Desorption Solvent Volume Research Articles

An in vitro assessment for human skin exposure to parabens using magnetic solid phase extraction coupled with HPLC

Skin contact was a significant source of human exposure to parabens during the use of personal care products. In this study, a novel and simple in vitro evaluation method for human skin exposure to parabens was established for the first time. Firstly, magnetic porous carbon (MPC) derived from discarded cigarette butts was prepared as an adsorbent of magnetic solid-phase extraction (MSPE), which provided a fast and efficient sample preparation method with satisfactory extraction performance for parabens in cosmetics and was easy to couple with high performance liquid chromatography. Secondly, the extraction conditions were optimized including the etching ratio of KOH, amount of MPC, extraction time, pH, salt concentration, desorption solvent volume and desorption time. Under the optimized conditions, the limits of detection were between 0.25 and 0.34 ng mL−1 and the spiked recoveries were in the range of 85.8–112.6%. Thirdly, the developed method was successfully employed to determine five typical parabens in real unspiked cosmetic samples, and two parabens were detected at a relatively high level. Then, the developed method was applied to in vitro assays. The absorbable dose of parabens in cream was investigated and in vitro experiments were further designed with agarose-simulated skin to demonstrate the penetration ability of parabens. In conclusion, these results indicated that parabens did have the risk of entering the body through the skin and the exposure was preferably no more than 3 h with skin contact.

Spin-column micro-solid phase extraction of phthalate esters using electrospun polyacrylonitrile/iron (III)/Mg-based metal-organic framework 88B followed by GC analysis

An electrospun composite polyacrylonitrile/iron (III)/Mg-based metal–organic framework 88B (PAN/Fe/Mg-MIL-88B) was prepared, and then utilized as a viable sorbent for the simultaneous determination of five phthalate esters in store-bought bottled mineral water and orange juice, urine, plasma, and two different types of cream and lipstick applying spin column micro solid-phase extraction (SC-μSPE) method. The synthesis of the electrospun nanofibers was surveyed using energy-dispersive X-ray spectroscopy, X-ray diffraction analysis and Fourier transform infrared spectroscopy, while the morphology of the composite was investigated using field emission scanning electron microscopy. The presence of Fe/Mg-MIL-88B with high quantity of functional groups and porous structure in the polymer matrix endows the PAN nanofibers with high extraction efficiency. The effect of MOF% in the composite nanofibers, amount of sorbent, sample pH, type and volume of desorption solvent, salt concentration, number of cycles, and centrifugation speed were optimized. Under the optimal conditions, the calibration plots for dimethyl phthalate (DMP), diethyl phthalate (DEP), and diallyl phthalate (DAP) were linear within the range of 1.0–1000.0 ng mL−1; and 0.5–1000.0 ng mL−1 for diisobutyl phthalate (DIBP) and dibutyl phthalate (DBP). The limits of detection were lower than 0.30 ng mL−1 for DMP, DEP, and DAP and 0.15 ng mL−1 for DIBP and DBP by GC-FID. The data related to the relative standard deviations were in the range of 4.1%–6.3% (intra-day, n = 5) and 6.4%–7.9% (inter-day, n = 3) in the span of three days. Finally, the applicability of the method was scrutinized for the quantification of analytes of interest in spiked samples, and satisfactory recoveries were attained within the range of 84.8–102.8%.

Cyclodextrin-starch hard gel as an efficient green sorbent for dispersive micro solid-phase extraction of eight polycyclic aromatic hydrocarbons from environmental water samples

Determination of organic pollutants in environmental water samples is known as the challenging field. In this study, we have reported an extraction methodology based on the β-cyclodextrin-starch composite (β-CD-starch) as a sorbent for the extraction of polycyclic aromatic hydrocarbons (PAHs) from water samples. The synthesis procedure of sorbent was straightforward and convenient. A hard gel of wheat starch in combination with different kinds of CDs/maltodextrin (MD) was prepared. It then was applied as a sorbent in dispersive micro solid-phase extraction (d-µ-SPE) of target analytes (i.e., naphthalene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, and benzo[a]pyrene) from aqueous solutions. Optimization of the extraction process was followed by the investigation of the effective parameters on the extraction efficiency; like sorbent type (based on the type of used CD/MD) and its mass amount, type and volume of desorption solvent, the salt concentration of sample solution, and the extraction/desorption times. Under the optimal extraction conditions, good linear ranges between 0.1 and 1000 ng/mL with r2 > 0.991 were obtained. The detection limit was from 0.01 to 0.07 ng/mL, and the limit of quantification was varied over the range 0.04–0.24 ng/mL. As well, the enrichment factor of the extraction method was calculated between 84.1 and 94.8 (with a maximum value of 100). The efficient and sensitive proposed method was then applied for extraction and determination of PAHs in agricultural and rainwater samples along with the GC-FID system, and acceptable results were received.

Solid-phase extraction of non-steroidal anti-inflammatory drugs in human plasma and water samples using sol–gel-based metal-organic framework coating

In this research, the Cu-based metal-organic framework (MOF-199) was fabricated and coated on the stainless steel mesh as substrates through sol−gel procedure. Then the coated substrates were placed in a small column known as solid-phase extraction cartridge. The SPE based coated stainless steel mesh coupled with high-performance liquid chromatography-UV detector (HPLC-UV) was used for the fast extraction, and quantification of non-steroidal anti-inflammatory drugs (NSAIDs) from human plasma and water samples. To find optimum extraction conditions, the impacts of effective parameters on analytical performance like sample pH, sample volume, type, and volume of desorption solvent were optimized. At the optimized conditions, calibration graphs of analytes were linear in the concentration range of 0.03−300 ng mL−1 for water samples, and 0.1−200 ng mL−1 for plasma samples. The correlation coefficients were in the range of 0.9938 to 0.9989. Also, the limits of detection (LODs) were from 0.01 to 0.02 ng mL−1 for water samples and 0.03 to 0.1 ng mL−1 for plasma samples. The cartridge repeatability was studied at different values, and the relative standard deviations (RSDs%) were achieved between 3.5 and 5.1%. Consequently, this procedure was successfully used in the extraction and detection of NSAIDs in real water and plasma samples with relative recoveries ranged from 93.6 to 99.6%.

Core-shell magnetic zeolite imidazolate framework-8 as adsorbent for magnetic solid phase extraction of brucine and strychnine from human urine

Core-shell magnetic zeolite imidazolate framework-8 (Fe3O4@PAA@ZIF-8) was successfully synthesized and first employed as adsorbent of magnetic solid-phase extraction (MSPE) for the determination of brucine and strychnine in human urine sample coupled with high performance liquid chromatography. The as-prepared Fe3O4@PAA@ZIF-8 was characterized by transmission electron microscopy, Fourier-transform infrared spectrometry, X-ray diffraction, vibrating sample magnetometer and zeta potential analysis. Main parameters affecting the MSPE efficiency, including amount of adsorbent, sample solution pH, extraction time, ionic strength, desorption solvent, desorption time and desorption volume were further optimized. Under the optimized conditions, the proposed method provided good linearity (5.0–1000.0 μg L−1) with determination coefficients between 1.0000 and 0.9998, low limits of detection in the range of 1.1–1.2 μg L−1, and excellent reproducibility with relative standard deviations of less than 7.7%. The intra-day and inter-day precision were 1.5–3.2% and 2.1–7.2%, respectively. Satisfactory spiked recoveries were between97.2% and 115.4% with the relative standard deviations less than 6.3%. The results demonstrated that Fe3O4@PAA@ZIF-8 composite was a promising magnetic adsorbent for the preconcentration of brucine and strychnine in human urine sample.

Magnetic Solid-Phase Extraction of Lawsone Using Polyphenol-Coated Magnetic Nanoparticles: Synthesis, Characterization and examination

A novel polyphenol-coated CoFe2O4 system with sorption capacity of lawsone was synthesized as a magnetic sorbent by chemical oxidative polymerization process for magnetic solid-phase extraction of lawsone. The synthesized nanosorbent showed a spherical morphology with diameters under 50 nm by scanning electron microscopy images. The extraction efficiency of this sorbent was studied toward the extraction of lawsone from saline aqueous solution in dispersion mode. Major parameters including the type and volume of desorption solvent, amount of sorbent, desorption time, extraction time, extraction temperature, ionic strength, and pH were optimized. Under the optimum conditions, the relative standard deviation in 0.005 µg mL−1 (inter-day n = 6; intra-day: n = 6; and sorbent to sorbent n = 4) were obtained as 5.2, 8.07, and 11.7%, respectively. A linear calibration curve in the range of 0.003–0.5 µg mL−1 with R2 = 0.993 was obtained. The limit of detection and limit of quantification of the method were 0.001 µg mL−1 and 0.003 µg mL−1, respectively. The relative recovery percentages were in range of 90–96.4% for henna leaves, henna shampoo, and henna dermal lotion real samples.

Preparation and application of Fe3O4@ SiO2@ poly (o-phenylenediamine) nanoparticles as a novel magnetic sorbent for the solid-phase extraction of tellurium in water samples and its determination by ET-AAS

A novel magnetic polymer (Fe3O4@ SiO2@ PoPD) is synthesized for the magnetic solid-phase extraction (MSPE) of tellurium from water samples and its determination by electrothermal atomic absorption spectroscopy (ET-AAS). The morphology, composition and magnetic properties of the synthesized nanoparticles are characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), energy-dispersive X-ray spectroscopy (EDX) and vibrating sample magnetometery (VSM). The factors affecting separation and preconcentration of tellurium including the amount of sorbent, composition of sorbent material, extraction time and temperature, desorption time and temperature, pH and ionic strength of the sample solution, desorption solvent type, concentration and volume are studied. Under optimized experimental condition, the linear range and the detection limit of the method are 0.08–1.9 ng mL−1 (R2 = 0.9879) and 0.05 ng mL−1, respectively. The percent recovery of tellurium from real samples spiked at 0.5 ng mL−1 is more than 98%. The intraday and interday relative standard deviations for a batch of the sorbent at above concentration level are 4.3 and 5.6%, respectively. The sorbent-to-sorbent RSD% is 8.9%. Finally, the developed method is successfully applied to the analysis of tellurium in some real samples.

In-situ synthesis of nanocubic cobalt oxide @ graphene oxide nanocomposite reinforced hollow fiber-solid phase microextraction for enrichment of non-steroidal anti-inflammatory drugs from human urine prior to their quantification via high-performance liquid chromatography-ultraviolet detection

The in-situ synthesis and application of nanocubic Co3O4-coated graphene oxide (Co3O4@ GO) was introduced for the first time to present a cost-effective, stable and convenient operation and a simple device for hollow fiber solid-phase microextraction (HF-SPME) of four selected nonsteroidal anti-inflammatory drugs (NSAIDs) including diclofenac, mefenamic acid, ibuprofen and indomethacin. The extracted analytes were desorbed by an appropriate organic solvent and analyzed via high-performance liquid chromatography-ultraviolet detection (HPLC-UV). The prepared sorbent was approved using different characterization methods such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The variables effective on the Co3O4@GO-HF-SPME method including extraction time, desorption time, desorption solvent volume, sample pH, stirring rate and ionic strength were screened via Plackett–Burman design and then optimized by Box–Behnken design. Under optimal condition, the calibration curves were linear within the range of 1.0–200.0 µg L−1 of analyte concentration with detection limits of 0.18–1.1 µg L−1 and the relative standard deviations less than 10.1%. The limits of quantification (LOQs) were in the range of 0.60–3.67 µg L−1. Matrix effect was not observed with this method; therefore, standard addition is not necessary for quantification of target compounds. The enrichment factors were obtained in the range of 49–68. The relative recoveries of the urine sample analysis were calculated in the range of 93–102%. Finally, the presented method exhibited good sensitivity, excellent repeatability, high reusability and acceptable precision, which will be a promising method to analyze various nonsteroidal anti-inflammatory drugs in urine samples.

Magnetic Fe3O4@SiO2@β-cyclodextrin for solid phase extraction of methyl parathion and fenthion in lettuce samples.

In this study, magnetic Fe3O4@SiO2@β-cyclodextrin copolymerized microparticles were synthesized and applied for the extraction of methyl parathion and fenthion in lettuce samples followed by HPLC-UV detection. The magnetic β-cyclodextrin copolymerized microparticles were prepared by dispersion polymerization with acryloyl β-cyclodextrin as the functional monomer and ethylene glycol dimethyacrylate as the crosslinker. The composite magnetic microparticles were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, magnetic measurement, and thermogravimetric analysis, and used as the adsorbent of magnetic solid-phase extraction (MSPE) for methyl parathion and fenthion. The extraction conditions including sample pH and ionic strength, desorption solvent type and volume, and adsorption and desorption times were optimized. Under the optimal extraction conditions, an MSPE-HPLC-UV method was developed for the detection of methyl parathion and fenthion in lettuce. Wide linear ranges of 1.0-200 μg kg-1 (R2 = 0.9998) for methyl parathion and 1.5-200 μg kg-1 (R2 = 0.9978) for fenthion were obtained and the limits of detection were 0.3 μg kg-1 for methyl parathion and 0.5 μg kg-1 for fenthion in lettuce, respectively. The proposed method was applied for the determination of methyl parathion and fenthion in lettuce with satisfactory recoveries between 89.2-101.2%, and relative standard deviations were less than 9.1%. Thus, the MSPE-HPLC-UV method has high accuracy and sensitivity for the analysis of methyl parathion and fenthion in lettuce samples.

Determination of sulfonamide residues in animal foodstuffs by magnetic dispersive solid-phase extraction using magnetic carbon nanocomposites coupled with ion pair-dispersive liquid\u2013liquid micro-extraction combined with HPLC-DAD

In this study, magnetic-dispersive solid-phase extraction coupled with ion pair-dispersive liquid–liquid micro-extraction (MSPE-i-DLLME) was used to the pre-concentration and extraction of five sulfonamides residues (sulfadiazine, sulfathiazole, sulfacetamide, sulfamethazine and sulfamethoxazole) in animal foodstuffs. The sulfonamides are extracted using magnetic carbon nanocomposite and then eluted with acetonitrile. In the DLLME step, the target analytes are collected in 1-octanol containing 10% Aliquat-336 (as extraction solvent). Finally, the compounds are quantified by HPLC with DAD detection. The extraction parameters optimized using the one at the time and central composite design methods. Under the optimized conditions: sample solution volume was 100 mL; initial pH: 12, amounts of MCNs: 30 mg; desorption solvent (ACN) volume, 1 mL; desorption condition, 10 min sonication at two step; extraction solvent (1-octanol + 10% aliquat) volume, 115 µL; pH of DLLME step, 3; salt effect, 24.6%, (w/v) NaCl; centrifuge, 5 min, 4000 rpm. In these extraction conditions, the proposed procedure represented good pre-concentration factors between 130 and 490; detection limits in the range from 0.01 to 5 μg kg−1 (at S/N = 3), and linear response in the 0.1–400 μg kg−1 concentration range. The method is successfully applied to the determination of sulfonamides residues in animal foodstuffs.

Preparation of coal-derived magnetic carbon material for magnetic solid-phase extraction of fungicides from water samples

A magnetic solid-phase extraction method has been developed for the extraction and analysis of some fungicides in environmental water samples. Azoxystrobin, chlorothalonil, cyprodinil and trifloxystrobin were the target fungicides selected. First, a carbon material was obtained from the raw coal sample collected from Zonguldak region by ash removal process and then a magnetic C/Fe3O4 composite was produced from the carbon material using a single-step thermal method. The magnetic C/Fe3O4 composite was characterized by N2 adsorption-desorption, X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy. This composite was then used as an adsorbent for the magnetic solid-phase extraction of fungicides from water samples followed by high-performance liquid chromatographic analysis. Experimental parameters affecting the extraction efficiency such as adsorbent amount, type and volume of desorption solvent, adsorption and desorption time, ionic strength, and pH were optimized. Under the optimized conditions, the extraction efficiency for azoxystrobin, chlorothalonil, cyprodinil and trifloxystrobin was found to be 71%, 44%, 41% and 70%, respectively. The method detection limits for fungicides were found to be in the range of 0.4-1.1 µg L-1. The relative standard deviations were found to be lower than 6.6% and 6.9% for intra-day and inter-day precisions, respectively. The extraction of related fungicides from water samples collected from Zonguldak region was carried out efficiently. The recoveries obtained from spiked water samples were in the range of 71–106%.

Enhanced microextraction of endocrine disrupting chemicals adsorbed on airborne fine particulate matter with gas chromatography–tandem mass spectrometric analysis

A novel double-microextraction approach, combining dispersive liquid-liquid microextraction (DLLME) and vortex-assisted micro-solid-phase extraction (VA-µ-SPE) was developed. The procedure was applied to extract endocrine disrupting chemicals (EDCs) consisting of three phthalate esters (PEs) and bisphenol A (BPA) associated with PM2.5 (airborne particulate matter with aerodynamic diameter ≤ 2.5 µm). Gas chromatography–tandem mass spectrometry (GC–MS/MS) was used for determination of the analytes. These analytes were first ultrasonically desorbed from PM2.5 in a 10% acetone aqueous solution. DLLME was used to first preconcentrate the analytes; the sample solution, still in the same vial, was then subjected to VA-µ-SPE. The synergistic effects provided by the combination of the microextraction techniques provided advantages such as high enrichment factors and good cleanup performance. Various extraction parameters such as type and volume of extractant solvent (for DLLME), and type of sorbent, extraction time, desorption solvent, volume of desorption solvent and desorption time (for µ-SPE) were evaluated. Multi-walled carbon nanotubes were found to be the most suitable sorbent. This procedure achieved good precision with intra- and inter-day relative standard deviations of between 1.93 and 9.95%. Good linearity ranges (0.3-100 ng/mL and 0.5-100 ng/mL, depending on analytes), and limits of detection (LODs) of between 0.07 and 0.15 ng/mL were obtained. The method was used to determine the levels of PEs and BPA in ambient air, with concentrations ranging between below the limits of quantification and 0.48 ng/m3. DLLME–VA-µ-SPE-GC–MS/MS was demonstrated to be suitable for the determination of these EDCs present in PM2.5.

Dispersive micro solid-phase extraction with gas chromatography for determination of Diazinon and Ethion residues in biological, vegetables and cereal grain samples, employing D-optimal mixture design

In the present study, a dispersive solid-phase microextraction/gas chromatography-flame ionization detection was developed for extraction and simultaneous measurement of two organophosphorus pesticides (Diazinon and Ethion) residues in rice, cucumber, tomato, and mice liver samples. For this purpose, magnetic NH2-MIL-53(Al)@ Chitosan was synthesized and with coating magnetic Fe3O4 nanoparticles and with NH2-MIL-53(Al) in the presence of Chitosan to prepare an effective and magnetic sorbent for the extraction of Diazinon and Ethion. The value of sorbent components was optimized with a D-optimal mixture design. The optimum percentages of the sorbent components, including magnetic Fe3O4 nanoparticle, NH2-MIL-53(Al), and Chitosan, were 21, 45, and 33%, respectively. Magnetic NH2-MIL-53(Al)@ Chitosan nanocomposites were characterized by FTIR, SEM, and VSM techniques. The effects of various parameters on the extraction efficiency of Diazinon and Ethion, including pH, type and volume of desorption solvent, dispersion time, sorbent amount, extraction time, sample solution volume, and desorption time, were studied and optimized by using the design of the experiment. The calibration curves were linear in the range of 0.23–220 and 0.13–200 µg L−1 for the determination of Diazinon and Ethion, respectively. Besides, LODs of 0.07 and 0.04 µg L−1 were obtained for the measurement of Diazinon and Ethion, respectively. Intra-day and inter-day RSDs were lower than 4.12 and 5.59% for the determinations of the analytes (n = 5) with a concentration of 10.0 µg L−1 under the optimum conditions, respectively. The proposed procedure was effectively applied to determine the Diazinon and Ethion residues in the rice, cucumber, tomato, and mice liver samples with a proper recovery in the range of 91.25–104.35 % and a low RSD (≤6.45%).

Determination of four antiepileptic drugs with solvent assisted dispersive solid phase microextraction – Gas chromatography–mass spectrometry in human urine samples

In this paper solvent assisted dispersive solid-phase microextraction (SA-DSPME) as a rapid and comprehensive sample preparation method was developed to extract and cleanup four antiepileptic drugs (AEDs); valproic acid, phenobarbital, levetiracetam, and pregabalin from human urine samples. In the procedure, the dispersion of the sorbent was attained by rapid injection of a mixture of the adsorbent and disperser solvent into the aqueous sample to increase the contact surface and reduce the extraction time and amount of sorbent consumption. Several sorbents such as magnetic Fe3O4, Fe3O4@graphene, Fe3O4@graphene oxide, Fe3O4@MWCNTs, Fe3O4@SiO2, Fe3O4@SiO2@TiO2, Fe3O4@Chitosan, and NiO NPs were tested to extract the target drugs and the results compared. Among them, Fe3O4@SiO2 was chosen as the best sorbent, and its structure characterized using FESEM, FTIR, and EDX. Besides, effective factors in the SA-DSPME, including the type of disperser solvent and desorption solvent, extraction time, desorption time, pH, and disperser solvent and desorption solvent volume, were optimized using one factor at a time and design experiment strategy. Under the optimum conditions, the calibration curves were linear in the range of 0.2–100 ng mL−1 for valproic acid and phenobarbital, and 0.4–120 ng mL−1 for levetiracetam and pregabalin. Limit of detections and limit of quantifications were lower than 0.11 and 0.4 ng mL−1 for the analytes. Besides, the procedure showed suitable relative standard deviations (≤3.8%) and preconcentration factors (≥133.9) for the determination of the antiepilepsy drugs. Analysis of human urine samples confirmed that the SA-DSPME-GC procedure is an appropriate method for measuring the target drugs in biological samples with recoveries between 92.9 and 103.2 % and RSD less than 4.7%.

Trace Extraction of Metoprolol from Plasma, Urine and EBC Samples Using Modified Magnetic Nanoparticles Followed by Spectrofluorimetric Determination for Drug Monitoring Purposes

Background: Metoprolol is a selective β1-adrenergic receptor antagonist (β-blockers). It is widely used for the treatment of hypertension and other related diseases. Metoprolol can be used as a doping agent in sports, thus has been included in the list of forbidden drugs. In Iran, therapeutic drug monitoring (TDM) of β-blockers is an applied procedure in some cases. A therapeutic regimen could be easily managed by the determination of drug levels in biological fluids which is a relatively costly process and requires highly skilled technical staff. Using a simple and low-cost analytical procedure may help to use TDM in routine clinical practice. Methods: A real biological sample was prepared and its pH was adjusted to 3-4, then metoprolol was quickly extracted using magnetic iron oxide nanoparticles (MIONPs) modified by sodium dodecyl sulfate (SDS) and determined by applying spectrofluorimetry at 340 ± 3 nm after excitation at 283 ± 3 nm. Results: The extraction and determination conditions including, the amount of MIONPs and SDS, pH of the solution, standing time, desorption solvent type and volume were investigated and adjusted. Calibration curves were linear over the concentration range of 6–100 ng/mL for plasma and 5–100 ng/mL for water, urine and exhaled breath condensate samples, respectively. Intra and inter-day precision values for determination of metoprolol in different samples were less than 5.6 % and 6 %, respectively, and accuracy (as a relative error) was better than 5 %. Moreover, standard addition recovery tests were carried out, and the analytical recoveries ranged from 86 % to 113 %. The limits of detection (LOD) and limits of quantification (LOQ) of metoprolol were found to be in the range of 2.1-3.4 ng/mL and 6.3- 10.2 ng/mL, respectively. Conclusion: The developed method was successfully applied to biological samples taken from a volunteer who was given an oral tablet of 50 mg metoprolol.

Development of a new solid phase extraction method for sensitive determination of some carbamate pesticides in water using poly(EGDMA-MATrp) microbeads

In this work, poly(ethylene glycol dimethacrylate-N-methacryloyl-L-tryptophan methyl ester) [poly(EGDMA-MATrp)] microbeads (average diameter = 106–300 µm), were synthesized by suspension polymerization technique. The microbeads showed strong affinity and allowed for solid phase extraction (SPE) of two common pesticides; pirimicarb and propoxur in environmental water samples. Some SPE process parameters such as the desorption solvent type, solvent volume, pH and salt concentration were optimized. When it was coupled with high pressure liquid chromatography (HPLC-PDA) for the determination of analytes, the linear ranges were about 10–800 ng mL−1 and the detection limits were 0.95–2.85 ng mL−1. Also the correlation coefficients (0.9949–0.9991) and precisions (2.15–2.52% RSD, n = 3) were determined. The technique was also applied to the enrichment of these pesticides in various environmental water samples. However, no target analyte was detected in the samples. Therefore, samples were spiked and recovery values were obtained in the range of 95.8–104.2% with RSDs of 2.6–6.6%.

Evolution of cross-linked polyethyleneimine/SABO®STAB as an efficient sorbent for extraction of pesticides in fruit and vegetable juices

The novel cross-linked polyethyleneimine/SABO®STAB was synthesized and used as an efficient sorbent for dispersive micro-solid phase extraction of pesticides before gas chromatography–micro-electron capture detection. The sorbent was fully characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, differential scanning calorimetry, Brunauer–Emmett–Teller, and Barrett–Joyner–Halenda techniques which confirmed thermally stable cross-linked polymer composite with large surface area and mesoporous morphology. The significant parameters, including type and volume of desorption solvent, extraction time, sorbent dosage, and pH of the sample solution, were optimized. The analytical characteristics of the method were validated using a matrix-matched calibration method. The linear dynamic range was 0.85–250 µg L−1 with good determination coefficients (R2 > 0.996). The limits of detection were 0.25–0.44 µg L−1. Finally, the method was applied for the determination of chlorpyrifos and hexaconazole in celery and apple juices, and the relative recoveries were in the range of 75–116% with the RSDs of 2.7–3.6%.

Magnetic dispersive solid-phase microextraction for determination of two organophosphorus pesticides in cucumber and orange samples

In this study, a magnetic dispersive solid-phase microextraction technique based on chitosan–iron oxide magnetic nanocomposite (CS@Fe3O4) as sensitive and inexpensive sorbent was developed for the preconcentration and simultaneous determination of malathion and fenitrothion in fruit and vegetable samples before determining with GC–FID. The structures, morphologies, and properties of the nanocomposite were characterized by Fourier transform infrared, transmission electron microscopy, and scanning electron microscopy. The significant factors such as pH, sample solution volumes, extraction time, the type and amount of nanocomposites, type and volume of desorption solvent, and desorption time were investigated and optimized. One factor at the time and an experimental design approach were utilized to optimize the selected factors. In the optimal conditions, the linear range for malathion and fenitrothion was 1.0–400.0 and 3.4–600.0 µg L−1 with a suitable R2 (≥ 0.992), respectively. The intra-day and inter-day relative standard divisions (RSDs) were lower than 4.83 and 4.90 for both analytes, respectively. Limit of detection for the determination of malathion and fenitrothion was 0.3 and 1.0 ng mL−1, respectively. The proposed method showed a high recovery percentage in the range of 95.8–106.0 and low RSDs (≤ 5.0) for the determination of malathion and fenitrothion in the cucumber and orange samples.

Spherical conjugated microporous polymers for solid phase microextraction of carbamate pesticides from water samples.

Conjugated microporous polymers (CMPs) with uniform morphology have shown fascinating application in the separation science. In this study, metal-free Knoevenagel condensation was adopted to prepare spherical sp2 carbon-conjugated microporous polymers, which used tetrakis(4-formylphenyl)methane and 1,4-phenylenediacetonitrile as monomers. Due to the remarkable extraction capability for carbamate pesticides (CPs), the as-synthesized CMPs were fabricated as the coating for solid-phase microextraction (SPME). After optimized SPME parameters (adsorption time, salt concentration, sample pH, adsorption temperature, desorption time, desorption solvent and desorption volume), ten CPs in water samples were quantified by ultrahigh performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS). Linearity in the range 0.005-100ng mL-1 with low detection limits of 0.00060-0.017ng mL-1 was obtained. The intra-day and inter-day precisions expressed as relative standard deviations were 1.5-8.1% and 1.1-8.0%, respectively. Fiber-to-fiber reproducibility was below 7.3%. The CMPs-SPME-UPLC-MS/MS method was applied to detect trace CPs in real water samples with relative recoveries from 91.8% to 108%.

Metal-organic frameworks derived magnetic porous carbon for magnetic solid phase extraction of benzoylurea insecticides from tea sample by Box-Behnken statistical design

Ferric oxide/carbon (Fe2O3@C) was fabricated via direct carbonization of metal-organic framework of iron (MOF-235) under argon atmosphere. The magnetic Fe2O3 nanoparticles are evenly embedded in porous carbon matrix, while original morphology of MOF-235 was well-maintained. The synthesized Fe2O3@C was used as magnetic sorbent for extracting five benzoylurea insecticides (BUs). The materials exhibited excellent extraction performance, which benefited not only from the strong π-π interaction and hydrophobic interaction (π-conjugated system), but also to the abundant adsorption sites and flexible transport channel (the interconnected 3D porous structure). A three-factor-three-level Box-Behnken design (BBD) was selected to optimize three greatly influential parameters: amount of adsorbent (A), desorption time (B) and volume of desorption solvent (C) by response surface methodology. The established method coupled to HPLC-UV detection showed wide linearity with the range of 0.2-450 μg•L-1, relatively low limits of detection (0.05-0.10 μg•L-1) with the relative standard deviation (RSD) (n=7) lower t than 5.47%. Moreover, the proposed method was successfully applied to analyze BUs in tea samples and investigate the removal effect of different washing on BUs residues from tea leaf. These results indicated that the synthesized Fe2O3@C is a promising adsorbent material for magnetic solid phase extraction of BUs at trace concentrations from tea samples.