Sorbent For Solid-phase Microextraction Research Articles

Multivariate surface self-assembly strategy to fabricate ionic covalent organic framework surface grafting monolithic sorbent for enrichment of aristolochic acids prior to high performance liquid chromatography analysis

Herein, an ionic covalent organic framework (iCOF) surface grafting monolithic sorbent was prepared by the multivariate surface self-assembly strategy for in-tube solid-phase microextraction (SPME) of trace aristolochic acids (AAs) in serum, traditional Chinese medicines (TCMs) and Chinese patent drug. Via adjusting the proportion of ionic COF building block during the self-assembly, the density of quaternary ammonium ions in the iCOF was modulated for the enhanced adsorption of AAs. The successful preparation of iCOF surface grafting monolithic sorbent was confirmed by different means. A multiple mode mechanism involving π-π stacking, hydrophobic, electrostatic and hydrogen-bonding interactions was primarily attributed to the adsorption. Several in-tube SPME operating conditions, such as the dosage of ionic COF building block, ACN percentage and TFA percentage in the sampling solution, ACN percentage and TFA percentage in eluent and the collection time span, were optimized to develop the online in-tube SPME-HPLC method for analysis of AAs. Under the optimized conditions, a good linearity was obtained in the concentration range of 20–1000 ng/mL for target AAs in serum samples, the limits of detection (LODs) were less than 10 ng/mL, while the recoveries ranged from 90.3 % to 98.7 % with RSDs (n = 5) below 7.9 %. This study developed a feasible approach to iCOF functionalized monolithic sorbent for SPME and further exhibited the vast potential for the application of COF based monolithic sorbent in sample preparation.

Batch Scale Production of 3D Printed Extraction Sorbents Using a Low-Cost Modification to a Desktop Printer.

This study reports a simple modification to a commercial resin 3D printer that significantly reduces the amount of prepolymer material needed for the production of extraction sorbents. The modified printing platform is demonstrated in the printing of two imidazolium-based ionic liquid (IL) monomers. Two geometries resembling a blade-type polymeric ionic liquid (PIL) sorbent used in thin-film microextraction and a fiber-type sorbent used in solid-phase microextraction (SPME) were printed. The SPME PIL sorbents were used to extract 10 organic contaminants, including plasticizers, antimicrobial agents, UV filters, and pesticides, from water followed by high-performance liquid chromatographic (HPLC) analysis. To compare the extraction performance of the SPME sorbents, seven fibers printed with the same prepolymer composition from the same printing batch as well as different batches were evaluated. The results revealed highly reproducible extraction efficiencies for all tested sorbents with no statistical difference in their extraction performance. Method validation showed acceptable linearity (R2 > 0.92) for all analytes with limits of detection and limits of quantification ranging from 0.13 to 45 μg L-1 and 0.43 to 150 μg L-1, respectively.

Nanoporous carbon fiber derived from Cu-BDC metal organic framework @pencil graphite as a sorbent for solid phase microextraction of acetamiprid and imidacloprid

Solid-phase microextraction (SPME) is a sample pretreatment technique for enrichment of trace level of compounds from complex matrices. The fiber coating, as an extraction phase, is the significant part of SPME, which specifying the analytical performance of the developed SPME. In this study, a novel in situ fabricated Cu@porous carbon fiber that derived from copper benzene-1,4-dicarboxylate framework@pencil graphite (Cu-BDC MOF@PG) fiber was prepared as a SPME fiber. The Cu-BDC MOF was electrodeposited on the surface of pencil graphite. The Cu@porous carbon fiber with nanoporous structure was constructed by the direct carbonization of the electrosynthesized fiber.The Cu@porous carbon fiber showed high analytical performance for direct immersion SPME (DI-SPME) of acetamiprid and imidacloprid in fruit and vegetable samples. The SPME method was coupled by high-performance liquid chromatography-ultraviolet detection (SPME-HPLC-UV) for determination of the analytes. Under the optimized condition, good linear ranges (1–500 μg L−1 and 0.5–200 μg L−1) and acceptable limits of detection (LODs = 0.30 and 0.15 μg L−1), appropriate spiking recoveries in the range 87–109.0% were attained for acetamiprid and imidacloprid, respectively. Intra- and inter-day relative standard deviations were found within the ranges of 2.35–3.46% and 3.30–3.70%, respectively. These results signify promising potential of the in situ fabricated porous carbon fiber for SPME applications.Considering that most of the pencil graphite is made of carbon, after the carbonization of the Cu-BDC MOF@PG fiber, a unified porous carbon fiber is obtained. Compared to other reported procedures, in situ direct carbonization of Cu-BDC MOF@PG fiber was a one-step and straightforward method to fabricate carbon fiber.

Polyoxometalate/reduced graphene oxide composite stabilized on the inner wall of a stainless steel tube as a sorbent for solid-phase microextraction of some parabens followed by quantification via high-performance liquid chromatography

An affordable high-throughput microextraction strategy is presented in the current study. Herein, polyoxometalate/reduced graphene oxide (POM/rGO) composite was prepared and after accommodation on the inner wall of the stainless steel tube, it was used to extract some of the selected parabens such as methyl paraben and propyl paraben from the real samples. The extracted model analytes were desorbed by a suitable organic solvent and quantified by high-performance liquid chromatography-ultraviolet detection (HPLC-UV). The uniform stabilization of POMs on the rGO sheets besides the hydrophobic interactions of rGO with the target analytes increase the extraction efficiency of method. The method validation tests were also performed. According to the obtained data, the linearity of the proposed method was in the range of 1.0–200.0 µg/L (0.2 µg/L < The limits of detection (LODs) < 0.3 µg/L and 0.6 µg/L < limits of quantification (LOQs) < 0.8 µg/L) for the selected parabens. The calibration curves showed the determination of coefficients higher than 0.9954. In order to calculate the precision of the method, the inter-day and intra-day relative standard deviations (RSDs %) were determined between 3.1 and 6.7 % in three concentrations. Furthermore, the enrichment factors were found to be 144 and 152 for methyl paraben and propyl paraben, respectively. Moreover, the calculated absolute recoveries were 72 and 76 % for methyl paraben and propyl paraben, respectively. The proposed method was also employed for the analysis of selected parabens in lipstick, blusher, emollient cream, toothpaste and shampoo. The obtained recoveries indicated that the method was applicable for the microextraction of methyl paraben and propyl paraben from cosmetic products without any interferences.

Ultrasound-assisted one-step reduction and self-assembly of carbon dots-reduced graphene oxide: Mechanism investigation and solid phase microextraction of ultra-trace organochlorine pesticides

In this work, carbon dots-reduction graphene oxide (CDs/RGO) composite was synthesized by a facile and green strategy with one-step reduction and self-assembly of GO and CDs under ultrasonic treatment. CDs was successfully applied to reduce GO to RGO, and anchored on the surface of RGO simultaneously under ultrasonic treatment within 20 min. The reduction mechanism was demonstrated by density functional theory calculations, which confirmed the electron transfer from CDs to GO and supplemented the reduction mechanism of GO by CDs. Characterizations results showed that the as-prepared CDs/RGO composite exhibited lamellar spacing and wrinkled structures, and abundant chemical groups in comparison to RGO reduced by sodium borohydride. In view of excellent morphology and chemical structures, the CDs/RGO composite was used for the first time in extraction and determination of ultra-trace organochlorine pesticides (OCPs) from water by means of solid phase microextraction (SPME) coupled with gas chromatography-mass spectrometry. The CDs/RGO coating presented superior extraction capacities for OCPs compared with commercial SPME coatings and sodium borohydride reduced RGO. The proposed analytical method exhibited high sensitivity with detection limit of 0.003–0.051 ng/L, excellent linearity in concentration range of 0.050–2500 ng/L, and satisfactory precision for seven OCPs. The excellent performances made the proposed method to be applied in determination of ultra-trace OCPs in real water successfully. This work proposed a green approach to synthesize CDs/RGO composite and a potential coating sorbent for SPME.

Recruiting chemical grafting method for surface modification of stainless steel to fabricate a selective sorbent for solid phase microextraction of mercury metal ion.

Keeping selectiveness and efficiency in view with solid-phase microextraction (SPME) of metal ions, this work was aimed at synthesis of a novel modified sorbent on a stainless-steel surface to fabricate a selective and efficient fiber for SPME of mercury ions from real food and biological samples. After the confirmation of sorbent structure grafted on the stainless-steel surface, by different techniques, the synthesized fiber was utilized for extraction and preconcentration of mercury before its measurement by an inductively coupled plasma-optical emission spectroscopy (ICP-OES). For optimizing the efficiency, the influences of various factors on the extraction of Hg (II) ion were scrutinized. The optimized values used for extraction were pH 7.0, adsorption time 8min, desorption time 5min, 5mL of eluent solvent containing nitric acid with concentration of 0.5mol L-1, and stirring rate of 300rpm. Underneath optimum condition, the relative standard deviation for 30 extractions, done by one synthesized fiber, was calculated to be 2.89% and for five extractions, done by 5 synthesized fibers, was calculated to be 1.78%. The high performance of the synthesized fiber was checked with high recoveries obtained from 30 successive sorption-desorption cycles, using a unique synthesized fiber. Finally, the suggested procedure was triumphally exploited for extraction and pre-concentration of Hg (II) ion in real food and biological samples.

Preparation of Molecular Imprinted Polymer Based on Chitosan as the Selective Sorbent for Solid-Phase Microextraction of Phenobarbital.

This study reports the construction of a novel SPME fiber based on chitosan and glutaraldehyde as coating material composites combined with high-performance liquid chromatography with an ultraviolet detector (HPLC-UV) for extraction and detection of phenobarbital. In this technique, the chitosan biopolymer, as a new coating of SPME fiber, was produced on the stainless-steel wire, using glutaraldehyde and phenobarbital as cross-linker and template, respectively. For comparison, a nonimprinted polymer was created using the same procedure to evaluate fiber selectivity (but without the addition of phenobarbital). The SPME-MIP fiber coating was characterized by field emission scanning electron microscopy, Fourier-transform infrared spectroscopy, and thermal gravimetric analysis. The efficiency of fiber was then improved by adjusting the impact of numerous factors such as pH, extraction time, desorption time, desorption solvent, and stirring rate. The results showed that the proposed fiber has a linear range of 0.01–4 μg·mL−1, and detection limit of 7.5 ng·mL−1. The average recoveries in the four concentration levels for the spiked river and well water samples were 95.7 and 95.3%, with relative standard deviations of 3.8 and 5.9% for single fiber and between fibers, respectively.

Selective Extraction of Trace Arsenite Ions Using a Highly Porous Aluminum Oxide Membrane with Ordered Nanopores.

Metal ion extraction and determination at trace level concentration are challenging due to sample complexity or spectral interferences. Herein, we prepared a through-hole aluminum oxide membrane (AOM) by electrochemical anodization of aluminum substrates. The prepared AOM was characterized by scanning electron microscopy, surface area analysis, porosity measurements, and X-ray photoelectron spectroscopy. The AOM with ordered nanopores was highly porous and possess inherent binding sites for selective arsenite sorption. The AOM was used as a novel sorbent for solid-phase microextraction and preconcentration of arsenite ions in water samples. The AOM’s sub-micrometer thickness allows water molecules to flow freely across the pores. Before instrumental determination, the suggested microextraction approach removes spectral interferents and improves the analyte ion concentration, with a detection limit of 0.02 μg L–1. Analyzing a standard reference material was used to validate the procedure. Student’s t-test value was less than critical Student’s t-value of 4.303 at a 95% confidence level. With coefficients of variation of 3.25%, good precision was achieved.

Molecularly imprinted dispersive solid-phase microextraction sorbents for direct and selective drug capture from the undiluted bovine serum

The preparation of well-defined new hydrophilic molecularly imprinted polymer (MIP) microspheres and their use as the dispersive solid-phase microextraction (dSPME) sorbents for direct and selective drug (i.e., propranolol) capture from the undiluted bovine serum are described. These MIPs have surface-grafted dense poly(2-hydroxyethyl methacrylate) (PHEMA) brushes with different molecular weights and grafting densities. They were readily prepared via the facile reversible addition-fragmentation chain transfer (RAFT) coupling chemistry. Both the molecular weights and grafting densities of PHEMA brushes showed significant influence on their complex biological sample-compatibility, and only those MIPs bearing PHEMA brushes with high enough molecular weights and grafting densities could selectively recognize propranolol in the undiluted pure milk and bovine serum. In particular, they have proven to be highly versatile dSPME sorbents for directly and selectively capturing propranolol from the undiluted bovine serum with satisfactory recoveries (85.2–97.4%) and high accuracy (RSD = 2.3–3.7%), even in the presence of one analogue of propranolol. The limit of detection was 0.002 μM with a linear correlation coefficient of 0.9994 in the range of 0.01–100 μM. Excellent precision was verified by both the intraday and interday analytical results. Their good reusability was also confirmed. This work demonstrates the high potential of such hydrophilic MIP-based dSPME sorbents for rapid, accurate, and reliable drug determination in complex biological samples.

Covalent triazine-based framework-grafted functionalized fibrous silica sphere as a solid-phase microextraction coating for simultaneous determination of fenthion and chlorpyrifos by ion mobility spectrometry.

A novel covalent triazine-based framework (CTF)-grafted phenyl-functionalized fibrous silica nanosphere, KCC-1 (named as RS-2) was synthesized via a simple and effective Friedel-Crafts approach. The microporous CTF with fluorene backbone was coupled and grown uniformly on the surface of phenyl-functionalized KCC-1 to prepare a hybrid extended porous framework. The prepared materialswere characterized, and FE-SEM and TEM images revealed a flower-like structure for RS-2. The synthesized RS-2 showed excellent thermal stability, so the weight loss was about 30% at 800°C. RS-2 was applied as a new coating in the solid-phase microextraction procedure to extract chlorpyrifos and fenthion pesticides fromwater, wastewater, and fruit samples, before determining by corona discharge-ion mobility spectrometry. Some experimental factors affecting the extraction yield of the analytes, including ionic strength, stirring rate, sample pH, extraction temperature, and extraction time, were investigated. Under optimum conditions, the linear dynamic ranges were 0.1-10μgL-1 and 1.0-70μgL-1, and the limits of detection were 0.05 and 0.55μgL-1 for chlorpyrifos and fenthion, respectively. The proposed method showed recovery values in the range 86-117% with a precision of 3.0-7.1% for real samples. Covalent triazine-based framework (CTF)-grafted phenyl-functionalized fibrous silica nanosphere (named as RS-2) was synthesized. RS-2 was applied as a sorbent for solid-phase microextraction (SPME) of chlorpyrifos and fenthion from fruit and water samples followed by corona discharge ionization ion mobility spectrometry (CD-IMS).

Application of biocharcoal aerogel sorbent for solid-phase microextraction of polycyclic aromatic hydrocarbons in water samples.

A facile method was introduced for preparing a biocharcoal aerogel, which was derived from pomelo peel as the only raw material. The inner spongy layer of pomelo peel was freeze-dried for maintaining three-dimensional structure and then carbonized under high temperature and oxygen-limited conditions. The morphological structure and graphitization degree of biocharcoal aerogel were characterized using a scanning electron microscope and Raman spectrum. After sifting and grinding, the biocharcoal aerogel as an adsorbent was coated onto the surface of stainless steel wires. Through placing the wires into a polyetheretherketone tube, the in-tube solid-phase microextraction device was obtained. Coupled with high-performance liquid chromatography, it exhibited good extraction performance for polycyclic aromatic hydrocarbons, then an online analytical method was established with low limits of detection (0.005-0.050ng/mL), wide linear ranges (0.017-15ng/mL) with superior correlation coefficients higher than 0.9990, high enrichment factors (1128-3425), and acceptable intra- and inter-day repeatabilities (relative standard deviations ≤ 6.7%, n=3). The method was applied to detect polycyclic aromatic hydrocarbons in bottled water samples, environmental water samples, and soft drinks with satisfactory recoveries (83.3-120.9%). This research not only developed a new carbon aerogel but also evaluated its adsorption performance in sample preparation.

Application of magnetic nanomaterials in magnetic in-tube solid-phase microextraction

Development of magnetic nanomaterials has greatly promoted the innovation of in-tube solid-phase microextraction. This review article gives an insight into recent advances in the modifications and applications of magnetic nanomaterials for in-tube solid-phase microextraction. Also, different magnetic nanomaterials which have recently been utilized as in-tube solid-phase microextraction sorbents are classified. This study shows that magnetic nanomaterials have gained significant attention owing to large specific surface area, selective absorption, and surface modification. Magnetic in-tube solid-phase microextraction has been applied for the analysis of food samples, biological, and environmental. However, for full development of magnetic in-tube SPME, effort is still needed to overcome limitations, such as mechanical stability, selectivity and low extraction efficiency. To achieve these objectives, research on magnetic in-tube SPME is mainly focused in the preparation of new extractive phases.

Development of an aptamer-functionalized capillary monolithic column for the highly-selective and highly-efficient recognition of patulin

Patulin is a type of mycotoxin that can compromise both food quality and human health, and its potential toxic effects on human health are concerning. Therefore, strict monitoring of patulin content in food systems is necessary. However, discrimination and quantification of this toxin are difficult because of its extremely low concentration at pg/g levels in food samples. A highly specific sample preparation method is, thus, vital for patulin analysis. Herein, we present an innovative approach for the facile and controllable preparation of an aptamer-functionalized capillary monolithic polymer hybrid for the determination of patulin in food samples with high specificity and high affinity by using the aptamer-functionalized monolithic capillary polymer hybrid as a sorbent for solid-phase microextraction (SPME) coupled with ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). The results confirmed that the developed SPME-UHPLC-MS/MS method was a sensitive and selective because of a low detection limit of 2.17 pmol/L and a linear range extending from 0.00811 to 8.11 nmol/L. Patulin was found to be present in apple juice samples (4.34 ng/kg). Furthermore, the recoveries were 85.4–106% with relative standard deviations (n = 5) of 4.1–7.3%. Thus, the highly selective method will facilitate the ultrasensitive detection of target molecules in diverse applications.

Application of the electropolymerized poly(3,4-ethylenedioxythiophene) sorbent for solid-phase microextraction of bisphenols.

A new, simple, and effective procedure using poly(3,4-ethylenedioxythiophene)/lignosulfonate electropolymerized sorbent solid-phase microextraction (PEDOT/LS-SPME) combined with LC-MS/MS for determination of bisphenols in environmental water samples was developed. Various parameters influencing the performance of the analytical procedure including the type of sorbent, electropolymerization time, sorbent preconditioning time, extraction time, desorption (time and solvent), and sample pH were investigated and optimized. Under optimal conditions the proposed method allowed us to achieve good precision (n = 5) between 6.0 and 12.1%. The limits of detection were equal to 0.17 μg L-1 for BPA, 0.16 μg L-1 for BPF, 0.07 μg L-1 for BPE, 0.05 μg L-1 for BPB, and 0.027 μg L-1 for BPAF. The proposed method was successfully applied for the determination of bisphenols in aqueous environmental samples.

Electrochemically prepared three-dimensional reduced graphene oxide-polyaniline nanocomposite as a solid-phase microextraction coating for ethion determination

Here, a three-dimensional reduced graphene oxide-polyaniline nanocomposite was synthesized and applied as a sorbent for solid-phase microextraction of ethion from water samples followed by negative corona discharge ionization ion mobility spectrometry. The nanocomposite was synthesized via a fast and facile two-step electrochemical method. The prepared sorbent was characterized by Fourier transform infrared spectroscopy, field emission scanning electron microscopy and thermogravimetric analysis. The main experimental parameters in the preparation of the fiber including concentration of graphene oxide, electrodeposition time, aniline concentration, and electropolymerization time were investigated. Also, parameters affecting the extraction process (i.e., salt addition, sample stirring rate, solution pH, extraction temperature and extraction time) were studied. Under the optimal conditions, the linearity and limit of detection were found to be 1.0–70 and 0.4 μg L−1, respectively. The method presented good precision (intra-day and inter-day, n = 3), ranged from 1.7 to 4.7%. The analyte recovery obtained using spiked real water samples were in the range of 84–98%.

Graphitic carbon nitride derivative with large mesopores as sorbent for solid-phase microextraction of polycyclic aromatic hydrocarbons

Although an efficient and stable fiber coating is essential for the development of the solid-phase microextraction (SPME) technique, it remains a challenging prospect. We report herein the construction of graphitic carbon nitride derivative (g–C3N4–d) nanosheets having a large surface area, large mesopores (3.15 and 36.6 nm), and abundant adsorption sites, and the application of coating g–C3N4–d on an SPME fiber. The coated SPME fiber combined with gas chromatography-mass spectrometry (GC-MS) was used for the determination of polycyclic aromatic hydrocarbons (PAHs). The coating contained large mesopores that accommodated large target molecules and promoted molecular diffusion inside the coating sorbent. The coating demonstrated significant extraction capability toward PAHs because of multiple interactions, including hydrophobic and strong π–π interactions. Under optimal conditions, the limits of detection for PAHs were achieved within the range of 0.01–0.10 ng L−1. The method developed to detect eight PAHs in six river water samples from different cities, and the recoveries were ranging from 83.3 to 103.0%. The g–C3N4–d nanosheet-coated fiber was sufficiently stable to be recycled more than 200 times without obvious loss of extraction capacity. This study describes the development of a novel SPME adsorbent having excellent analytical properties.

Direct molecular imprinting technique to synthesize coated electrospun nanofibers for selective solid-phase microextraction of chlorpyrifos.

Molecularly imprinted-electrospun nanofibers based on the use ofpoly(vinyl alcohol) were fabricated and used as a new sorbent for solid-phase microextraction of chlorpyrifos. The molecularly imprintednanofibers were prepared by electrospinning and direct molecular imprinting of polymeric nanofibers. Poly(vinyl alcohol) was used as the functional and electrospun polymer. Chlorpyrifos was used as a template molecule, and glutaraldehyde as the cross-linker. Detection was performed by ion mobility spectrometry equipped with a secondary electrospray ionization source. The molecularly imprinted fiber has a selectivity and extraction efficiency better than the fiber fabricated using the conventional method of encapsulating MIP particles in electrospun nanofibers. Parameters affecting the extraction efficiency such as ionic strength, stirring rate, extraction time, and temperature were evaluated. The dynamic range of the method was in the range of 0.5-200μgL-1 with the limit of detection of 0.1μgL-1. The intra- and inter-day relative standard deviations of the method were 4 and 9%, respectively. The fiber-to-fiber reproducibility for three different fibers is 5%. The spiking recoveries from spiked apple, cucumber, and water samples were in the range of 82-112%. Graphical abstract Molecularly imprinted-electrospun nanofibers were fabricated based on the direct molecular imprinting technique and used as a new SPME fiber coating for selective extraction of chlorpyrifos from fruits and water samples prior its determination by secondary electrospray ionization-ion mobility spectrometry.

Ordered macro/micro-porous metal-organic framework of type ZIF-8 in a steel fiber as a sorbent for solid-phase microextraction of BTEX.

An ordered array of macropores on microporous metal-organic framework crystals was developed. This array facilitates analyte diffusion in microextraction applications. A prototypical zeolitic imidazolate framework (ZIF-8) was synthesized in the interstitial voids of a polystyrene bead packing of sub-μm polystyrene beads. After removal of polystyrene by dimethylformamide, a single-crystal ordered macroporous ZIF-8 material (SOM-ZIF-8) was obtained. The resulting μm-sized SOM-ZIF-8 crystals are based on a fully-microporous structure containing a macroporous network. The SOM-ZIF-8 crystals were placed in a stainless-steel fiber and applied as a sorbent for the extraction of benzene, toluene, ethylbenzene, and xylenes (BTEX) by headspace solid-phase microextraction (HS-SPME). The fiber was applied to the HS-SPME of BTEX from wastewater samples followed by GC with flame ionization detection. A Plackett-Burman design and Box-Behnken design were carried out to evaluate the variables affecting the method. Figures of merit include (a) limits of detection of 1.0-12ng·L-1, (b) linear ranges of 0.004-50μg·L-1, (c) relative standard deviations of 4.6-6.7%, and (d) excellent fiber-to-fiber reproducibility (5.6-6.7% for n = 3). Spiking recoveries between 92 and 106% were obtained for BTEX analysis in wastewater samples. The introduction of an ordered macroporous network on microporous ZIF-8 crystals enhanced analyte uptake. This increases the extraction performance by a factor of 2.5-3.1 when compared to analogous ZIF-8 crystals that lack templated macropores. Graphical abstract BTEX extraction is enhanced by templating an ordered macroporous network in microporous crystals as exemplified with the single-crystal ordered macropore zeolitic imidazolate framework-8 (SOM-ZIF-8). Graphical Abstract contains poor quality of image inside the artwork. Please do not re-use the file that we have rejected or attempt to increase its resolution and re-save. It is originally poor, therefore, increasing the resolution will not solve the quality problem. We suggest that you provide us the original format. We prefer replacement figures containing vector/editable objects rather than embedded images. Preferred file formats are eps, ai, tiff and pdf.The file in original format has been attached.

Preconcentration and Determination Of Fluoxetine and Norfluoxetine in Biological and Water Samples with β-cyclodextrin Multi-walled Carbon Nanotubes as a Suitable Hollow Fiber Solid phase Microextraction Sorbent and High Performance Liquid Chromatography

‒A simple, selective and sensitive hollow fiber solid phase microextraction (SPME) combined with HPLC for the determination of fluoxetine (FLX) and norfluoxetine (NFLX) in human urine and real water samples has been developed and fully validated. Two solid phase microextraction sorbents, β-cyclodextrin functionalized multi-walled carbon nanotubes (βCD-MWCNTs) and acyl chloride functionalized MWCNTs, were synthesized and placed in the surface and pores of polypropylene hollow fiber by sol‒gel technique. In order to compare the analytical performance of βCD-MWCNTs as a new SPME sorbent with acyl chloride functionalized MWCNTs and MWCNTs, the hollow fiber device was directly immersed into the sample solution under a magnetic stirring. The βCD-MWCNTs are quite effective for extraction of fluoxetine and norfluoxetine. The extraction parameters such as pH of donor phase, donor phase volume, stirring rate, extraction time, type and volume of desorption solvent, and desorption time were thoroughly optimized. Under optimal conditions, the proposed method shows good linearity in the range of 1‒340 and 0.9‒360 ng/mL with a correlation coefficients of 0.9952 and 0.9967, low limits of detection of 0.4 and 0.3 ng/mL, and the high pre-concentration factors of 144 and 151 for determination of FLX and NFLX, respectively. Usage of proposed method for determination of FLX and NFLX in human urine and real water samples demonstrated a promising, simple, selective and sensitive sample preparation and determination method that can be applied in routine analysis.

Determination of quercetin using a molecularly imprinted polymer as solid-phase microextraction sorbent and high-performance liquid chromatography

A novel sorbent for solid-phase microextraction (SPME) based on molecularly imprinted polymers (MIPs) was developed to determine of quercetin by high-performance liquid chromatography -UV detection (HPLC-UV). Sol-gel process as a simple method was used to prepare the sorbent. The combination of MIP and SPME increased the selectivity and stability of the SPME fiber. First, stainless steel (SS) wires were modified and then MIPs synthesized through a sol-gel method using 3-aminopropyltriethoxysilane (APTES) as a functional monomer and tetraethyl orthosilicate (TEOS) as a cross link agent. The prepared MIP was characterized by field emission scanning electron microscopy (FESEM), Fourier-transform infrared spectroscopy (FTIR) and thermal gravimetric analysis (TGA). Influential parameters on extraction efficiency were investigated and optimized. The maximum extraction efficiency was obtained under the optimum conditions including: pH 4.5, extraction time 30 min, stirring rate 500 rpm, desorption time 20 min and MeOH/AcOH (9:1 V/V) as a desorption solvent. The proposed method was found to be linear for the concentration range from 0.05 to 100 μg mL−1 with R2 = 0.9998. The limit of detection (LOD) was 9.94 ng mL−1. Relative standard deviations (RSD) (n = 6) using a single fiber and between fibers were 2.3 and 5.0%, respectively. The proposed MIP-SPME fiber was successfully applied for selective determination of quercetin in tea and coffee samples.