Sorptive Phase Research Articles

Humic acid-coated paper: An affordable mixed-mode weak-cation exchanger for isolating cocaine, codeine, and methadone from saliva samples for their direct infusion mass spectrometric analysis.

The use of natural materials as precursors for synthesizing sorptive phases can reduce the environmental impact of the sample preparation step. In this article, two natural materials, i.e., cellulose and humic acids, are combined, resulting in a porous and flat sorptive phase that combines hydrophobic and cation exchange interactions. The simple preparation, with low reagent consumption, and the high production capacity make this process affordable. The performance of the humic acid-coated paper has been studied towards three basic drugs (cocaine, codeine, and methadone), and it has allowed the determination of the targets in saliva by direct infusion tandem mass spectrometry. The simultaneous extraction of many samples and the rapid analysis (2 min) provide a high sample throughput. The resulting method has been validated following the International Conference on Harmonization (ICH) M10 validation guide. Working at the optimum conditions, the linear range was established from 5 to 500 μg·L-1 and the detection limits were established at 1.5 μg·L-1 for all the analytes. At the LOQ, the inter-day precision and intra-day precision, expressed as relative standard deviation, were better than 13.6% and 17.9%, respectively. For low/mid/high quality controls, the inter-day precision and intra-day precision were better than 11.8% and 9.1%, respectively. The accuracy, calculated as relative recovery, was in the range of 83.8-106.1%. Several samples from patients under treatment with codeine-containing prescriptions were finally analyzed.

On-site extraction of benzophenones from swimming pool water using hybrid tapes based on the integration of hydrophilic-lipophilic balance microparticles and an outer magnetic nanometric domain

An on-site extraction device is presented consisting of scotch tape modified with concentric domains of micrometric hydrophilic-lipophilic balance (HLB) particles surrounded by a ring of nanometric magnetic ones. On the one hand, HLB microparticles are readily available at the surface of the tape, exposed to interact with the target analytes, being responsible for the extraction capacity of the sorptive phase. On the other hand, the presence of magnetic nanoparticles enables the attachment of the modified tape onto a metallic screw via a magnet, which is then coupled to a wireless drill, enabling the stirring of the microextraction device. Both are simply fixed to the cost-effective, flexible, and versatile support, i.e., scotch tape, owing to their adhesive properties. The microextraction device has been applied to the determination of six benzophenones in swimming pool water samples. The variables that may affect the extraction process have been evaluated. Under the optimum conditions and using liquid chromatography-tandem mass spectrometry as the instrumental technique, the method provided a limit of detection of 0.03 µg L−1. The intra-day precision, evaluated at three different concentration levels and expressed as relative standard deviation, was lower than 10%, which also comprises the variability within single-use sorptive tapes. The accuracy, calculated with spiked samples and expressed as relative recovery, ranged from 71 to 138%. The method was applied to the analysis of swimming pool water, revealing the presence of such compounds.Graphical

Mixed-mode cationic exchange paper combined with direct infusion mass spectrometry, a sustainable approach to determine opioids in biosamples

Direct infusion mass spectrometry (DI-MS/MS) allows the rapid analysis of samples and minimizes solvent usage by avoiding chromatographic separation. However, it is prone to ion suppression due to matrix effects, especially when biosamples are processed. In this context, sample preparation appears as the perfect complement to get proper analytical results. In this article, a novel and sustainable planar sorptive phase containing mixed-mode cationic exchange (MCX) particles is presented to overcome the limitations of DI-MS/MS in bioanalysis. The new phase uses cellulose paper as a natural substrate over which the particles can be retained using polyacrylonitrile (PAN) as the chemical binder. The high porosity of the cellulose substrate simplifies the synthesis since a straightforward dip-coating technique can be applied. For this purpose, MCX particles are initially dispersed in a PAN solution prepared in N,N-Dimethylformamide. A segment of paper is later introduced into the slurry, and the evaporation of the solvent leaves a film of PAN-MCX composite over the paper, where the particles are entrapped but accessible for the analyte's isolation. The resulting MCX-paper has been evaluated for the extraction of selected opioids (codeine, methadone, morphine, naloxone, oxycodone, and tramadol) from saliva and urine samples and their determination by direct infusion tandem mass spectrometry. Working at the optimized conditions, the limits of detection were in the low μg L−1 range. The precision, expressed as relative standard deviation, was better than 12 % under intra-day and inter-day conditions. The accuracy, expressed as relative recoveries, provides values in the ranges 89–113 % and 74–121% for saliva and urine, respectively. The method was finally applied to analyze saliva and urine samples collected from patients under codeine treatment.

Sexual hormones monitoring in surface waters and wastewaters from Northern Italy by thin film microextraction coupled with HPLC-MS/MS.

The occurrence of sex steroid hormones, viz. oestrogens and progestins, in aquatic ecosystems is of global concern due to their role as endocrine disrupting chemicals, even at low concentration (μg L-1 or less). Thus, it is essential to monitor these organic pollutants to get a realistic picture of their presence and to control their contamination levels in environmental water bodies. In this respect, we have explored the use of self-prepared polymeric films as novel sorptive phase for the microextraction of 17β-estradiol, 17α-ethinylestradiol, estrone, progesterone, medroxyprogesterone acetate and hydroxyprogesterone. The thin film microextraction procedure has been developed, evaluating different film compositions, sample volumes and elution conditions to recover the sorbed analytes. The overall method provides good reproducibility (RSD < 12%) and recoveries higher than 60%. The final method has been applied to environmental monitoring in surface waters (river and lake samples) and urban wastewater treatment plant effluents and influents from Northern Italy, to get a contamination snapshot of this highly urbanized area.

Transport of reactive contaminant in a wetland flow with the effects of reversible and irreversible reactions on the bed surface

Wetlands are crucial for maintaining biodiversity in ecosystems. The reversible chemical reactions can significantly affect the pollutant reduction capacity in wetland flow. The spatial transport of contaminants in wetlands is further complicated by phase exchange kinetics due to reversible reactions in the wetland bed. This paper provides an analytical solution for studying the multi-dimensional concentration distribution of solutes in wetland flow, considering both reversible and irreversible boundary reactions. Unlike previous one-dimensional studies (Jiang et al. (2022), Zhan et al. (2024)), our approach offers a comprehensive view of wetland contaminant transport, accounting for complex interactions between different phases and environmental factors. The solute may undergo reversible sorptive phase exchange between the immobile (wetland bed phase) and the mobile phase (fluid phase). Multi-scale homogenization methods are used to determine the dispersion coefficient, mean concentration, longitudinal and vertical real concentration distributions, rate of variation of vertical concentration distribution under the influence of vegetation force, and reversible and irreversible reactions at a stationary wetland bed. The effects of retention parameter (θ), Damkohler number (Da), vegetation effect (α), dispersion time (τ), and first-order irreversible boundary reaction (β′) on solute mixing are thoroughly analyzed. The study's analytical results are validated by numerical results obtained using the finite difference method with a Shishkin mesh, and other comparisons are made with the limiting case of Taylor dispersivity. Results show that an increase in Damkohler number and vegetation force weakens contaminant transport in wetland flow, but an increase in Da enhances contaminant concentration in the mobile phase. The presence of reversible phase exchange kinetics causes non-uniform vertical concentration variation across the wetland cross-section. Critical values where the multi-scale homogenization technique may fail are suggested as θ≤0.5 and Da≥1. The study's findings have potential applications to pollution control in wetlands.

Green synthesis of MIL53(Al)-modified paper-based analytical device for efficient extraction of neonicotinoid insecticides from environmental water samples

BackgroundThere is a need to develop low-cost, reliable and portable devices to enhance the efficiency of microextraction techniques in complex samples. Metal-organic frameworks (MOFs) have proven to be promising sorbents due to their well-documented properties. However, their green preparation and combination with paper-based substrates have not been satisfactorily explored to fabricate sustainable sorptive phases. ResultsIn this work, the hybridization of a paper substrate (as a sustainable support) with MOFs (as a sorptive phase) was carried out by one-pot approach. Concretely, the selected MOF, MIL-53(Al), was in-situ growth onto the paper surface in aqueous solution without the need for high temperature or pressure, thereby aligning with the Green Analytical Chemistry principles. The optimized composite (MIL-53(Al)@cellulose paper) was characterized and evaluated as extraction sorbent for five neonicotinoids (NEOs) (thiamethoxam, clothianidin, imidacloprid, acetamiprid, and thiacloprid). Furthermore, its feasibility was demonstrated by isolating these pollutants from environmental water samples, followed their determination by HPLC coupled to diode array detection. The whole method showed satisfactory analytical performance with recoveries between 86 and 114 %, suitable precision (with RSD lower than 14 %), and limits of detection ranged from 1.0 to 1.6 μg L−1. Besides, the greenness of the method was assessed by application of different existing metrics. The developed extraction device was affordable (<0.08 €/device) and mechanical and chemically stable, being possible its reuse more than 11 cycles, thus demonstrating its suitability for rapid screening of pesticides in environmental samples. SignificanceThis report presents, for the first time, the green synthesis of MIL-53(Al)cellulose paper composite and its application as a sorptive phase for the extraction of NEOs from environmental water samples. We believe that the proposed strategy for fabricating these sustainable paper-based sorptive phases paves the way for further hybridizations with other MOFs or materials. Additionally, it opens up large possibilities for their application in extraction of pollutants or other hazardous compounds in aquatic environments.

Evaluation of polypropylene microporous membranes as extraction devices for determination of carcinogenic aromatic amines in smoker urine by GC–MS/MS

Exposure to tobacco smoke is highly correlated to the incidence of different types of cancer due to various carcinogenic compounds present in such smoke. Aromatic amines, such as 1-naphthylamine (1-NA) and 2-naphthylamine (2-NA), are produced in tobacco burning and are linked to bladder cancer. Miniaturized solid phase extraction techniques, such as microporous membrane solid phase extraction (MMSPE), have shown potential for the extraction of aromatic compounds. In this study, a bioanalytical method for the determination of 1-NA and 2-NA in human urine was developed using polypropylene microporous membranes as a sorptive phase for MMSPE. Urine samples were hydrolyzed with HCl for 1 h at 80 °C, after which pH was adjusted to 10. Ultrasound-assisted MMSPE procedure was optimized by factorial design as follows. To each sample, 750 µL of methanol was added, and ultrasound-assisted MMSPE was conducted for 1 h with four devices containing seven 2 mm polypropylene membrane segments. After extraction, the segments were transferred to 400 µL of hexane, and desorption was conducted for 30 min. Extracts were submitted to a simple and fast microwave-assisted derivatization procedure, by the addition of 10 µL of PFPA and heating at 480 W for 3 min, followed by clean-up with phosphate buffer pH 8.0 and GC–MS/MS analysis. Adequate linearity was obtained for both analytes in a range from 25 to 500 µg L−1, while the multiple reaction monitoring approach provided satisfactory selectivity and specificity. Intra-day (n = 6) and inter-day (n = 5) precision and accuracy were satisfactory, below 15 % and between 85 and 115 %, respectively. Recovery rates found were 91.9 and 58.4 % for 1-NA and 2-NA, respectively, with adequate precision. 1-NA was found in first-hand smokers’ urine samples in a concentration range from 20.98 to 89.09 µg in 24 h, while it could be detected in second-hand smoker's urine samples, and 2-NA detected in all first and second-hand smokers’ urine samples. The proposed method expands the applicability of low cost MMSPE devices to aromatic amines and biological fluids.

Polyvinyl chloride coated paper postmodified by nucleophilic substitution with diphenylamine to enhance cation-π interactions with opioids in saliva samples

This article evaluates the potential of cellulose paper as a substrate for preparing a polyvinylchloride (PVC)-diphenylamine sorptive phase that can be used under the thin film microextraction (TFME) format. This phase was easily synthesized using the dip-coating technique to coat the filter paper with PVC, followed by the covalent bonding of diphenylamine. As a result, aromatics rings are available on paper surface to isolate the target analytes by a mixed-mode interaction at physiological pH. The resulting material was characterized by infrared spectroscopy, UV–Vis diffuse reflection spectroscopy, and scanning electron microscopy. As analytical problem, three opioids (methadone, codeine, and tramadol) were determined in saliva samples by direct infusion mass spectrometry. Different variables involved in the extraction procedure have been optimized (e.g. sample pH, extraction time, and sample dilution). The proposed method provides good linearity (R2 > 0.9817) and sensitivity (detection limits in the range from 1.5 µg L−1 to 15 µg L−1). The intra-day and inter-day precision, expressed as relative standard deviation, were better than 16.4 % and 18.5 % respectively. The accuracy, expressed as relative recovery, provides values in the interval from 82 % to 105 %. Finally, the proposed approach has been successfully applied to real saliva samples of patients under codeine and tramadol medical prescription.

Effect of phase exchange kinetics on Taylor dispersion of chemically reactive solutes in an oscillatory magnetohydrodynamics flow between two parallel plates

The study of kinetic sorptive effects on the transport phenomena of reactive solute has numerous real-world applications, including in the industrial and environmental sectors. These kinds of investigations become more realistic when an oscillatory pressure gradient with both the reversible and irreversible reactions at the channel walls is considered in a magnetohydrodynamics flow. In the past, Ng and Yip [J. Fluid Mech. 446, 321–345 (2001)] studied the effect of sorptive phase exchange at boundaries on the solute transport phenomena in an open-channel flow using Mei's multiple-scale homogenization technique. They considered fluid flows without magnetic field and boundary absorption. This work uses the above-mentioned method to investigate the phase exchange kinetics of Taylor dispersion phenomena in a two-dimensional magnetohydrodynamics fluid flowing through a parallel channel. The paper discusses how various parameters and dimensionless numbers, such as the Hartmann, oscillatory Reynolds, and Damkohler, affect the flow velocity, transport coefficient, multi-dimensional concentration distributions, and transverse variation rate. Due to the strong magnetic field, the flow velocity and Taylor dispersivity are adversely affected and conspicuously reduced. Additionally, for large Damkohler numbers, the total dispersion coefficient and the Taylor dispersion coefficient both decrease. However, the longitudinal concentration distribution rises with the Hartmann number and partition coefficient. It is worth noting that in the presence of unequal boundary absorption, there is no occurrence of transverse symmetry in solute concentration at any given time. Controlling various processes of tracer dispersion in environmental systems, especially water purification and the chemical industry, may benefit from these intriguing findings.

Biochar-based polymeric film as sustainable and efficient sorptive phase for preconcentration of steroid hormones in environmental waters and wastewaters

BackgroundThe environmental impact of sample preparation should be minimized through simplification of the procedures and the use of natural, renewable and/or reusable materials. In such scenario, thin-film microextraction fulfils the former criteria, as it enables few steps and miniaturization, thus small amount of extraction phase. At the same time, the use of sorbents such as biochars obtained from biomass waste is even more promoted due to their availability at low cost and increased life-cycle in a circular economy vision. However, it is not always easy to combine these criteria in sample preparation. ResultsA thin film microextraction was developed for the determination of steroids in aqueous samples, entailing a membrane made of cellulose triacetate and a wood-derived biochar (Nuchar®) as carbon precursor. Different characterization techniques showed the successful preparation, whereas the sorption kinetics experiments demonstrated that biochar is responsible for the extraction with the polymer acting as a smart support. After a study about membranes’ composition in terms of biochar amounts (4 %, 10 %, 16 % wt) and type of synthesis set up, the ceramic 3D-mold was selected, achieving reproducible and ready-to-use membranes with composition fixed as 10 %. Different elution conditions, viz. type and time of agitation, type, composition and volume of eluent, were evaluated. The final microextraction followed by HPLC-MS/MS quantification was successfully validated in river and wastewater treatment plant effluent samples in terms of accuracy (R% 64–123 %, RSD<19 % in river; R% 61–118 %, RSD <18 % in effluent, n = 4), sensitivity (MQLs 0.2–8.5 ng L−1) and robustness. SignificanceThis novel biochar-based polymeric film proved to be a valid and sustainable sorbent, in terms of extraction capability, ease of preparation and greenness. By comparison with literature and the greenness evaluation with the most recent metric tools, this method expands the potential applicability of the thin-film microextraction and opens up innovative scenarios for sustainable procedures entailing the use of biochars entrapped in bio-polymers.

Cork-Activated Carbon as a Sorptive Phase for Microextraction of Emerging Contaminants in Water Samples

A novel strategy for microextraction of emerging contaminants was developed by using cork activated carbon (CAC) as the sorbent phase. Carbonization of the natural phase increased the surface area and the porosity of the material, thus improving the extraction efficiency. Moderately polar compounds, such as ibuprofen and its metabolites, were used as model analytes in water samples. Rotating disk sorptive extraction (RDSE) together with gas chromatography‒mass spectrometry (GC‒MS) were used for extraction and determination of the analytes, respectively. The optimum conditions for the material synthesis were 600 °C, K2CO3 as the activating agent and a mass ratio of 0.8:1 (activating agent:raw material). The optimum values for the RDSE were pH 2, a sample volume of 25 mL and an extraction time of 90 min. The absolute recovery rates for ibuprofen and its metabolites ranged from 19 to 55%, and the relative standard deviations were between 3 and 13%. The proposed method was used to measure the analytes in the influent and effluent from a wastewater treatment plant in Santiago, Chile. The concentrations found for ibuprofen and its metabolites were 0.98–9.8 µg L-1 and 0.8–8.6 µg L-1 in the influent and effluent, respectively. Activation of the cork material enabled the synthesis of a sorbent phase with sorption efficiencies similar to those obtained with the commercial octadecylsilane (C18) phase and superior to that observed for styrene-divinylbenzene (S-DVB). This process is simple and cost-effective.

Carbon nanotubes in high internal phase emulsion polymer composite for packed-cartridge micro-solid-phase extraction of fluoroquinolones in urine

Aim of this study stands in the evaluation of a carbon nanotubes-based polymerized high internal phase emulsion composite (CNT/polyHIPE) as sorptive phase in biological sample preparation. A micro-solid-phase extraction procedure (µSPE) was developed for trace fluoroquinolone (FQ) antimicrobials, namely Ciprofloxacin, Levofloxacin, Lomefloxacin, Moxifloxacin, Norfloxacin and Sparfloxacin, in human urine samples. PolyHIPEs modified by incorporation of different concentrations of nanotubes (0.2–0.8 wt %) were one-pot synthesized and applied in the packed-cartridge setting. The sorption affinity for the drugs was investigated in tap water and buffered aqueous solutions, demonstrating the key role of the nanotubes embedded in the polymer. The 0.5 wt % CNT composite was selected to develop a straightforward µSPE procedure directly in raw urine (1 mL sample), followed by HPLC-MS/MS. Targets were retained on the sorbent at near neutral pH and, after an aqueous washing (0.1 % v/v formic acid), eluted in a single-step with 4 % v/v ammonia aqueous solution (15 % v/v acetonitrile), thus combining extraction and clean-up. The method allowed accurate quantification of FQs, as evidenced by the recoveries (74–116 %, n = 3) obtained on blank pooled urine samples spiked with 40, 75, 150 µg L−1, accompanied by good inter-day precision (RSD < 14 %, n = 3). To confirm the applicability of the analytical method, some real-life blind samples were processed as a proof of concept.

ZIF67-derived porous carbon-reinforced electrospun nanofiber as an extractive phase for on-chip micro-solid-phase extraction of antifungals from biological fluids prior to liquid chromatography tandem mass spectrometry.

With a view to improving applicability as a sorbent while overcoming the challenges associated with its powdery nature, cobalt-doped zeolitic imidazolate framework (ZIF 67)-derived nanoporous carbon (Co-NPC) was employed as an additive in nanofiber through the process of electrospinning. X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and Brunauer-Emmett-Teller (BET) surface area analysis were used to characterize the resulting nanocomposite. A microfluidic chip device with four layers, including two layers entailing spiral channels, was designed and employed to assess the analytical performance of the fabricated Co-NPC-reinforced electrospun composite. To do so, a folded piece of electrospun composite was sandwiched between two layers with spiral channels. Therefore, both sides of the folded composite acted as a sorptive phase to extract antifungal drugs as target analytes. The significant factors affecting the efficiency of the extraction process were investigated and optimized. Subsequently, the technique was verified through the utilization of liquid chromatography-tandem mass spectrometry (LC-MS/MS) by employing optimal parameters. The optimal conditions were applied to evaluate the figures of merit. A linear range was obtained for antifungal drugs within the range 0.25-200.0ngml-1 with an R2 value of ≥ 0.9914. The method demonstrated detection limits ranging between 0.08 and 0.40ngml-1. The intra-day and inter-day precisions were less than 6.9%. Relative recoveries exhibited variations between 91.4-106.8%, 95.9-103.6%, and 96.4-109.3% for ketoconazole, clotrimazole, and miconazole, respectively. The proposed approach yielded satisfactory results, demonstrating its efficiency.

Onsite Environmental Extraction Based on Portable and Affordable Stirred Devices

Environmental compartments are characterized by their large size and the heterogeneous distribution of the target analytes. Onsite extraction procedures are especially useful in this scenario, allowing the development of ambitious sampling campaigns (including a larger number of locations and periods). This article outlines the relevance of extraction techniques, including exhaustive and non-exhaustive ones, in onsite strategies. However, only stirred units are discussed and described in detail. The discussion of the analytical performance (for example, sensitivity and precision) is intentionally avoided to focus the attention on the devices that can be applied (selecting the sorptive phase) to almost any analytical problem. The impact of open technologies (microprocessors and 3D printing) in the design of these units is also presented.

Deep eutectic solvent coated paper: Sustainable sorptive phase for sample preparation

Paper-based sorptive phases have gained attention recently due to the low-cost and sustainable character of the cellulosic substrate. However, the sustainability of the resulting phase can be limited by type of coating used for analytes isolation. In this article, this limitation is overcome by using deep eutectic solvents (DES) as coating. To this aim, a Thymol-Vanillin DES is synthesized and deposited on pre-cut cellulose paper strips. The paper-supported DES is employed as sorptive phase for the isolation of selected triazine herbicides for environmental waters analysis. The isolated analytes are finally determined by gas chromatography-mass spectrometry using selected ion monitoring. The method is optimized according to the critical variables that potentially affect its analytical performance such as sample volume, extractant amount, extraction time and sample ionic strength. The method was characterized in terms of sensitivity, accuracy and precision and its applicability was evaluated for the analysis of real environmental water samples. Good linearity values (R2>0.995) were obtained for all the analytes. Limits of detection (LODs) ranged from 0.4 to 0.6 µg L−1 and the precision, expressed as relative standard deviation (RSD) was better than 14.7%. The relative recoveries, calculated in spiked well and river samples, were in the range 90–106%.

Lab in a bottle, open-source technologies for the design of affordable environmental samplers integrating on-site extraction

Access to clean water, a Sustainable Development Goal, can only be accomplished worldwide using affordable technologies. In the analytical chemistry realm, developing cheap devices capable of on-site extraction results in a helpful tool. This article presents a new device based on open-source technologies for the on-site extraction of isoflavones from environmental waters as a proof of concept. The device is wholly operated by an Arduino microcontroller that also integrates sensors (temperature and conductivity) to provide on-site information. The extraction unit stirs into the sample, using a small motor, a planar sorptive phase consisting of Mixed-mode Anionic Exchange particles (MAX). After the on-site extraction, the sorptive phase is transported to the lab for its final analysis by liquid chromatography coupled with mass spectrometry. The analytical method provided detection limits of 1.5 ng L−1 (biochanin A and formononetin) and 15 ng L−1 (daidzein and genistein). The precision, expressed as relative standard deviation, was evaluated at three concentration levels providing results better than 9.8 %. The accuracy, with relative recoveries in the 85–119 % ranges, supports the application of the method. The relevance of isotopically labeled compounds to normalize the effect of some variables on the extraction of the analytes is also discussed in detail.

A thin biofilm of chitosan as a sorptive phase in the rotating disk sorptive extraction of triclosan and methyl triclosan from water samples

The features and nature of the sorptive phase may be the stage that determines the scope of microextraction techniques. In search of new alternatives, materials of natural origin have recently been explored to establish greener analytical strategies. Based on that search, this research proposes the use of chitosan as a sorptive phase, which was assessed in the rotating disk sorptive extraction of emerging contaminants from aqueous systems. Chitosan is a biopolymer of animal origin that is usually found in the shells of crustaceans. The main characteristic of this material is the presence of a high number of nitrogenous groups, which gives it high reactivity, but its main disadvantage is associated with its high swelling capacity.In this research, chitosan was crosslinked with a low concentration of glutaraldehyde to form thin films that were easily immobilized on the surface of the rotating disk. The main advantage of this modification is the considerable decrease in the swelling capacity, which prevents loss and rupture of the sorbent during high rotation of the disk. In addition, it not only improved the physical characteristics of chitosan but also increased its extraction capacity. With regard to its use as a sorptive phase, all the variables associated with the microextraction of the analytes were studied, and optimal variables were found to be: pH 4, 20% NaCl (salting out effect), 30–45 min as equilibrium time and elution of analytes with a mixture of methanol:ethyl acetate (1:1).Validation of the methodology for the determination of methyl triclosan and triclosan was carried out, and relative recoveries between 89 and 96% and relative standard deviations less than 14% were found. The detection limits were 0.11 and 0.20 μg L−1, respectively. Through its application in real samples (natural and residual waters), triclosan was quantified between 0.7 and 1.3 μg L−1. Finally, the “green” properties of the phase were evaluated, demonstrating that it is reusable for at least three cycles and biodegradable. Compared to its efficiency with a commercial phase (in this case, the styrene divinyl benzene phase), the proposed biosorbent provided a similar and even higher sorptive capacity (depending on the analyte).

Polyamide-coated paper-based sorptive phase applied in high-throughput thin film microextraction designed by 3D printing

A new method was developed for the determination of endocrine disrupting compounds (phthalates, alkylphenols and bisphenols) in water samples by using thin film microextraction technique (TFME) with high-performance liquid chromatography and diode-array detection (HPLC-DAD). This paper reports for the first time the use of a paper-based sorptive phase (PSP) in a high-throughput semi-automated system. This system designed by 3D printing technology allowed us to integrate the PSP with a multi-well plate format. Multivariate design of experiments and one-factor-at-a-time approaches were employed for optimization. The optimized PSP preparation required two dips of the filter paper into the nylon 66 solution followed by the evaporation of the solvent. The best conditions for the extraction step were NaCl 30 % (w/v) added to the sample at pH 2 for 180 min. The desorption showed best results with acetonitrile for 20 min. The calibration curves exhibited coefficients of determination higher than 0.9837. The limits of detection varied from 1.5 to 7.6 μg L-1. Six of ten analytes showed promising results with accuracy ranging from 82 to 117 % and precision (RSD) equal or inferior to 24 % for mineral water sample. We also evaluated a coconut water sample that obtained higher deviations than mineral water sample. The time consumed for each sample was about 8.3 min.

Chemometers: an integrative tool for chemical assessment in multimedia environments.

We propose novel chemometers - passive equilibrium samplers of, e.g., silicone - as an integrative tool for the assessment of hydrophobic organic compounds in multimedia environments. The traditional way of assessing levels of organic pollutants across different environmental compartments is to compare the chemical concentration normalized to the major sorptive phase in two or more media. These sorptive phases for hydrophobic organic compounds differ between compartments, e.g., lipids in biota and organic carbon in sediments. Hence, comparability across media can suffer due to differences in sorptive capacities, but also extraction protocols and bioavailability. Chemometers overcome these drawbacks; they are a common, universal and well-defined polymer reference phase for sampling of a large range of nonpolar organic pollutants in different matrices like biota, sediment and water. When bringing the chemometer into direct contact with the sample, the chemicals partition between the sample and the polymer until thermodynamic equilibrium partitioning is established. At equilibrium, the chemical concentrations in the chemometers can be determined and directly compared between media, e.g., between organisms of different trophic levels or inhabiting different areas, between organs within an organism or between biotic and abiotic compartments, amongst others. Chemometers hence allow expressing the data on a common basis, as the equilibrium partitioning concentrations in the polymer, circumventing normalizations. The approach is based on chemical activity rather than total concentrations, and as such, gives a measure of the "effective concentration" of a compound or a mixture. Furthermore, chemical activity is the main driver for partitioning, biouptake and toxicity. As an additional benefit, the extracts of the chemometers only require limited cleanup efforts, avoiding introduction of a bias between chemicals of different persistence, and can be submitted to both chemical analysis and/or bioanalytical profiling.

Polyvinyl Alcohol/Pectin-Based Hydrogel as Sorptive Phase for the Determination of Freely Dissolved Parabens in Urine Samples by LC-DAD

An extraction phase based on hydrogel disks of polyvinyl alcohol and pectin was developed, characterized, and evaluated for the extraction of four endocrine disruptors (methylparaben, ethylparaben, propylparaben and butylparaben) in free form in human urine samples with subsequent determination by liquid chromatography coupled with a diode array detector (LC-DAD). The proposed hydrogel showed easy synthesis, was made of low-cost and non-toxic polymers, and showed that it has an amphiphilic character. Gels with lower swelling indexes (175%) and more concentrated dispersions of polymers (P20PC2.0) showed lower relative standard deviation (RSD) values. Under optimized solid phase extraction (SPE) conditions, the LC-DAD method presented limits of quantification of 0.1 µg mL-1, accuracy values ranged from 101.3 to 118.2%, while the inter-assay precision ranged from 1.5 to 17.4%. In addition, the polyvinyl alcohol (PVOH)/pectin-based material presented the possibility of reuse of at least 15 times, without presenting carryover effect and physical degradation. In this way, the hydrogel shows promise for the extraction of organic compounds with different polarities in biological matrices.