Advanced nanofibrous sorbents for the extraction of pollutants from river water and protein-containing matrices.

The extraction efficiencies of thirty types of fibers produced by meltblown, alternating current electrospinning, and meltblown-co-electrospinning technologies were tested as advanced sorbents for on-line solid-phase extraction in a high-performance liquid chromatography system have been tested and compared with a commercial C18 sorbent. The properties of each fiber, which were often depended on the production process, and their applicability were demonstrated with the extraction of the model analytes nitrophenols and chlorophenols from various matrices including river water and to purify complex matrix human serum and bovine serum albumin from macromolecular ballast. Polycaprolactone fibers outperformed other polymers and were selected for subsequent modifications including (i) incorporation of hybrid carbon nanoparticles, i.e., graphene, activated carbon, and carbon black into the polymer prior to fiber fabrication, and (ii) surface modification by dip coating with polyhydroxy modifiers including graphene oxide, tannin, dopamine, hesperidin, and heparin. These novel fibrous sorbents were comparable to commercial C18 sorbent and provided excellent analyte recoveries of 70-112% even from the protein-containing matrices.

Comparative study of drug release from electrospun nanofibers loaded with clotrimazole via two different approaches using a fully automated sequential injection system.

The development of new drug delivery platforms including the use of nanotechnology has been found of great interest in recent years. Two different loading approaches of the model antimycotic drug clotrimazole into the nanofibrous polycaprolactone and polydioxanone structures including electrospinning of a drug-polymer blend and impregnation of nanofibers with drug have been tested. The final amount of clotrimazole in the nanofibrous materials was determined by HPLC analysis and Raman spectroscopy. The electrospinning of blend approach allowed the adsorption of clotrimazole in a quantity of up to 30 % using mixtures with polymer/clotrimazole ratios from 2:1 to 8:1 (w/w). Ethanolic clotrimazole solutions with concentrations from 2.5 to 3.5 mg L-1 were used for adsorbing clotrimazole in blank nanofibers for 1-3 h with final clotrimazole content ranging from 3.0 to 5.7 %. Furthermore, a comparative liberation study including comparison with commercially available creams was carried out in low pressure flow system. The results obtained confirmed well controlled release of clotrimazole from both types of nanofibers. Compared to commercial pharmaceutical formulations containing 1 % clotrimazole where first-order release kinetics was observed, nanofibrous materials provided linear controlled release (zero-order kinetics) in the tested 3 h period.

Large-Scale Development of Antibacterial Scaffolds: Gentamicin Sulfate-Loaded Biodegradable Nanofibers for Gastrointestinal Applications.

The ever-increasing demands of modern medicine drive the development of novel drug delivery materials. In particular, nanofibers are promising for such materials due to their favorable properties. However, most development is still carried out through laboratory techniques that do not allow extensive and reproducible characterization of materials, which slows medical research. In this work, we focus on the large-scale fabrication and testing of specific antibacterial nanofibrous materials to prevent the postoperative complications associated with the occurrence of bacterial infection. Poly-ε-caprolactone with gentamicin sulfate (antibiotic) in different concentrations was electrospun via a needleless device. The amount of antibiotics was proven by elemental analysis, UV spectrophotometry, and HPLC. The cytocompatibility of the materials was verified in vitro according to ISO 10993-5. The cell adhesion and proliferation were assessed after 2, 7, 14, and 21 days using the CCK-8 metabolic assay, fluorescence, and scanning electron microscopy. The tested nanofiber materials supported cell growth. Antibacterial tests were performed to confirm the release of gentamicin sulfate, and its antibacterial properties were proven toward Staphylococcus gallinarum and Escherichia coli bacteria. The effect of ethylene oxide sterilization was also studied. The sterilized nanofibrous layers are cytocompatible while antibacterial and therefore suitable for medical applications.

Longevity and other practical benefits of monolithic silica columns in the analysis of samples with complex matrices.

At the turn of the millennium, the monolithic columns invoked new chances in HPLC. Even more than their organic polymer-based siblings, the inorganic silica-based monoliths targeted the territory of classical fully porous particle-packed columns, promising many benefits. Based on the number of published articles, the monoliths attracted academics just in the first few years after their introduction to the market. Lately, as superficially porous particles and sub-2-micron fully porous particles dominated the market, they stayed in the focus of routine laboratories and those who really appreciated the high porosity of the monolithic bed. The monoliths' practical benefits cannot be easily traced in the literature when they gradually lose academics' interest. Nevertheless, after more than 20 years of our experience, we still favor silica monoliths for their low back pressure and longevity when analyzing samples of clinical, pharmaceutical, and environmental origin. At the same time, the high permeability of monoliths enabled the birth of sequential injection chromatography, the medium-pressure separation technique based on the flexible flow manifold. This minireview aims to check, discuss, and summarize the practical aspects of monolithic silica columns in HPLC and medium-pressure sequential injection chromatography (SIC) that may not be visible at first sight but are evident retrospectively.

Small nanofibrous disks for preconcentration of environmental contaminants followed by direct in-vial elution and chromatographic determination.

A novel method for the extraction of river water contaminants as model analytes of ranging polarities, including bisphenols A, C, S, Z, fenoxycarb, kadethrin, and deltamethrin, using small compact fibrous disks has been developed and validated. Polymer nanofibers and microfibers prepared from poly(3-hydroxybutyrate), polypropylene, polyurethane, polyacrylonitrile, poly(lactic acid), and polycaprolactone doped with graphene were evaluated in terms of extraction efficiency, selectivity, and stability in organic solutions. Our novel extraction procedure comprised preconcentration of analytes from 150 mL river water to 1 mL of eluent using a compact nanofibrous disk freely vortexed in the sample. Small nanofibrous disks with a diameter of 10 mm were cut from a compact and mechanically stable 1-2 mm thick micro/nanofibrous sheet. After 60 min extraction in a magnetically stirred sample located in a beaker, the disk was removed from the liquid and washed with water. Then, the disk was inserted into a 1.5 mL HPLC vial and extracted with 1.0 ml methanol upon short intensive shaking. Our approach avoided the undesired problems related to the manual handling typical of "classical" SPE procedure since the extraction was carried out directly in the HPLC vial. No sample evaporation, reconstitution, or pipetting was required. The nanofibrous disk is affordable, needs no support or holder, and its use avoids creation of plastic waste originating from disposable materials. Recovery of compounds from the disks was 47.2-141.4% depending on the type of polymer used and the relative standard deviations calculated from 5 extractions ranged from 6.1 to 11.8% for poly(3-hydroxybutyrate), 6.3-14.8% for polyurethane, and 1.7-16.2% for polycaprolactone doped with graphene. A small enrichment factor was obtained for polar bisphenol S using all sorbents. A higher preconcentration reaching up to 40-fold was achieved for lipophilic compounds such as deltamethrin when using poly(3-hydroxybutyrate) and graphene-doped polycaprolactone.

Comparing adsorption performance of microfibers and nanofibers with commercial molecularly imprinted polymers and restricted access media for extraction of bisphenols from milk coupled with liquid chromatography.

Advanced solid phase extraction (SPE) fibrous sorbents including polyethylene, polypropylene poly (hydroxybutyrate), and polyamide 6 nanofibers, polycaprolactone microfibers/nanofibers, polycaprolactone microfibers/polyvinylidene difluoride nanofibers, and poly (hydroxybutyrate) microfibers/polypropylene microfibers composites, as well as commercial molecularly imprinted polymers and restricted access media sorbent were compared in terms of bisphenols extraction from milk and their clean-up efficiency. Three on-line SPE-HPLC methods were completely validated for the extraction and detection of bisphenols A, AF, C, A diglycidyl ether, and F diglycidyl ether in bovine milk. Polycaprolactone composite nanofibers compared favorably to restricted access media, enabled excellent clean-up of bisphenols from the proteinaceous matrix, and yielded recoveries 98.0-124.5% and 93.0-115.0%, respectively, with RSD less than 10%. Total analysis time including on-line SPE step lasted only 12 min, which represents a significant reduction in time compared with previously reported as well as official European Union and AOAC methods defined for the determination of bisphenols in various matrices.

Nanofibrous Online Solid-Phase Extraction Coupled with Liquid Chromatography for the Determination of Neonicotinoid Pesticides in River Waters.

Polymeric nano- and microfibers were tested as potential sorbents for the extraction of five neonicotinoids from natural waters. Nanofibrous mats were prepared from polycaprolactone, polyvinylidene fluoride, polystyrene, polyamide 6, polyacrylonitrile, and polyimide, as well as microfibers of polyethylene, a polycaprolactone nano- and microfiber conjugate, and polycaprolactone microfibers combined with polyvinylidene fluoride nanofibers. Polyimide nanofibers were selected as the most suitable sorbent for these analytes and the matrix. A Lab-In-Syringe system enabled automated preconcentration via online SPE of large sample volumes at low pressure with analyte separation by HPLC. Several mat layers were housed in a solvent filter holder integrated into the injection loop of an HPLC system. After loading 2 mL sample on the sorbent, the mobile phase eluted the retained analytes onto the chromatographic column. Extraction efficiencies of 68.8-83.4% were achieved. Large preconcentration factors ranging from 70 to 82 allowed reaching LOD and LOQ values of 0.4 to 1.7 and 1.2 to 5.5 µg·L-1, respectively. Analyte recoveries from spiked river waters ranged from 53.8% to 113.3% at the 5 µg·L-1 level and from 62.8% to 119.8% at the 20 µg·L-1 level. The developed methodology proved suitable for the determination of thiamethoxam, clothianidin, imidacloprid, and thiacloprid, whereas matrix peak overlapping inhibited quantification of acetamiprid.

Determination of Phloridzin and Other Phenolic Compounds in Apple Tree Leaves, Bark, and Buds Using Liquid Chromatography with Multilayered Column Technology and Evaluation of the Total Antioxidant Activity.

Apples are known to be a rich source of phenolic compounds, however detailed studies about their content in the individual parts of apple trees are reported rarely. For this purpose, we tested various stationary phases for the determination of phenolic compounds in leaves, bark, and buds. Phloridzin, phloretin, chlorogenic acid, rutin, and quercitrin were analyzed with high performance liquid chromatography coupled with diode array detection. A YMC Triart C18-ExRS 150 × 4.6 mm, 5 µm particle size analytical column with multilayered particle technology was used. The separation was performed with a mobile phase that consisted of acetonitrile and 0.1% phosphoric acid, according to the gradient program, at a flow rate of 1 mL/min for 12.50 min. The concentration of phenolic compounds from 13 cultivars was in the range of 64.89-106.01 mg/g of dry weight (DW) in leaves, 70.81-113.18 mg/g DW in bark, and 100.68-139.61 mg/g DW in buds. Phloridzin was a major compound. The total antioxidant activity was measured using flow analysis and the correlation with the total amount of phenolic compounds was found. This finding can lead to the re-use of apple tree material to isolate substances that can be utilized in the food, pharmaceutical, or cosmetics industries.

UHPLC coupled with charged aerosol detector for rapid separation of steviol glycosides in commercial sweeteners and extract of Stevia rebaudiana.

Natural sweeteners are in high demand as a part of a healthy lifestyle. Among them, sweeteners with decreased caloric value and suitability for diabetes patients are most requested. Extension in their consumption extends the need for their quality control. A fast gradient UHPLC coupled with charged aerosol detection enabling quantitation of stevioside, rebaudioside A-D, and steviolbioside in commercial sweeteners and Stevia rebaudiana plant extracts has been developed. The method was developed to achieve high efficiency, simplicity, versatility, and low solvent consumption. All steviol glycosides were baseline-separated in less than 4 min with a total run time of 7 min. Buffer-free eluents were used in the separations and only 2.45 mL solvent were needed per analysis. The Luna Omega Polar column featuring polar modification of the C18 stationary phase was employed with mobile phases composed of water and acetonitrile for the excellent separation of polar steviol glycosides. The flow rate of the mobile phase 0.35 mL/min, column temperature 50 °C and injection volume 2 µL were used. Critical pair of glycosides, stevioside and rebaudioside A, were baseline separated with a resolution of 2.41. The universal charged aerosol detector allowed quantitation of steviol glycosides with a limit of detection and quantitation 0.15 and 0.5 µg/mL, respectively. Method intra-day precision was less than 2% (RSD), and the recovery was 89.6-105.0% and 93.8-111.4% for plant material and sweetener tablets, respectively. The quantity of steviol glycosides in three out of four commercial sweeteners was 3.0-12.3% higher than declared. The content was about 12.4% less than declared in one sample. But the difference from the labeled content corresponded to trueness and precision of the developed method together with variability of sweeteners production. The most abundant glycoside detected in sweeteners was stevioside followed by rebaudioside A. A leaf-to-stem ratio describing the dominant accumulation of steviol glycosides in leaves affected the differences in the amount of steviol glycosides among plant samples.

Polycaprolactone Composite Micro/Nanofibrous Material as an Alternative to Restricted Access Media for Direct Extraction and Separation of Non-Steroidal Anti-Inflammatory Drugs from Human Serum Using Column-Switching Chromatography.

Application of the poly-ɛ-caprolactone composite sorbent consisting of the micro- and nanometer fibers for the on-line extraction of non-steroidal anti-inflammatory drugs from a biological matrix has been introduced. A 100 µL human serum sample spiked with ketoprofen, naproxen, sodium diclofenac, and indomethacin was directly injected in the extraction cartridge filled with the poly-ɛ-caprolactone composite sorbent. This cartridge was coupled with a chromatographic instrument via a six-port switching valve allowing the analyte extraction and separation within a single analytical run. The 1.5 min long extraction step isolated the analytes from the proteinaceous matrix was followed by their 13 min HPLC separation using Ascentis Express RP-Amide (100 × 4.6 mm, 5 µm) column. The recovery of all analytes from human serum tested at three concentration levels ranged from 70.1% to 118.7%. The matrix calibrations were carried out in the range 50 to 20,000 ng mL-1 with correlation coefficients exceeding 0.996. The detection limit was 15 ng mL-1, and the limit of quantification corresponded to 50 ng mL-1. The developed method was validated and successfully applied for the sodium diclofenac determination in real patient serum. Our study confirmed the ability of the poly-ɛ-caprolactone composite sorbent to remove the proteins from the biological matrix, thus serving as an alternative to the application of restricted-access media.

Evaluation of Anthocyanin Profiles in Various Blackcurrant Cultivars over a Three-Year Period Using a Fast HPLC-DAD Method.

Anthocyanins are the most important polyphenolic substances contained in blackcurrant fruits. They are responsible for the various health benefits caused, in particular, by their high antioxidant activity. Anthocyanins derived from anthocyanidins cyanidin and delphinidin are typical for blackcurrant fruits, especially their rutinoside and glucoside forms. These four anthocyanins usually represent about 97-98% of total anthocyanins in blackcurrant fruits. In this study, we developed and validated a new HPLC-DAD method for rapid anthocyanin separation and determination in fifteen perspective blackcurrant cultivars ('Ruben', 'Ben Lomond', 'Ben Conan', 'Ceres', 'Moravia', 'Ometa', 'Lota', 'Fokus', 'Tenah', 'Sejanec', 'Consort', 'Triton', 'Ben Hope', 'Ben Gairn', and one gooseberry hybrid 'Josta'). Eight of them were monitored throughout the three-year experiment. The most represented anthocyanins in all monitored blackcurrant cultivars were delphinidin-3-rutinoside (36.7-63.6%), cyanidin-3-rutinoside (26.4-40.6%), delphinidin-3-glucoside (6.1-17.9%), and cyanidin-3-glucoside (1.3-9.9%). The individual anthocyanin proportion (%) in each cultivar was specific, and a similar profile was verified in a three-year period for eight available cultivars. Total anthocyanin content expressed as a sum of four major anthocyanins present in blackcurrants was compared with values expressed as the equivalent of cyanidin-3-glucoside, as many authors do. We revealed an underestimation of about 20% with the latter method. Cultivars with the highest average total anthocyanin content were 'Ben Gairn' (294.38 mg/100 g), 'Ceres' (281.31 mg/100 g), and 'Ometa' (269.09 mg/100 g).

Dynamics of Phloridzin and Related Compounds in Four Cultivars of Apple Trees during the Vegetation Period.

Apple trees (Malus domestica Borgh) are a rich source of dihydrochalcones, phenolic acids and flavonoids. Considering the increasing demand for these phytochemicals with health-benefitting properties, the objective of this study was to evaluate the profile of the main bioactive compounds-phloridzin, phloretin, chlorogenic acid and rutin-in apple tree bark, leaves, flower buds and twigs. The variety in the phenolic profiles of four apple tree cultivars was monitored during the vegetation period from March to September using chromatography analysis. Phloridzin, the major glycoside of interest, reached the highest values in the bark of all the tested cultivars in May (up to 91.7 ± 4.4 mg g-1 of the dried weight (DW), cv. 'Opal'). In the leaves, the highest levels of phloridzin were found in cv. 'Opal' in May (82.5 ± 22.0 mg g-1 of DW); in twigs, the highest levels were found in cv. 'Rozela' in September (52.4 ± 12.1 mg g-1 of DW). In the flower buds, the content of phloridzin was similar to that in the twigs. Aglycone phloretin was found only in the leaves in relatively low concentrations (max. value 2.8 ± 1.4 mg g-1 of DW). The highest values of rutin were found in the leaves of all the tested cultivars (10.5 ± 2.9 mg g-1 of DW, cv. 'Opal' in September); the concentrations in the bark and twigs were much lower. The highest content of chlorogenic acid was found in flower buds (3.3 ± 1.0 mg g-1 of DW, cv. 'Rozela'). Whole apple fruits harvested in September were rich in chlorogenic acid and phloridzin. The statistical evaluation by Scheffe's test confirmed the significant difference of cv. 'Rozela' from the other tested cultivars. In conclusion, apple tree bark, twigs, and leaves were found to be important renewable resources of bioactive phenolics, especially phloridzin and rutin. The simple availability of waste plant material can therefore be used as a rich source of phenolic compounds for cosmetics, nutraceuticals, and food supplement preparation.

The role of pKa, log P of analytes, and protein matrix in solid-phase extraction using native and coated nanofibrous and microfibrous polymers prepared via meltblowing and combined meltblowing/electrospinning technologies.

Effect of physicochemical properties including dissociation constant (pKa) and partition coefficient (log P) of the compounds on their extraction efficiency in sample preparation using fibrous polymer sorbents has been demonstrated. Poly-ε-caprolactone as meltblown/electrospun composite fibers, and polypropylene, polyethylene, poly(3-hydroxybutyrate), poly(lactic acid), and polyamide 6 in the meltblown fiber format were used as sorbents in solid-phase extraction. In addition, the polycaprolactone fibers were coated with dopamine, dopamine combined with heparin, and tannin, respectively, to modify their extraction properties. These fibers that were not yet used for extractions and the unique combination of sorbents and analytes significantly extends the scope of nanofibrous extraction. The extraction efficiency was determined using model pharmaceuticals including acetylsalicylic acid, moxonidine, metoprolol, propranolol, propafenone, diltiazem, atorvastatin, and amiodarone. These model compounds displayed the widest differences in both pKa and log P values. The extraction efficiency of some of the fibers reached 96.64%. Coating of polycaprolactone fibers with dopamine significantly improved extraction efficiency of slightly retained metoprolol while moxonidine was not retained on any sorbent. The fibrous sorbents were also tested for extraction of pharmaceuticals in bovine serum albumin and human serum, respectively, to demonstrate their capability to extract them from a complex protein-containing matrix. The clean-up efficiency of our fibers was compared with that of a commercial restricted access media (RAM) C-18 alkyl-diol silica column. Our technique is in accordance with the requirements of modern sample preparation techniques.

Benefits and Pitfalls of HPLC Coupled to Diode-Array, Charged Aerosol, and Coulometric Detections: Effect of Detection on Screening of Bioactive Compounds in Apples.

The new screening method for rapid evaluation of major phenolic compounds in apples has been developed. Suitability of coupling HPLC/UHPLC separation with the diode-array detection and universal charged aerosol detection with respect to the presence of interfering substances was tested. Characteristics of both detection techniques were compared and method linearity, limits of detection and quantitation, and selectivity of them determined. Student t-test based on slopes of calibration plots was applied for the detailed comparison. The diode-array detection provided the best results regarding sensitivity and selectivity of the developed method in terms of evaluation of phenolics profiles. The response of the charged aerosol detector was negatively affected by co-eluting substances during rapid-screening analyses. Coulometric detection was used for advanced characterization of extracts in terms of antioxidant content and strength to obtain more complex information concerning sample composition. This detection also allowed evaluation of unidentified compounds with antioxidant activity. HPLC/UHPLC separation using a combination of diode-array and coulometric detectors thus represented the best approach enabling quick, yet complex characterization of bioactive compounds in apples.

Determination of Ochratoxin A and Ochratoxin B in Archived Tokaj Wines (Vintage 1959-2017) Using On-Line Solid Phase Extraction Coupled to Liquid Chromatography.

According to the EU legislation, ochratoxin A contamination is controlled in wines. Tokaj wine is a special type of sweet wine produced from botrytized grapes infected by "noble rot" Botrytis cinerea. Although a high contamination was reported in sweet wines and noble rot grapes could be susceptible to coinfection with other fungi, including ochratoxigenic species, no screening of Tokaj wines for mycotoxin contamination has been carried out so far. Therefore, we developed an analytical method for the determination of ochratoxin A (OTA) and ochratoxin B (OTB) involving online SPE coupled to HPLC-FD using column switching to achieve the fast and sensitive control of mycotoxin contamination. The method was validated with recoveries ranging from 91.6% to 99.1% with an RSD less than 2%. The limits of quantification were 0.1 and 0.2 µg L-1 for OTA and OTB, respectively. The total analysis time of the online SPE-HPLC-FD method was a mere 6 min. This high throughput enables routine analysis. Finally, we carried out an extensive investigation of the ochratoxin contamination in 59 Slovak Tokaj wines of 1959-2017 vintage. Only a few positives were detected. The OTA content in most of the checked wines did not exceed the EU maximum tolerable limit of 2 µg L-1, indicating a good quality of winegrowing and storing.

Current analytical methods for the characterization of N-deacetylated hyaluronan: A critical review.

N-Deacetylated hyaluronan (daHA) has been widely investigated as a starting material to develop biomaterials with unique composition and performance. However, its structure elucidation remains a challenging task due to its polysaccharide nature. After the brief mention of its properties and preparation, this review critically evaluates different analytical methods and approaches to characterize this promising polysaccharide. A special attention is paid to the determination of the degree of deacetylation. Besides, the analysis of its molecular weight, primary structure, and deacetylation pattern is also described. The older procedures are compared with the advanced techniques to provide reliable description of daHA.

On-line polydopamine coating as a new way to functionalize polypropylene fiber sorbent for solid phase extraction.

Effective process, including a cartridge packing polypropylene fiber sorbent modified by following on-line polydopamine coating, for on-line solid phase extraction in 2D UHPLC system has been developed. Hydrophobic surface of mechanically stable polypropylene fibers was hydrophilized using an automated and reproducible in situ coating process to enable good wettability and effective extraction of polar compounds. Polymerization mixture consisting dopamine and TRIS buffer was circulated through the cartridge containing polypropylene fibers using a peristaltic pump to achieve polymerization. This process was optimized in terms of dopamine amount in the polymerization mixture, its flow rate, and polymerization time. Best results were obtained with 25 mL polymerization mixture containing 20 mg dopamine circulated through the cartridge at a flow rate of 2.07 mL min-1 for 60 min. Prepared cartridges were evaluated via measurement of the recovery and reproducibility using chlorogenic acid as a model compound. Overall reproducibility of our multistep process including eight cartridges in 2D UHPLC system, each measured in triplicate, was 3.61% (n = 24).

Nanofibers as advanced sorbents for on-line solid phase extraction in liquid chromatography: A tutorial.

Polymers in nanofiber format promise a great potential as sorbents for extraction techniques. This tutorial provides an overview of direct coupling of extraction techniques based on nanofibers to liquid chromatography. Arrangements of the fibers in conventional extraction cartridges are demonstrated. Selection of suitable nanomaterials according to their surface density, wettability, and mechanical stability is proposed and personal experience of the authors commented. Optimization of on-line extraction procedure, practical aspects, technical problems, pitfalls, pros, and cons of using nanofibers for extraction in high-pressure chromatography systems are also discussed and several examples presented. The following text comprehensively summarizes numerous reports that dealt with the topic. Future perspectives of advanced nanofiber materials and approaches that concern polymer fibers modifications are also included.

Poly-ε-caprolactone Nanofibrous Polymers: A Simple Alternative to Restricted Access Media for Extraction of Small Molecules from Biological Matrixes.

Poly-ε-caprolactone nanofibrous polymer has been used as an alternative to restricted access media for extraction of protein-containing biological samples and direct transfer in the chromatographic system. Three commercial cartridges differing in length and internal diameter have been manually packed with the composite material prepared from poly-ε-caprolactone nanofibers coated on poly-ε-caprolactone microfibrous scaffold and connected to the column-switching chromatographic system. Bovine milk and human serum (25 µL) spiked with a mixture of methyl-, ethyl-, propyl-, and butylparaben in a concentration range of 1-100 µg mL-1 were online extracted using the cartridge-containing fibers. Then, 5 and 20% (v/v) aqueous methanol was applied as the washing mobile phase. While the ballast protein macromolecules were quantitatively eluted from the nano/microfibrous composite sorbent, the parabens were retained. After the mobile phase was switched to a stronger one, these compounds were then eluted from the extraction sorbent, directed in the analytical column, and finally separated. An extraction efficiency of 86-101% for all parabens achieved using the optimum-sized cartridge and a repeatability of the extraction procedure of 0.06-1.95% RSD were obtained.

3D-Printed Magnetic Stirring Cages for Semidispersive Extraction of Bisphenols from Water Using Polymer Micro- and Nanofibers.

A magnetic stirring device allowing semidispersive solid phase extraction of eight bisphenols (A, AF, AP, C, BP, G, M, and Z) from river waters using polymer nano- and microfibers followed by HPLC with spectrophotometric detection has been developed and applied. About 50 mg of fibers was placed in a round, cage-like housing consisting of two identical 3D printed pieces that were locked together by a magnetic stirring bar. Magnetic stirring action of the cage devices enabled highly efficient interaction of the fibers housed inside with the aqueous samples and analyte transfer without risking fiber compaction and/or damaging. Polypropylene was found to be the best-suited filament material for the cage 3D printing, and polycaprolactone fibers appeared the most efficient sorbent out of eight tested polymers. Experimental design revealed that analytes extraction from 100 mL aqueous samples was completed within 50 min and stripping in methanol required less than 35 min. Cage housing enabled simple and robust handling of the fibrous sorbent that could be used repeatedly up to at least 5 times. Procedural repeatability was less than 5% RSD, and limits of detection and quantitation were 0.1-2.1 and 0.4-7.0 µg L-1, respectively. Analyte recoveries at 50 µg L-1 level ranged from 87.1% to 106.5% in the analysis of two spiked river and two lake waters.