A novel approach to bar adsorptive microextraction: Cork as extractor phase for determination of benzophenone, triclocarban and parabens in aqueous samples

Simultaneous and sensitive detection of methylparaben and its metabolites by using molecularly imprinted solid-phase microextraction fiber array technique

BACKGROUND

Methylparaben (MP), a commonly used antibacterial preservative, is widely used in personal care products, foods, and pharmaceuticals. MP and its metabolites are easy to enter the water environment, and their exposure and accumulation have negative effects on the ecological environment and human health, and have endocrine disrupting activity and potential physiological toxicity. It is still the primary issue of environmental analysis and ecological risk assessment to develop simple and reliable methods for simultaneous sensitive detection of these compounds in environmental water.

RESULTS

In this paper, a flexible molecularly imprinted fiber array strategy is proposed for simultaneous enrichment and detection of trace MP and its four main metabolites. The experimental results showed that the three-fiber imprinted fiber array constructed by MP imprinted fiber had the best effect on the simultaneous enrichment of these five target analytes. The enrichment capacity of the imprinted fiber array was 214-456 times, 314-1201 times and 38-685 times that of commercial PA, PDMS and PDMS/DVB fiber arrays, respectively. The limit of detection (LOD) of this method was 0.033 μg L-1. The spiked recovery rate was 86.78-113.96 %, and RSD was less than 9.17 %. In addition, this molecularly imprinted SPME fiber array has good stability, long service life and can be used repeatedly at least 100 times.

SIGNIFICANCE

This molecularly imprinted fiber array strategy can flexibly assemble different molecularly imprinted SPME fibers together, effectively improve the enrichment ability and detection sensitivity, and achieve simultaneous selective enrichment and detection of several analytes. This is an easy, efficient and reliable method for monitoring several trace analytes simultaneously in intricate environmental matrices.

Benzophenones in the Environment: Occurrence, Fate and Sample Preparation in the Analysis

The ubiquitous presence of emerging contaminants in the environment is an issue of great concern. Notably, for some of them, no established regulation exists. Benzophenones are listed as emerging contaminants, which have been identified in the environment as well as in human fluids, such as urine, placenta, and breast milk. Their accumulation and stability in the environment, combined with the revealed adverse effects on ecosystems including endocrine, reproductive, and other disorders, have triggered significant interest for research. Benzophenones should be extracted from environmental samples and determined for environmental-monitoring purposes to assess their presence and possible dangers. Numerous sample preparation methods for benzophenones in environmental matrices and industrial effluents have been proposed and their detection in more complex matrices, such as fish and sludges, has also been reported. These methods range from classical to more state-of-the-art methods, such as solid-phase extraction, dispersive SPE, LLE, SBSE, etc., and the analysis is mostly completed with liquid chromatography, using several detection modes. This review critically outlines sample preparation methods that have been proposed to date, for the extraction of benzophenones from simple and complex environmental matrices and for cleaning up sample extracts to eliminate potential interfering components that coexist therein. Moreover, it provides a brief overview of their occurrence, fate, and toxicity.

Application of Response Surface Methodology to Optimize Solid-Phase Extraction of Benzoic Acid and Sorbic Acid from Food Drinks

An experimental design was applied for the optimization of the extraction process of two preservatives, benzoic and sorbic acids (BA, SA), from food drinks. A simple, rapid, and reliable solid-phase extraction (SPE) method for the simultaneous extraction of these two preservatives and their determination by liquid chromatography with a diode array detector was considered. Box−Behnken design (BBD) was applied to both steps of the SPE process: (i) the sample percolation to ensure the retention of the totality of the acids by the silica-based C18 sorbent; (ii) the elution step to ensure desorption of the totality of the acids from the cartridge. Thus, the volume, pH, and flow rate of the sample, and the percentage of MeOH, volume, and flow rate of the elution solvent, were optimized. Sample volume and pH have a significant influence (p < 0.0001 and p = 0.0115) on the percolation yield. However, no effect was recorded for the flow rate (p > 0.05). Flow rate also has no significant effect on the elution efficiency. The proposed new solid-phase extraction method, which can be easily applied to routine monitoring of preservatives BA and SA in juice and soft drink samples, included 0.5 g of C18 sorbent, 1 mL of food drink adjusted to pH 1 and percolated at 4.5 mL min−1, and 1 mL of a solvent mixture composed of methanol/acidified water (pH = 2.6) (90:10, v/v) used in the elution step at a flow rate of 4.5 mL min−1. Validation of the SPE method and the technique of analysis were evaluated, namely, the accuracy, precision, detection, and quantification limits and linearity. Recovery percentages of benzoic and sorbic acids were above 95% with relative standard deviations lower than 1.78%. Detection and quantification limits were 0.177 and 0.592 µg mL−1, and 0.502 and 0.873 µg mL−1 for benzoic acid and sorbic acid respectively. Optimal conditions were applied to commercial fruit juices and soft drinks and a minimal matrix effect was observed. This method was compared with other SPE methods using oxidized activated carbon and multiwalled carbon nanotubes as adsorbents. The yields determined with these last two were low compared to those determined with our method.

Wooden-based materials: Eco-friendly materials for direct mass spectrometric analysis and microextraction

Lignocellulosic materials have arisen as a sustainable alternative in microextraction techniques during the last 10 years. As they are natural materials, their use fits into some of the principles of Green Analytical Chemistry. Their inherent porosity, narrow shape, and rigidity permit their use in ambient ionization mass spectrometry techniques. In particular, the combination of wooden-based materials and direct analysis gives birth to the so-called wooden-tip electrospray ionization mass spectrometry technique. This approach has been used for the direct analysis of complex samples, and as a streamlined tool for fingerprint quality analysis. Also, wooden-based materials can be superficially modified to boost the interaction with target compounds, allowing their isolation from complex samples. This review describes the potential and applicability of direct analysis using lignocellulosic materials, as well as other alternatives related to their use in microextraction.

Application of Bar Adsorptive Microextraction for the Determination of Levels of Tricyclic Antidepressants in Urine Samples

This work entailed the development, optimization, validation, and application of a novel analytical approach, using the bar adsorptive microextraction technique (BAμE), for the determination of the six most common tricyclic antidepressants (TCAs; amitriptyline, mianserin, trimipramine, imipramine, mirtazapine and dosulepin) in urine matrices. To achieve this goal, we employed, for the first time, new generation microextraction devices coated with convenient sorbent phases, polymers and novel activated carbons prepared from biomaterial waste, in combination with large-volume-injection gas chromatography-mass spectrometry operating in selected-ion monitoring mode (LVI-GC-MS(SIM)). Preliminary assays on sorbent coatings, showed that the polymeric phases present a much more effective performance, as the tested biosorbents exhibited low efficiency for application in microextraction techniques. By using BAμE coated with C18 polymer, under optimized experimental conditions, the detection limits achieved for the six TCAs ranged from 0.2 to 1.6 μg L-1 and, weighted linear regressions resulted in remarkable linearity (r2 > 0.9960) between 10.0 and 1000.0 μg L-1. The developed analytical methodology (BAμE(C18)/LVI-GC-MS(SIM)) provided suitable matrix effects (90.2-112.9%, RSD ≤ 13.9%), high recovery yields (92.3-111.5%, RSD ≤ 12.3%) and a remarkable overall process efficiency (ranging from 84.9% to 124.3%, RSD ≤ 13.9%). The developed and validated methodology was successfully applied for screening the six TCAs in real urine matrices. The proposed analytical methodology proved to be an eco-user-friendly approach to monitor trace levels of TCAs in complex urine matrices and an outstanding analytical alternative in comparison with other microextraction-based techniques.

Exploring the use of cork pellets in bar adsorptive microextraction for the determination of organochloride pesticides in water samples with gas chromatography/electron capture detection quantification

In this study, a biosorbent material with characteristics for the adsorption of organic compounds was used for a cork pellet-based bar adsorptive microextraction technique, as a new greener alternative for the determination of organochlorine compounds. Aldrin, chlordane, dieldrin, endrin, lindane, 4,4-DDD, 4,4-DDE, 4,4-DDT, α-endosulfan and β-endosulfan were analyzed in water samples (drinking water, stream water and river water) with separation/detection by gas chromatography and electron capture detection (GC/ECD). The parameters that can affect the sample preparation efficiency such as desorption solvent and time as well as extraction time and ionic strength were evaluated by multivariate and univariate designs. Cork pellets (10  ×  Ø 3 mm) were used for the extraction of 15 mL of sample in the optimal conditions: 60 min of agitation with no salt added to the sample, followed by desorption of the cork pellet with 120 µL of ethyl acetate for 30 min. The bar-to-bar RSD out with five different bars showed good results with RSD ≤ 15.6%, allowing the use of simultaneous extractions. LOD and LOQ values ranged from 3 to 15 ng L^-1 and 10 to 50 ng L^-1 respectively, and the determination coefficients were greater than 0.9869. The target analytes were not detected in the three analyzed samples. Therefore, the recovery study was performed fortifying the water samples. Analyte recovery ranged from 48.7 - 138.2% for drinking water, 40.2 - 128.2% for stream water and 67.5 - 128.7% for river water.

Low-cost disposable Poly(ethyleneimine)-Functionalized Carbon Nanofibers Coated Cellulose Paper as efficient solid phase extraction sorbent material for the extraction of Parahydroxybenzoates from environmental waters

Parahydroxybenzoates (parabens) are considered as emerging environmental contaminants because of their extensive usage in our daily life products, causing parabens contamination into environmental water systems and lead to toxic effects on environmental health. This study describes a greener extraction method using a new cationic polymer poly (ethyleneimine) functionalized acid-treated carbon nanofibers (PEI-CNFs) coated cellulose paper (CP) as solid-phase extraction (SPE) sorbent material for the extraction of parabens from environmental water samples. The fabrication of PEI-CNFs modified CP was confirmed using field-emission scanning electron microscope, transmission electron microscopy, and fourier-transformer infrared spectroscopy techniques. Various factors affecting the adsorption and desorption of parabens on PEI-CNFs@CP and its extraction efficiencies were studied using HPLC-UV analysis. Under the optimal experimental conditions, maximum extraction efficiencies were achieved for four target parabens, and PEI-CNFs@CP/HPLC-UV method exhibited excellent linearities ranged from 0.5-50 ng mL^-1 with regression coefficient values were between 0.9952-0.9970. The presented method showed good sensitivity with quantification limits between 0.5-0.75 ng mL^-1 and detection limits between 0.1-0.25 ng mL^-1. The developed technique was applied for the real sample analysis (river, lake, domestic sewage water, and drinking tap water). The spiked recovery revealed good recoveries between 86.8-116.0% with RSD less than 8.8% for all the water samples. These results proved that it a simple, fast, efficient, low-cost, and eco-friendly method for the extraction and determination of parabens in environmental water samples and can be applied as a routine analytical tool in environmental monitoring and quality control laboratories.

Bar adsorptive microextraction device coated with polyimide microsphere assembled by nanosheets combined with thermal desorption-gas chromatography for trace analysis of nitroaromatic explosives in environmental waters

Polyimide (PI) microspheres assembled by nanosheets were used for bar adsorptive microextraction (BAμE) for the first time. The PI microsphere possessed self-organized hierarchical nanostructure, large specific surface area (170 m²/g) and good thermostability (up to 400 °C). The BAμE device was prepared by adhering the PI microspheres on a quartz bar with Kapton double sided tape. Trace nitroaromatic explosives in environmental waters were extracted by the BAμE device, desorbed by thermal desorption (TD), and analyzed by gas chromatography-mass spectrometry (GC-MS). The reproducibility of five BAμE devices prepared in parallel was less than 13.0% (expressed as relative standard deviation, RSD). The BAμE device could stand up to 30 extraction/desorption cycles without decrease of extraction efficiency. The results of method validation showed that the BAμE-TD/GC-MS method possessed wide linearity (0.05-50 μg/L or 0.05-20 μg/L), high correlation coefficients (> 0.9987), good precision (RSDs < 11.8%), low detection limits (0.005-0.013 μg/L) and high enrichment factors (528-1410). Relative recoveries were in the range of 72.2-122.6% with RSDs between 0.1% and 10.5% for real water samples. These results proved that the proposed method was a good choice for determination of organic pollutants in water samples.

Rapid, sensitive and simultaneous determination of 16 endocrine-disrupting chemicals (parabens, benzophenones, bisphenols, and triclocarban) in human urine based on microextraction by packed sorbent combined with liquid chromatography tandem mass spectrometry (MEPS-LC-MS/MS)

A high demand exists in human biomonitoring studies for reliable and straightforward methods that generate data faster and simultaneously. Thus, the present study combines microextraction by packed sorbent (MEPS) and liquid chromatography coupled to mass spectrometry (LC-MS/MS) for simultaneous extraction and determination of various classes of endocrine-disrupting chemicals (EDCs), including parabens, benzophenones, bisphenols, and the antimicrobial, triclocarban in human urine samples. Optimized MEPS conditions were: i) MEPS sorbent (C18), ii) pH of sample (3), iii) volume of sample (250 μL), iv) number of draws-eject cycles (5) and (vi) desorption solvent conditions (100 μL of CH₃OH:H₂O 80:20 v/v). The calibration curves were linear over the selected ranges for all studied compound, with correlation coefficients higher than 0.99. The variation coefficient for precision was lower than 20% at lower concentrations and lower than 15% at the higher concentrations studied. The accuracy ranged from 90% to 118%. The proposed strategy affords several advantages over currently published approaches, including simplicity of operation and reduction of sample and solvent volumes and time for matrix clean-up. Moreover, the analytical performance of each MEPS cartridge remained stable over the analysis of at least 70 samples (RSD < 10%). Thus, the current procedure may be an interesting high-throughput alternative for large routine human biomonitoring studies. Urinary geometric mean concentrations of EDCs obtained in this study were close than those previously reported for Brazilian children.

Returning to Nature for the Design of Sorptive Phases in Solid-Phase Microextraction

Green analytical chemistry principles aim to minimize the negative impact of analytical procedures in the environment, which can be considered both at close (to ensure the safety of the analysts) and global (to conserve our natural resources) levels. These principles suggest, among other guidelines, the reduction/minimization of the sample treatment and the use of renewable sources when possible. The first aspect is largely fulfilled by microextraction, which is considered to be among the greenest sample treatment techniques. The second consideration is attainable if natural products are used as raw materials for the preparation of new extraction phases. This strategy is in line with the change in our production system, which is being gradually moved from a linear model (take–make–dispose) to a circular one (including reusing and recycling as key terms). This article reviews the potential of natural products as sorbents in extraction and microextraction techniques from the synergic perspectives of two research groups working on the topic. The article covers the use of unmodified natural materials and the modified ones (although the latter has a less green character) to draw a general picture of the usefulness of the materials.

Cork sheet as a sorptive phase to extract hormones from water by rotating-disk sorptive extraction (RDSE)

This work reports for the first time the use of laminar cork as a sorptive phase in a microextraction technique, rotating-disk sorptive extraction (RDSE). Typical hormones (estrone, estradiol, estriol and ethinyl estradiol) were selected as analyte models and extracted from wastewater samples on laminar cork with statistically equivalent extraction efficiency to that provided by Oasis HLB. The cork characterization was performed by confocal fluorescence microscopy (CLSM), Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM), allowing the identification of lignin, suberin and polysaccharides (cellulose and hemicellulose) as the main components of the cork. The best conditions for extraction were as follows: rotation velocity of the disk, 2000 rpm; extraction time, 45 min; and sample volume, 20 mL. The analytical features of the developed method show that calibration curves for all analytes have R² values higher than 0.99. The absolute recoveries were higher than 63%, and the precision, expressed as relative standard deviation, ranged from 2 to 16%. The LOD and LOQ ranges were 3-19 and 10-62 ng L^-1, respectively. The proposed method was applied to the analysis of wastewater, and the concentrations of hormones in a wastewater treatment plant in Santiago, Chile, ranged from <LOQ to 48 ng L^-1.

Alternative Green Extraction Phases Applied to Microextraction Techniques for Organic Compound Determination

The use of green extraction phases has gained much attention in different fields of study, including in sample preparation for the determination of organic compounds by chromatography techniques. Green extraction phases are considered as an alternative to conventional phases due to several advantages such as non-toxicity, biodegradability, low cost and ease of preparation. In addition, the use of greener extraction phases reinforces the environmentally-friendly features of microextraction techniques. Thus, this work presents a review about new materials that have been used in extraction phases applied to liquid and sorbent-based microextractions of organic compounds in different matrices.

Bract as a novel extraction phase in thin-film SPME combined with 96-well plate system for the high-throughput determination of estrogens in human urine by liquid chromatography coupled to fluorescence detection

In this study, an environmentally friendly and high-throughput method was developed for the determination of estrone (E1), 17β-estradiol (E2), 17α-ethinylestradiol (EE2) and estriol (E3) in human urine by liquid chromatography-fluorescence detector (HPLC-FLD). A biosorbent (bract) was proposed as extraction phase for Thin-Film SPME combined with 96-well system. The characterization of the biosorbent was performed by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The optimizations were carried out through univariate and multivariate approaches with optimal conditions comprised of urine samples diluted 40-fold, liquid desorption performed in methanol and addition of 20% (w/v) of NaCl in the sample. Considering an extraction/desorption cycle using the 96-well plate system, the sample preparation time was 1.7 min per sample, which contributes to the high-throughput of the method proposed. The analytical parameters of merit were determined and satisfactory results were achieved, including limits of detection ranging from 0.3 μg L^-1 for estradiol to 3 μg L^-1 for estrone, while limits of quantification varied from 1 μg L^-1 for estradiol to 10 μg L^-1 for estrone. The correlation coefficients ranged from 0.9947 for estrone to 0.9999 for estriol. The accuracy and intra-assay and intermediate precisions (RSD) were evaluated through extractions in diluted urine samples (40-fold) spiked with each analyte (1, 200 and 400 μg L^-1 for E3; 0.1, 200 and 400 μg L^-1 for E2; 0.5, 200 and 400 μg L^-1 for EE2 and 10, 200 and 400 μg L^-1 for E1). The relative recoveries (n = 3) ranged from 71 to 105%, intra-assay precision (n = 3) varied from 1 to 17% and intermediate precision (n = 9) ranged from 2 to 19%. The method developed can be successfully used for the quantification of estrogens in human urine samples.

Preparation of macroscopic carbon nanohorn-based monoliths in polypropylene tips by medium internal phase emulsion for the determination of parabens in urine samples

A porous monolithic solid based on single-walled carbon nanohorns dahlia-like structure, produced from a medium internal phase emulsion (MIPE), was prepared in a polypropylene tip using UV energy. Thus, single-walled carbon nanohorns (SWNHs) were added to the organic phase where they polymerized in the presence of a radical initiator. A cross-linker (ethylene dimethacrylate, EDMA) was also used in order to obtain a more robust structure. On the other hand, aqueous phase was the responsible for generating the pores in the final solid being inside the droplets generated by the surfactant (Pluronic L121) used to stabilize the polymerization emulsion. Variables related to the formation of the monolithic phase including the stability and composition of emulsion mixture, size of pores, solvent flow resistance and robustness, were studied in detail. In addition, the potential of the SWNH-monolith as extractant phase was evaluated using parabens as target analytes. The LODs ranged from 1 to 7 μg L^-1, while the linear range was extended up to 5000 μg L^-1. The reproducibility of the extraction procedure with different batches of emulsions was acceptable with RSD values < 16% and one prepared SWNH-tip can be used for more than 100 times without apparent extraction losses. The microextraction unit yielded an enrichment factor of 20 for all analytes (extraction efficiency of 100%), with recovery values between 80% and 116% in human urine samples.

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.

Low-cost approach to increase the analysis throughput of bar adsorptive microextraction (BAµE) combined with environmentally-friendly renewable sorbent phase of recycled diatomaceous earth

In this study, a novel apparatus for bar adsorptive microextraction (BAµE) using a voltage regulator was proposed as an alternative tool to improve the analysis throughput. In addition, recycled diatomaceous earth obtained as a brewery residue was employed as a biosorbent coating for the determination of methyl paraben, ethyl paraben, benzophenone and triclocarban in water samples by high-performance liquid chromatography-diode array detection (HPLC-DAD). The use of the extraction devices, comprised of floating adsorptive bars of 7.5mm length, in the extractions with magnetic stirrers linked to a voltage regulator enabled the analysis of multiple samples, simultaneously. The method optimization was carried out by univariate and multivariate analyses. The optimal conditions for the method were sample solution at pH 5, extraction time of 90min and liquid desorption in 100µL of acetonitrile:methanol (50:50, v/v) for 15min. The total sample preparation time was 17.5min per sample for a simultaneous batch of six extractions. The R² values for the calibration curves obtained were higher than 0.9985. The limits of detection (LODs) varied from 0.19 to 2μgL^-1 and the limits of quantification (LOQs) ranged from 0.63 to 6.9μgL^-1. The method was applied to freshwater samples collected from Peri Lagoon (Florianópolis, SC, Brazil) and the relative recoveries ranged from 63% to 124% with relative standard deviations (RSDs) of < 20% (n = 2). The RSD values for the reproducibility of the performance of the magnetic stirrers and inter-device extraction efficiency were lower than 14% (n = 3) and 11% (n = 3), respectively.

A new configuration for bar adsorptive microextraction (BAμE) for the quantification of biomarkers (hexanal and heptanal) in human urine by HPLC providing an alternative for early lung cancer diagnosis

In this paper, a remodeling of the bar adsorptive microextraction (BAμE) technique is proposed with impregnation of the derivatization reagent on the surface of the adsorptive bar containing a biosorbent material. The derivatization reagent was 2,4-dinitrophenylhydrazine (DNPH), which was adsorbed on the surface of the bar containing cork powder as the extractor phase for the determination of two aldehydes (hexanal and heptanal) which are known as lung cancer biomarkers in human urine samples. The derivatization reaction and the extraction occurred simultaneously on the surface of the bar (length 7.5 mm) under acidic conditions. The method optimization was carried out by univariate and multivariate analysis. The optimal conditions for the method were a DNPH to aldehydes ratio of 40:1, buffer solution of pH 4.0, extraction time of 60 min and liquid desorption of 10 min in 100 μL of acetonitrile. The aldehydes were analyzed by HPLC-DAD with a simple and fast (6 min) chromatographic run. The limits of detection (LODs) for hexanal and heptanal were 1.00 and 0.73 μmol L^-1, respectively. The relative recoveries in urine samples ranged from 88 to 111% with relative standard deviations (RSDs) being less than 7%. The method developed is of low cost and can be successfully used for the quantification of these two lung cancer biomarkers in human urine samples, potentially providing an early diagnosis of lung cancer.