) and precisions (<15%) were obtained.

Pharmaceuticals, pesticides and metals/metalloids in Lake Guaíba in Southern Brazil: Spatial and temporal evaluation and a chemometrics approach

Compiling and reporting data related to the presence of pharmaceuticals and pesticides are crucial means of assessing the risk those chemicals pose to human health and environment. Data sets from different sources were combined using a data fusion approach to produce a spatial and temporal variation of contaminants presents in water from Lake Guaíba (29°55'-30°24' S; 51°01'-51°20' W). Lake Guaíba is a 496 km² water body situated in the geological depression of Rio Grande do Sul State, Brazil; that is fed by several rivers from the metropolitan area, the 5th largest metro area in Brazil, with approximately 5 million inhabitants. Analytical methodology to quantify pharmaceuticals and pesticides by LC-QTOF-MS and GC-MS/MS was validated for 41 pharmaceutical and 62 pesticides. Furthermore, 27 chemical elements were analyzed by ICP-MS, and physical chemical parameters were determined using established methodologies. All validation parameters were in accordance with the National Institute of Metrology, Standardization, and Industrial Quality. Thirty-five water samples were analyzed from January to August 2019, and 15 pharmaceuticals and 25 pesticides were present in concentrations ranging from 6.00 ng L^-1 to 580.00 ng L^-1. Twenty-seven elements were analyzed during the same period, and 18 were present in concentrations ranging from 0.2 μg L^-1 to 7060 μg L^-1. Samples were tagged according to the points and months of collection to identify temporal and spatial patterns. The main findings show that the compounds are distributed throughout the studied area without an apparent regular pattern, suggesting that events in a specific point affect the entire ecosystem. Conversely, temporal variations were well defined, as samples were grouped according to the climatic conditions of the months of collection. Considering the calculated quotient risks, atrazine, cyproconazole, diuron, and simazine showed the highest risk levels for algae; acetaminophen, diclofenac, and ibuprofen showed the highest risk levels for aquatics invertebrates.

Metal organic framework derived Zn/N co-doped hydrophilic porous carbon for efficient solid phase microextraction of polar phenols

MOF-derived zink and nitrogen co-doped porous carbon (ZNPC) was synthesized through the pyrolysis of MOF-5-NH₂ and used as a solid-phase microextraction (SPME) coating material. Coupled with gas chromatography-mass spectrometry (GC-MS), headspace SPME (HS-SPME) based on ZNPC was adopted for the determination of phenols in food samples. The co-existence of N and Zn in ZNPC endows the derived carbon superior hydrophilicity, which is highly beneficial for phenols capture. After optimizing the conditions of extraction and desorption, a sensitive analytical method was established with low limits of detections (LODs, 0.73-2.3 ng g^-1) and wide linear ranges (5-5000 ng g^-1). Both the intra-fiber repeatability (RSDs from 2.8-7.3%) and inter-fiber reproducibility (RSDs from 9.7-11.7%) were satisfactory. The established method was applied to phenol determination in beef jerky and duck neck with satisfactory recoveries of 81.2-120.4% and RSDs of 2.8-9.9%, which met well with the requirement of practical application.

A Novel Hydrogen Fluoride Assisted-Glass Surface Etching Based Liquid Phase Microextraction for the Determination of 4-n-Nonylphenol in Water by Gas Chromatography-Mass Spectrometry with Matrix Matching Strategy

A novel extraction method named hydrogen fluoride assisted-glass surface etching based liquid phase microextraction (HF-GSE-LPME) was proposed to determine 4-n-nonylphenol at trace levels by gas chromatography-mass spectrometry (GC-MS). After the evaluation of system analytical performance for the HF-GSE-LPME-GC-MS system, limit of detection (LOD) and limit of quantification (LOQ) values were calculated as 7.1 and 23.8 ng/g, respectively. Enhancement in detection power of the method was determined to be 22 fold when LOD values of the GC-MS and HF-GSE-LPME-GC-MS systems were compared with each other. Applicability and accuracy of the established method were checked by performing spiking experiments. A matrix matching calibration strategy was applied to boost the accuracy of quantification in both matrices, and the percent recovery results obtained for bottled drinking water and dam lake water samples were in the range of 98 - 107 and 90 - 117%, respectively.

Enhanced thread spray mass spectrometry: a general method for direct pesticide analysis in various complex matrices

Determination of pesticide residues in a wide variety of matrices is an ongoing challenge due to low concentration and substantial amounts of interfering endogenous compounds that can be coextracted with the analytes. Herein, we describe the use of cellulose thread both as a suitable sampling medium for various matrices and as a direct analysis platform through an improved thread spray mass spectrometry (MS) approach. Enhanced extraction and the subsequent generation of tiny nanodroplets, after the application of DC potential to the wet thread, enabled ultra-sensitive detection of pesticides without prior sample treatment. This methodology was applied to quantify glyphosate and its metabolite, aminomethylphosphonic acid, in surface water at 12.2 μg mL^-1 limit of detection (LOD) via standard addition calibration. The method was also used for an internal standard calibration for the analysis of atrazine, which resulted in a LOD of 0.74 ng mL^-1. The enhanced thread spray MS platform also proved effective when applied for direct analysis of diphenylamine and thiabendazole, which enabled the evaluation of post-harvest pesticide treatment of fruits (surface and interior) without complete destruction of the fruits.

Ketoenamine Covalent Organic Framework Coating for Efficient Solid-Phase Microextraction of Trace Organochlorine Pesticides

Fiber coating is a key part of solid-phase microextraction (SPME) technology, and it determines the selectivity, sensitivity, and reproducibility of the analytical method. A ketoenamine covalent organic framework called Tp-Azo-COF with rich electronegative N atoms was prepared as an SPME coating in this work. The Tp-Azo-COF coating had a large surface area of 1218 m² g^-1 and good thermal and chemical stability, and it was applied for the extraction of organochlorine pesticides (OCPs). According to quantum chemistry calculations, the adsorption affinity of the Tp-Azo-COF coating for five OCPs was primarily affected by the halogen bond and hydrophobicity interaction. The extraction efficiencies of the Tp-Azo-COF coating for five OCPs were higher than those of three commercial SPME fiber coatings, and the enrichment factors ranged from 1061 to 3693. When combined with gas chromatography-tandem mass spectrometry, a wide linear range (0.1-1000 ng L^-1), low limits of detection (0.002-0.08 ng L^-1), and good fiber-to-fiber accuracy (4.3-10.9%) were achieved under optimal conditions. Moreover, the applicability of the developed method was evaluated by analyzing four samples (milk, green tea, tap water, and well water), and the recoveries were in the range of 83.4-101.6%, with relative standard deviations <8.6%. This research extends the application of the stabilized ketoenamine COF as a sample enrichment probe for OCP analysis.

Catalytic Oxygenation-Mediated Extraction as a Facile and Green Way to Analyze Volatile Solutes

Sparging-based methods have long been used to liberate volatile organic compounds (VOCs) from liquid sample matrices prior to analysis. In these methods, a carrier gas is delivered from an external source. Here, we demonstrate "catalytic oxygenation-mediated extraction" (COME), which relies on biocatalytic production of oxygen occurring directly in the sample matrix. The newly formed oxygen (micro)bubbles extract the dissolved VOCs. The gaseous extract is immediately transferred to a separation or detection system for analysis. To start COME, dilute hydrogen peroxide is injected into the sample supplemented with catalase enzyme. The entire procedure is performed automatically-after pressing a "start" button, making a clapping sound, or triggering from a smartphone. The pump, valves, and detection system are controlled by a microcontroller board. For quality control and safety purposes, the reaction chamber is monitored by a camera linked to a single-board computer, which follows the enzymatic reaction progress by analyzing images of foam in real time. The data are instantly uploaded to the internet cloud for retrieval. The COME apparatus has been coupled on-line with the gas chromatography electron ionization mass spectrometry (MS) system, atmospheric pressure chemical ionization (APCI) MS system, and APCI ion-mobility spectrometry system. The three hyphenated variants have been tested in analyses of complex matrices (e.g., fruit-based drinks, whiskey, urine, and stored wastewater). In addition to the use of catalase, COME variants using crude potato pulp or manganese(IV) dioxide have been demonstrated. The technique is inexpensive, fast, reliable, and green: it uses low-toxicity chemicals and emits oxygen.

Chromatomembrane preconcentration of phenols using a new 3D printed microflow cell followed by reversed-phase HPLC determination

Chromatomembrane process represents a universal approach to the separation of compounds in liquid-gas and liquid-liquid phases systems. However, the broad application of chromatomembrane separation methods in chemical analysis is restricted by the absence of serially produced chromatomembrane flow cells and the difficulties of their laboratory production. The present work addresses the preparation of chromatomembrane flow cell by using 3D printing. Fused deposition modeling and stereolithography were modes for the production of the flow cell using acrylonitrile-butadiene-styrene and polyacrylate-based Anycubic UV resins respectively. The separation and analytical performance of the 3D-printed flow cell were compared with a polyimide unit fabricated by a milling machine, the trial addressing the determination of phenol in the air. The method is based on chromatomembrane absorption of the analytes in 95 μL of the aqueous phase positioned in the cell. Reversed-phase HPLC with fluorimetric detection was applied for the determination of the absorbed analytes. The detection limit of phenols (phenol and m-cresol) in the air was 0.9 μg/m³ by absorption preconcentration time of 10 min. The volumetric flow rate of the analyzed air through the chromatomembrane cell using an electrodriven aspirator was 0.1 L/min.

Comparison of Adsorbents Containing Carbon Nanotubes for Express Pre-Concentration of Volatile Organic Compounds from the Air Flow

New composite adsorbents including silica supports (silica, aerosilogel, and diatomite) and carbon materials (multiwall carbon nanotubes and pyrolytic carbon) have been prepared and characterized. The analytical capabilities of the produced sorbents have been evaluated by their efficiency in the express pre-concentration of volatile organic compounds (butanol and phenols) from the air stream. The prepared surface-layered adsorbents containing multiwall carbon nanotubes placed onto the surface of aerosilogel by use of the carbon vapor deposition method with preloading cobalt nanostructures as a catalyst were found significantly more efficient than traditionally used graphitic carbon-based adsorbents Carbopacks B, C, and X. Additionally, a new adsorbent composed of diatomite Porochrome-3 support coated with a pyrocarbon layer was prepared. This low surface area composited adsorbent allowed both quantitative pre-concentration of phenol and isomeric cresols from the air and their thermal desorption. The developed adsorbents provided fast pre-concentration of selected phenols with a concentration factor of 2 × 103 in 5 min and were used for gas chromatographic determination of analytes in the air at low concentration levels starting from several μg/m3 with a flame ionization detector.

Bibliometric study of volatile compounds in commercial fruits of the Solanaceae family

Abstract Bibliometric analysis is a discipline that allows us to identify knowledge trends, assesses scientific activity and the impact of research through its volume, evolution, visibility, and structure. The present study aimed to carry out a bibliometric study of scientific research that contributes to the knowledge of Volatile Organic Compounds (VOCs) of edible and commercial fruits of Solanaceae family. The research consisted of extracting the information from papers in the Web of Science database. We analyzed and performed the production, visibility, and impact of these papers, also relationships and collaboration between authors using BibExcel and VOSviewer software. As a result, 178 documents were obtained from 2001 to 2017. Tomato is the fruit with the largest number of related articles that are focused on studying compounds responsible for taste, aroma, and biotic and abiotic relationships, as well as studies for identification of the genes responsible for these organoleptic and ecological traits. Papers analyzed are related to the research studies of 491 authors from 239 different organizations distributed in 45 countries. This bibliometric study allowed to identify trends in the knowledge in VOCs with respect to Solanaceae fruits, as well as recognizing the location of the scientific material in this field.

Electromagnetically-vibrated solid-phase microextraction for analysis of aqueous-miscible organic compound transport in soil columns

Current methods of sampling pore water from soil columns to determine solute concentrations are slow and require relatively large volumes. Accordingly, an electromagnetically-vibrated (EMV) solid-phase microextraction (SPME) device was evaluated for determining temporal and spatial distributions of solute pore-water concentrations (solute concentration profiles) for four organic compounds, two polar (2-hexanone, 2,4-dimethyl phenol) and two nonpolar (toluene, 1,4-dichlorobenzene), in columns packed with simulated aquifer sands with different fractions of organic carbon. In batch equilibrium extraction tests, the equilibrium extraction time of the organic compounds in aqueous mixtures decreased from 30 to less than 10 min as the frequency of electromagnetic vibration increased from zero to 250 Hz. Mixture effects were not statistically significant (p > 0.05) in the extraction process using EMV SPME. Comparisons of the solute concentration profiles within the soil columns at different elapsed times measured by pore-water samples and in situ EMV SPME extractions revealed both methods were equally effective. However, EMV SPME extraction removed no solution volume and only 0.6-14% of the solute mass removed by the pore-water sample collections, substantially minimizing disturbances to solute transport and fate. Thus, the equilibrium extraction-based calibration method using EMV SPME offers an effective approach for rapidly and accurately determining solute concentration profiles in column tests with negligible solute mass loss and minimal solution flow disturbance.

Microextraction and its application for petroleum and crude oil samples

Petroleum is an extremely heterogeneous material. It consists of a wide range of aliphatic, aromatic, and compounds containing heteroatoms such as metals, sulfur, and nitrogen. The American Society for Testing and Materials (ASTM) methods are used globally as accepted analytical methods for petroleum, petrochemicals, and fuels. A major drawback of ASTM methods is that they require multistep sample preparation that consumes substantial volumes of samples. Thus, the challenge in the petrochemical analysis is to develop rapid and simpler sample preparation procedures that can be automated. An assessment based on the current literature, specifically on the sample preparation of petroleum samples, leads to the authors' conclusion that microextraction provides an excellent complement to current methods. In this review, solvent and sorbent-based microextraction techniques in the context of the consideration of petroleum and crude oil, and samples related to the petrochemical industry, are discussed.

Determination of pesticides of different chemical classes in drinking water of the state of Santa Catarina (Brazil) using solid-phase microextraction coupled to chromatographic determinations

The evaluation of the concentration of pesticides in drinking water presents a real concern. In this study, a simple and rapid method based on solid-phase microextraction (SPME) followed by gas chromatography-mass spectrometry and electron capture detectors was developed aiming at multiclass determination of 23 pesticides regulated by the Brazilian legislation. The extraction was carried out by direct immersion mode (DI-SPME) using DVB/Car/PDMS fiber coating. In order to improve the extraction efficiency, parameters such as temperature, salting-out effect, and extraction time were optimized. The method was evaluated using drinking water samples spiked with the analytes at different concentrations, and it showed good linearity in the range studied. The values obtained for limits of quantification (LOQ) were below the limits established by Brazilian regulations. Accuracy and precision of the method exhibited satisfactory results, providing relative recoveries from 70 to 123.34% at three spiked levels, and the relative standard deviations ranged from 0.53 to 24.8%. The method was applied in 20 drinking water samples from 13 cities in the State of Santa Catarina, Brazil.

Advancements of chiral molecularly imprinted polymers in separation and sensor fields: A review of the last decade

Since chiral recognition mechanism based on molecularly imprinted polymers immerged, it has assisted countless chemical and electrochemical analytical sample preparation techniques. It has done this by enhancing the enatioseparation abilities of these techniques. The preparation and optimization of chiral molecularly imprinted polymers (CMIPs) are two favored methods in the separation and sensor fields. This review aims to present an overview of advances in the preparation and application of CMIPs in analytical approaches in different available formats (eg. column, monolithic column, cartridge, membrane, nanomaterials, pipette tip and stir bar sorptive) over the last decade. In addition, progress in the preparation and development of CMIPs-based sensor fields have been also discussed. Finally, the main application challenges of CMIPs are also summarily explained, as well as upcoming prospects in the field.

Trends in sample preparation and separation methods for the analysis of very polar and ionic compounds in environmental water and biota samples

Recent years showed a boost in knowledge about the presence and fate of micropollutants in the environment. Instrumental and methodological developments mainly in liquid chromatography coupled to mass spectrometry hold a large share in this success story. These techniques soon complemented gas chromatography and enabled the analysis of more polar compounds including pesticides but also household chemicals, food additives, and pharmaceuticals often present as traces in surface waters. In parallel, sample preparation techniques evolved to extract and enrich these compounds from biota and water samples. This review article looks at very polar and ionic compounds using the criterion log P ≤ 1. Considering about 240 compounds, we show that (simulated) log D values are often even lower than the corresponding log P values due to ionization of the compounds at our reference pH of 7.4. High polarity and charge are still challenging characteristics in the analysis of micropollutants and these compounds are hardly covered in current monitoring strategies of water samples. The situation is even more challenging in biota analysis given the large number of matrix constituents with similar properties. Currently, a large number of sample preparation and separation approaches are developed to meet the challenges of the analysis of very polar and ionic compounds. In addition to reviewing them, we discuss some trends: for sample preparation, preconcentration and purification efforts by SPE will continue, possibly using upcoming mixed-mode stationary phases and mixed beds in order to increase comprehensiveness in monitoring applications. For biota analysis, miniaturization and parallelization are aspects of future research. For ionic or ionizable compounds, we see electromembrane extraction as a method of choice with a high potential to increase throughput by automation. For separation, predominantly coupled to mass spectrometry, hydrophilic interaction liquid chromatography applications will increase as the polarity range ideally complements reversed phase liquid chromatography, and instrumentation and expertise are available in most laboratories. Two-dimensional applications have not yet reached maturity in liquid-phase separations to be applied in higher throughput. Possibly, the development and commercial availability of mixed-mode stationary phases make 2D applications obsolete in semi-targeted applications. An interesting alternative will enter routine analysis soon: supercritical fluid chromatography demonstrated an impressive analyte coverage but also the possibility to tailor selectivity for targeted approaches. For ionic and ionizable micropollutants, ion chromatography and capillary electrophoresis are amenable but may be used only for specialized applications such as the analysis of halogenated acids when aspects like desalting and preconcentration are solved and the key advantages are fully elaborated by further research. Graphical abstract.

Development of a solid-phase microextraction method for fast analysis of cyclic volatile methylsiloxanes in water

Cyclic volatile methylsiloxanes (cVMS) are widely used in consumer products and commonly detected in the environment. There are challenges in the analysis of cVMS because of their ubiquitous use which can introduce high background contamination. The current study introduces a sample preparation method based on headspace of solid-phase microextraction (SPME) for monitoring the cVMS in waters. Efforts were made to reduce the background contamination during sample preparation and instrument analysis. A laboratory prepared MIL-101 coating was prepared using polysulfone instead of polydimethylsiloxane as adhesive to avoid the contamination. The extraction performance of the MIL-101 fiber was optimized and evaluated. The optimized extraction time and temperature were 60 min and 40 °C, respectively. The method quantification limits of the MIL-101 fiber for octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5) and dodecylcyclohexasiloxane (D6) in water were 0.15 ng mL^-1, 0.14 ng mL^-1, and 0.27 ng mL^-1, respectively. The extraction efficiency of the proposed MIL-101 fiber was comparable to the commercial polydimethylsiloxane/divinylbenzene fiber. The developed method was applied to analyze the cVMS in wastewater treatment plant and the concentrations in the barscreen and in the aeration tank ranged from 0.73 to 3.3 ng mL^-1 and 7.74-85.1 ng mL^-1, respectively. The MIL-101 fiber was also applied to study the photodegradation of the cVMS in water under simulated sunlight. Approximately 25%, 20%, and 45% of D4, D5, and D6, respectively, were degraded after 10 h exposure.