High Enrichment Factors Research Articles

Lipid and protein corona of food-grade TiO2 nanoparticles in simulated gastrointestinal digestion

In the presence of biological matrices, engineered nanomaterials, such as TiO2, develop a biomolecular corona composed of lipids, proteins, etc. In this study, we analyzed the biocorona formed on the food grade TiO2 (E171) going through an in vitro simulated gastrointestinal digestion system in either a fasting food model (FFM), a standardized food model (SFM), or a high fat food model (HFFM). Lipids and proteins were extracted from the biocorona and underwent untargeted lipidomic and label-free shotgun proteomic analyses. Our results showed that the biocorona composition was different before and after food digestion. After digestion, more diverse lipids were adsorbed compared to proteins, most of which were the enzymes added to the simulated digestion system. The corona lipid profile was distinct from the digested food model they presented in, although similarity in the lipid profiles between the corona and the food matrix increased with the fat content in the food model. The corona formed in the two low-fat environments of FFM and SFM shared a higher degree of similarity while very different from their corresponding matrix, with some lipid species adsorbed with high enrichment factors, indicating specific interaction with the TiO2 surface outperforming lipid matrix concentration in determination of corona formation. Formation of the biocorona may have contributed to the reduced oxidative stress as well as toxicological impacts observed in cellular studies. The present work is the first to confirm persistent adsorption of biomolecules could occur on ingested nanomaterials in food digestae. More future studies are needed to study the in vivo impacts of the biocorona, and shed light on how the biocorona affects the biotransformations and fate of the ingested nanomaterials, which may impose impacts on human health.

Magnetic Fraction of Fly Ash as a Low-Cost Magnetic Adsorbent for Selective Capture of Phosphoproteins

In the present study, the magnetic fraction of fly ash was separated from the bulk material using a conventional magnet, yielding approximately 50% w/w. As the magnetic fraction of fly ash contains a high content of aluminum oxide, which is recognized as a phosphate adsorbent, and ferromagnetic iron oxides, it is potentially useful as a magnetic solid-phase extraction adsorbent of phosphoproteins. The results showed that the magnetic fraction of fly ash displayed a high enrichment factor of approximately 130-fold as a magnetic solid-phase extraction adsorbent. The phosphoprotein bound-magnetic fraction was efficiently isolated from the sample solution using a conventional magnet. The adsorbent was further applied to the isolation of phosphoproteins from biological samples, i.e., ovalbumin from egg white and caseins from milk. The sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the enrichment of phosphoproteins revealed that the eluted fraction contained more purified phosphoproteins comparing to the initial diluted samples. In addition, the adsorbent may be reused with acceptable adsorption capacity at least three times. The magnetic solid-phase extraction using the magnetic fraction of fly ash as an adsorbent is effective, simple and reusable. Therefore, the magnetic fraction of fly ash may be an alternative low-cost magnetic adsorbent for the sequestration of phosphoproteins from complex samples.

Seasonal variations, source apportionment, and health risk assessment of trace metals in PM2.5 in the typical industrial city of changzhi, China

Studying the source-specific health risks of trace metals in PM2.5 is important for controlling its emission sources that are hazardous to human health. In this study, PM2.5-bound trace metals were analyzed during winter, spring, summer, and autumn in 2018 in Changzhi, a typical industrial city in China. The results revealed that the annual concentration of total trace metals in PM2.5 was 7531.9 ng m−3 in the study area, and the concentration was maximum in spring (14,781.7 ng m−3), followed by autumn (7163.8 ng m−3), winter (5237.0 ng m−3), and summer (3226.1 ng m−3). Dry and continual windy days in spring often led to high concentrations of trace metals in Changzhi. Trace metals with high enrichment factor (>100), such as Cd, Sn, Pb, and Zn, were predominantly released from coal combustion. Four sources, such as coal combustion, traffic emissions, resuspended dust, and industry, were established by positive matrix factorization, with contributions to PM2.5-bound trace metals of 29.5%, 26.6%, 26.3%, and 17.6%, respectively. In terms of their contribution to cancer risk, the top contributor both for children and adults was industry, with 1.50×10−6 and 5.99×10−6, respectively, both of which were higher than the safe level (1 × 10−6); coal combustion ranked second (0.49 × 10−6 and 1.94 × 10−6 for children and adults, respectively). In addition to the advancement of control measures for pollutants and control of industrial production, more attention should also be given in limiting coal consumption through the use of clean energy (e.g., natural gas).

Comparison of sandstone and mudstone with different methods for assessing toxic element contamination in the Early–Middle Jurassic sediments of Gümüşhane (NE Turkey)

To investigate the vertical changes of toxic elements in Jurassic sediments, sampling was performed in four sites. Samples were collected from sandstones and mudstones/marls and analyzed for some toxic elements (Cu, Pb, Zn, As, Ni and V). Results exhibited that the sediment grain size played a significant role in controlling the concentrations of the toxic elements in the sediments. The mean toxic element contents of mudstones/marls were higher than those of sandstones (except Cu). The contamination level of toxic elements was detected by enrichment factor (EF), geo-accumulation index (Igeo), potential ecological risk index (Eir), pollution index (Pi) and united pollution index (PIn). The low EF, Igeo, Eir, Pi and PIn for Cu, Pb, Zn, Ni, V in the sandstones and Cu, Zn, Ni in the mudstones/marls exhibited an absence of clear these elements pollution. The high EF, Eir, Pi and PIn for As (9.7, 73, 7 and 29, respectively, as mean values) in the sandstones and for As (49.3, 222, 22 and 75, respectively, as mean values) Pb (8.8, 24, 5 and 19, respectively, as mean values), V (8.3, 15, 7 and 39, respectively, as mean values) in the mudstones/marls indicated significant contamination. Additionally, according to the potential ecological risk (RI) values, the sandstones had low potential ecological risk for the toxic elements (RI < 150) and the mudstones/marls had moderate potential ecological risk (150 ≤ RI ≤ 300). The potential ecological risk As, Pb, V (especially As) were higher in urban areas than in agricultural activities. Therefore, the source of As, Pb, V could be gasoline combustion, burning coal and vehicle exhausts. The contents of these elements generally increased from bottom to top of the measured stratigraphic sections, which indicated transported by atmospheric conditions.

Self-assembled supramolecular dispersive liquid-phase microextraction for concentration and determination of anthraquinone compounds in Rhubarb.

Self-assembled supramolecular dispersive liquid-phase microextraction combined with high-performance liquid chromatography was developed and introduced for simultaneous extraction and determination of the trace level rhein, chrysophanol, and physcion in Rhubarb. Compared with conventional dispersive liquid-phase microextraction, the proposed method used a self-assembled ternary supramolecular consisting of the mixed extraction solvent (heptanol and nonanol) and dispersant (acetone) to achieve high enrichment factors of target analytes. Several factors affecting performance were investigated and optimized, including the mixed extraction solvent, type and volume of the dispersant, the pH of sample phase, salt concentration, shaking time, volume of sample phase, centrifugation time, and rate. Meanwhile, the method mechanism of self-assembled supramolecular dispersive liquid-phase microextraction was analyzed and described. Under the optimized extraction conditions, the enrichment factors of rhein, chrysophanol, and physcion were 116.5, 325.9, and 356.1, respectively. Good linearities (r ≥ 0.9952) for all analytes, low limits of detection (less than 0.04ng/mL), satisfactory precisions (0.1-8.9%), and accuracies (recoveries, 88.2-104.1%) were achieved. The experimental results showed that the approach was simple, fast, with short extraction time, high enrichment factors, good linearities, and low limits of detection.

Effective enrichment and detection of trace polybrominated diphenyl ethers in water samples based on magnetic covalent organic framework nanospheres coupled with chromatography-mass spectrometry

Novel core shell structured magnetic covalent organic frameworks were synthesized at room temperature and first applied in water samples for the enrichment of trace polybrominated diphenyl ethers (PBDEs) through magnetic solid-phase extraction. The prepared materials were characterized through transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, vibrating sample magnetometer and X-ray photoelectron spectroscopy. During adsorption, the parameters affecting extraction and desorption efficiency were further optimized. Combined gas chromatography and mass spectrometry (GC/MS) revealed that high enrichment factors (275–292), low limits of detection (0.12–0.38 ng·L−1), wide linear ranges (0.5–1000 ng·L−1), and good reproducibility (intra-day 1.40%–4.31% and inter-day 5.14%–9.12%) were obtained under optimal conditions. The method successfully detected PBDEs in different water samples.

Facile synthesis of tubular magnetic fluorinated covalent organic frameworks for efficient enrichment of ultratrace polybrominated diphenyl ethers from environmental samples

Polybrominated diphenyl ethers (PBDEs), known as the most widely used brominated flame retardant, have received great public concern due to its hidden environment and health problems. Development of highly selective and sensitive analytical approaches for enrichment and detection of ultratrace PBDEs are in high demand. Conventional sample pretreatment techniques usually require tedious procedures, long time, and excessive consumption of solvent and sample, thus hindering ultrasensitive detection of PBDEs. To address this issue, we first reported a simple room-temperature approach for synthesis of tubular magnetic fluorinated covalent organic frameworks (MCNT@TAPB-TFTA). The introduction of fluorine atoms played multiple roles in improving the frameworks' hydrophobicity and the adsorption capabilities for PBDEs. Combined with atmospheric pressure gas chromatography-tandem mass spectrometry (APGC-MS/MS), several crucial parameters of magnetic solid-phase extraction (MSPE) including adsorbent dosage, adsorption time, pH, ion strength, the eluent, elution time and elution frequencies were examined in detail. The optimal method exhibited wide linear ranges (0.01–500 ng/L), low limit of detections (LODs, 0.0045–0.018 ng/L), good correlation coefficients (r ≥ 0.9977), and high enrichment factors (EFs, 1425–1886 folds) for eight PBDEs. Furthermore, this proposed method could be successfully applied to sensitive determination of ultratrace PBDEs in environmental samples, demonstrating the promising potential of the MCNT@TPAB-TFTA as an adsorbent in sample pretreatment.

Evaluating contamination impact of wastewater irrigation to soils in Zahedan, Iran.

With respect to water crisis, using urban wastewater to irrigate urban green spaces is an upcoming strategy. The pollution of lands irrigated with wastewater is one of the upcoming challenges. The main purpose of the present study was to investigate contamination indices of soils irrigated with wastewater. In this study, field experimental method in statistical form of totally random blocks with three reiterations for considered treatments was employed. To this end, one piece of three-hectare grass irrigated with wastewater and one piece of land irrigated with well water (control sample) were selected out of the green spaces of Zahedan refinery. Then, 30 compound samples were randomly taken from the depth of 0-50cm of three lands' soil. The refinery wastewater outlet and wall water were also sampled. Physicochemical and biological features of wastewater, wall water and soil samples irrigated with the refinery wastewater and well water were measured according to the standard methods. The obtained data were analyzed using MSTAT-C software. Based on the obtained results, the modified degree of contamination (mCd) of highly and lowly used elements in the considered soils in the experiment was less than 1, indicating a low-contamination status. PLI index of the mentioned elements in the surface soil of grass irrigated with wastewater was higher than 1 and by wall water was less than 1. The concentration of sulfur in surface soil of the two treatments under investigation was in a highly severe enrichment factor (EF ≥ 50). In addition, the concentration of nitrogen, magnesium, zinc and manganese in the surface soil of palm trees and that of manganese, copper and manganese in the surface soil of the grass irrigated with wastewater had a high enrichment factor (5 ≤ EF < 25). Geoaccumulation index (Igeo) of sulfur in the surface soil of the pieces irrigated with wall water (control) and that of potassium in the surface soil of the grass irrigated with wastewater were in no-contamination or average-contamination statuses (0 < Igeo ≤ 1). Other elements were in non-contaminated status (Igeo ≤ 0) in terms of Igeo. The results of investigation of soil contamination indices showed that the soil contamination status of the study area due to wastewater irrigation was low to medium. Therefore, periodic and more accurate monitoring of wastewater treatment plant of Zahedan can be used from this wastewater for landscapes irrigation.

Extraction of some antibiotics from propolis samples using homogenous liquid–liquid extraction coupled with deep eutectic solvent–based hollow fibre protected preconcentration

ABSTRACT Combination of counter current salting-out homogenous liquid–liquid extraction and deep eutectic solvent–based hollow fibre protected preconcentration method has been developed for the extraction of some antibiotics from propolis samples prior to their determination by ion mobility spectrometry. In this method, an appropriate amount of the powdered propolis is mixed with iso-propanol and deionised water to obtain a homogenous solution. Then, this solution is passed through a glass tube filled with sodium chloride. By this action, the fine droplets of iso-propanol are released and the analytes are extracted into them. The separated iso-propanol is taken and slowly entered into a hollow fibre. By doing so, the analytes are trapped in the pores of hollow fibre and the organic solvent is evaporated after a few minutes. After that, a few microlitres of a water-miscible deep eutectic solvent (prepared from N,N–dimethyl ammonium chloride and propionic acid) is added to elute the analytes from the pores of hollow fibre. Method validation studies indicated that the introduced method has low limits of detection (0.27–0.41 ng g–1) and quantification (0.91–1.37 ng g–1), high enrichment factors (562 –603) and extraction recoveries (84–90%), acceptable repeatability (relative standard deviation ≤ 9.2%) under the optimum conditions. Abbreviations: CCSHLLE: Counter current salting-–out homogenous liquid–liquid extraction; DES: Deep eutectic solvent; EF: Enrichment factor; ER: Extraction recovery; HBA: Hydrogen bond acceptor; HBD: Hydrogen bond donor; HF–LPME: Hollow fiber–liquid-phase microextraction; HPLC: High-performance liquid chromatography; IMS: Ion mobility spectrometry; LOD: Limit of detection; LOQ: Limit of quantification; LR: Linear range; RSD: Relative standard deviation.

Graphene intercalated with carbon nanosphere: a novel solid-phase extraction sorbent for five carbamate pesticides.

Graphene-carbon nanosphere composite (G@CNS) was prepared via a simple hydrothermal method. The G@CNS nanocomposite was characterized by X-ray diffraction, scanning electron microscope, surface area, and porosity analysis. The G@CNS was applied as a new sorbent for solid-phase extraction of five carbamate pesticides (tsumacide, carbaryl, isoprocarb, bassa, diethofencarb) prior toquantitative determination by high-performance liquid chromatography with ultraviolet detection at 208nm. Some experimental parameters including desorption conditions, sample pH, sample volume, and loading rate were studied carefully. Under the optimized condition, the method provided good linearity ranging from 0.3 to 100.0ngmL-1 with low limits of detection of 0.10-0.20ngmL-1 for grape juice, 0.10-0.30ngmL-1 for blend fruit juice, and 0.10-0.20ngmL-1 for water sample. Good method recoveries (80.2-110%) with relative standard deviations less than 7.2% and high enrichment factors (167-293) were achieved. Results demonstrated that this novel G@CNS can serve as a promising alternative sorbent for more applications. In this work, a graphene-carbon nanosphere (G@CNS) composite was synthesized via a simple hydrothermal method. Then, the G@CNS was served as a novel sorbent for solid-phase extraction of five carbamate pesticides (tsumacide, carbaryl, isoprocarb, bassa, diethofencarb) in juice and environmental water samples, followed by their quantitative analysis with high-performance liquid chromatography-ultraviolet detection.

Magnetic dispersive micro-solid phase extraction merged with micro-sampling flame atomic absorption spectrometry using (Zn-Al LDH)-(PTh/DBSNa)-Fe3O4 nanosorbent for effective trace determination of nickel(II) and cadmium(II) in food samples

In this work, Zn-Al layered double hydroxide (Zn-Al LDH) combined with polythiophene (PTH)/sodium dodecyl benzene sulfonate (DBSNa) and Fe3O4 was synthesized and used in a centrifugeless ultrasound-assisted dispersive micro solid phase extraction (UA-D-μSPE) technique for pre-concentration and separation of Ni2+ and Cd2+ ions. The final analysis of the analytes was carried out by the micro sampling flame atomic absorption spectrometry (MS-FAAS). The influences of several effective analytical parameters, including pH value, amount of nanosorbent, sonication time, and eluent volume, on the extraction efficiency were studied by experimental design method. In the optimal conditions, the linearity ranges of 5–300 and 2.5–100 ng mL−1 for the Ni2+and Cd2+ ions were attained, respectively. The limits of detection (LODs) of the method were 1.3 and 0.7 ng mL−1 for the Ni2+ and Cd2+ ions, respectively. The proposed method demonstrated to be suitable for concurrent extraction of studied metals in various vegetable and meat samples with high accuracy and enrichment factors.

Marine Bacteria Affect Saccharide Enrichment in Sea Spray Aerosol during a Phytoplankton Bloom

Saccharides are a large class of organic matter in sea spray aerosol (SSA) that can impact its climate-relevant properties. In seawater, saccharides are produced, exuded, and consumed by phytoplankton and heterotrophic bacteria (HB). Herein, we add the HB strains Alteromonas sp. (AltSIO), Pseudoalteromonas (ATW7), and Flavobacteria bacterium (BBFL7) to marine microcosms during phytoplankton blooms and directly probe the impact of HB on the composition and size of saccharides in seawater and SSA for the first time. Enrichment factors (EFs) for saccharide SSA relative to seawater were composition- and size-dependent, ranging from 100 to 930 000 in sub-micrometer SSA and from 38 to 3700 in super-micrometer SSA. For saccharides in two similar phytoplankton blooms, lower seawater concentrations coincided with higher EFs, which may explain high saccharide enrichments in remote marine locations. Increased enzyme activity within a day of HB addition corresponded to increases in saccharide EFs in sub-micrometer SSA, by a factor of 30 for the energy-storage saccharide glucose and by a factor of 2 for the structural saccharide xylose. Meanwhile, arabinose, released in response to microorganism stress, increased by a factor of 20 in super-micrometer SSA after a lag of 2 days. Observations of HB in SSA indicate that modifications to the saccharide pool in terms of composition and size occur in both seawater and SSA, which subsequently impact their enrichment in SSA. A better understanding the chemical, biological, and physical factors that contribute to the large enrichment of saccharides in SSA will advance our ability to predict SSA composition and its impact on Earth’s climate.

Combination of dispersive solid phase extraction with lighter than water dispersive liquid–liquid microextraction for the extraction of organophosphorous pesticides from milk

ABSTRACT In present work, an efficient, reliable and accurate analytical method has been used for the extraction of five organophosphorus pesticides (diazinon, chloropyrifos, phosalone, parathion-methyl and azinphos-methyl) from milk samples. The extracted analytes were determined with high performance liquid chromatography-diode array detector. For this purpose, the milk proteins are precipitated by trichloroacetic acid and the analytes dissolved in the supernatant phase are adsorbed onto an octadecyl silane sorbent. Then, acetone is contacted with the sorbent to elute the analytes and then it is mixed with toluene. The mixture is rapidly dispersed into deionised water filled into a syringe. To break down the obtained cloudy solution, 250 µL acetonitrile is added to the solution as a demulsifier. Finally, the collected organic phase in the tip of the syringe is collected, evaporated and reconstituted in mobile phase for using in determination of the analytes. Figure of merits were calculated for method validation and acceptable limits of detection (0.17–0.36 ng mL–1) and quantification (0.57–1.34 ng mL–1), high enrichment factors (395–460) and extraction recoveries (79–92%) were obtained. Inter- (n = 6) and intra-day precisions at a concentration of 3 ng mL–1 (each analyte) with relative standard deviations ≤7.2%, was obtained. Lastly the method was successfully used for determination of the analytes in some milk samples and chloropyrifos was found in one sample.

Modulated construction of imine-based covalent organic frameworks for efficient adsorption of polycyclic aromatic hydrocarbons from honey samples

Herein, we introduce a modulation strategy for the synthesis of imine based covalent organic frameworks (COFs) via the condensation of benzene-1,3,5-tricarbaldehyde with 1,3,5-tris (4-aminophenyl) benzene, whereby aniline was adopted as the monofunctional competitor. The introduction of aniline resulted in an enhanced crystallinity, surface area and pore volume, which is beneficial for the enrichment capability of the resulting COFs for the analytes. The optimized COF with the best extraction ability was selected as the solid phase microextraction (SPME) fiber coating for the extraction of polycyclic aromatic hydrocarbons (PAHs) from honey samples. The adsorbed PAHs were then analyzed by gas chromatography with mass spectrometric detection. The merits for the method include: (a) low limits of detection (0.06–0.17 ng/g, S/N = 3), (b) high enrichment factors (290-1566-fold), good reproducibility (relative standard deviations less than 8.4%) and excellent method recoveries for the PAHs (83.0%–116.0%). The enrichment performance of the COFs towards the PAHs could be attributed to the hydrophobic interaction, the high surface area and pore volume of the COF materials.

A New Green In Situ Effervescent CO2-Table-Induced Switchable Hydrophilicity Solvent Extraction Method of Rhodamine B in Food and Soft Drink Samples.

A new and simple effervescent CO2-table-induced switchable hydrophilicity solvent extraction method (CI-SHS) was used for the preconcentration of rhodamine B (RB). The main theme of the proposed method to disperse green solvent by in situ CO2-table system overcome on the contamination and to avoid the dispersion by using different chemicals. Switchable hydrophilicity solvent (N, N-Dimethyl cyclohexylamine) was dispersed in an aqueous solution by reaction of CO2-table of sodium carbonate and citric acid to enhance the contact area between two medium, which radically improved the extraction capacity of the RB from aqueous medium to switchable solvent. The phase separation was achieved by simple heating not by centrifugation that makes a change on hydrophilicity to hydrophobicity. The supernatant-enriched RB- N, N-Dimethyl cyclohexylamine phase was withdrawn and injected into the UV glass cells. The absorbance was measured at 542. Limit of detection and enhancement factor were achieved to be 0.042 and 50 µg/L. Validity and accuracy of the method verified by analysis of real samples by the spiking addition method. The relative standard deviation was obtained at 3.2%. The method was applied to food and soft drink samples. This method offers high sensitivity, selectivity, accuracy, and precision for the separation, preconcentration, and spectrophotometric determination of RB. Simple, fast, low-cost, and green extraction method was developed. High enrichment factor and lower detection limits were observed in this microextraction method. Present method is sensitive, selective, very accurate, and precise.

Corncob biochar as a coating for trace analysis of polycyclic aromatic hydrocarbons in water samples by online in-tube solid-phase microextraction coupled to high performance liquid chromatography

Biochar materials have been focused on enormous attention in the fields of capacitance, catalysis, adsorption due to its renewability, abundant in content and widespread distribution. In this work, corncob biochar materials were prepared under different carbonized temperature and characterized by scanning electron microscopy and Raman spectroscopy for surface morphology and graphitization degree. Then the materials were separately attached onto stainless steel wires as the coatings for solid-phase microextraction (SPME). Four wires with the same coating were placed into a polyetheretherketone tube to develop several extraction tubes. Coupled to high performance liquid chromatography (HPLC) with diode array detector (DAD), the tubes were evaluated using several polycyclic aromatic hydrocarbons (PAHs) as model analytes. According to the comparison of extraction efficiency, the best tube was selected. To achieve high sensitivity, both main extraction and desorption processes were optimized. Under the optimum conditions, an in-tube SPME-HPLC-DAD method for PAHs was established with low limits of detection (0.003–0.030 ng mL−1), wide linear ranges (0.010–15 ng mL−1, 0.017–15 ng mL−1, 0.033–15 ng mL−1 and 0.099–15 ng mL−1), high enrichment factors (1864–2615) and acceptable repeatability (relative standard deviations (RSDs, n = 3) less than 2.9% and 6.7% for intra-day and inter-day tests). Furthermore, the accuracy of the method was investigated via analyzing trace PAHs in real water samples and good recoveries (81.7%-116.8%) were obtained. In addition, the extraction tube exhibited satisfactory durability and chemical stability (RSDs ≤ 8.0%, n = 3) and acceptable reproducibility (RSD ≤ 7.8%, n = 3).

Thermal desorption sampling-gas chromatography-tandem mass spectrometry with a carbonyl-iron powder composite silica monolithic column for enrichment and determination of pyrethroid pesticide residues in tea samples

Long-term exposure to pyrethroid insecticides is detrimental to the nervous system, reproductive system, and immune system in humans. Therefore, enrichment detection of pyrethroid pesticides is imperative. In this study, a novel carbonyl-iron powder composite silica monolithic column was first prepared for the enrichment of pyrethroid pesticide residues in tea samples. Then, the target analytes were thermally desorbed and online-injected into a gas chromatography-tandem mass spectrometry (GC-MS/MS) system. In the present method, hydroxy-terminated polydimethylsiloxane (PDMS) was covalently bonded to the surface of the SiO2 network and subsequently bonded with the carbonyl-iron powder. After the target analytes were adsorbed and concentrated in the PDMS spots, high-frequency induction heating was used for GC-MS/MS sampling. Under the optimal conditions, the detection limits of the pyrethroid pesticide residues were 3.8 to 7.5 μg/kg, and the relative standard deviation was 3.2% to 6.8% (n=6). The extraction recovery ranged from 97.7% to 110.5%, and the correlation coefficient was ≥ 0.9960. In addition, the enrichment factor could reach 1000 times. PDMS materials show excellent adsorption properties for non-polar solutes. In our experiment, carbonyl iron powder-bonded monolithic columns were prepared on the basis of stir bar sorptive extraction (SBSE). Carbonyl iron powder magnetic particles were evenly implanted into the inorganic-organic hybrid cassia material for realizing rapid and uniform desorption upon electromagnetic induction heating. Under the premise of perfectly integrating the technical advantages of SBSE and solid-phase microextraction (SPME), the electromagnetic induction characteristics of carbonyl iron powder can be exploited for thermal desorption and directly combined with GC-MS to facilitate online analysis and solvent-free elution. Compared with the conventional SPME method, the proposed method has the advantages of high enrichment factor, large adsorption capacity of the column, reusability, high degree of automation, and good universality. This method has high significance for sample preparation and for the extraction of pesticide residues in complex matrices.

Preparation of magnetized polycaprolactone composite and its use in stirring–dependent magnetic dispersive solid phase extraction combined with dispersive liquid–liquid microextraction

In present work, a ball milling procedure has been used for chemical synthesis–free and facile preparation of magnetized polycaprolactone composite in which the natural iron oxide obtained from sand, which is easy–accessible and low cost, was used as the magnetic core. The prepared composite was employed for the extraction of some pesticides (diazinon, metalaxyl, oxadiazon, bromopropylate, and fenazaquin) from fruit juice and herbal distillate samples in the developed method named stirring–dependent magnetic dispersive solid phase extraction. In the following, a dispersive liquid–liquid microextraction method was done to enrich the extracted pesticides and obtain high sensitivity. To do the extraction procedure, a few mg of the composite is added into an aqueous phase containing the analytes and stirred at high rate. By this action the particles of composite are dispersed in whole parts of the sample solution and adsorb the analytes. After a few minutes the agitation is stopped and the composite particles are collected on the magnetic stir bar which is taken and eluted with methanol to desorb the analytes. Then the eluent is taken, mixed with 1,1,2-trichloroethane at µL–level, and rapidly injected into deionized water. The obtained cloudy solution is centrifuged and an aliquot of the sedimented phase containing the extracted analytes is injected into gas chromatography–flame ionization detection. Under optimized conditions, the introduced method provided high enrichment factors (2280–2840), and low limits of detection (0.10–0.25 ng mL−1) and quantification (0.34–0.83 ng mL−1).

Sample Enrichment for Microchip Electrophoresis by Extraction Induced by Phase Separation of Aqueous Ionic Liquids

The phase separation of an aqueous ionic liquid in migration by electrophoresis was utilized for online sample enrichment in microchip electrophoresis. The enrichment of rhodamine 6G in a sample solution was examined to validate the present concept. The peaks of the dye in the electropherograms became sharper and more intense after phase separation in migrating than without phase separation. Optimizing the operating conditions should enable highly target-selective sample enrichment with a higher enrichment factor under microflows.

Magnetic nanoparticle-assisted in situ ionic liquid dispersive liquid-liquid microextraction of pyrethroid pesticides in urine samples

Dispersive liquid–liquid microextraction (DLLME) based on Fe3O4 magnetic nanoparticle-assisted in situ ionic liquid was developed as a novel method for the pretreatment of pyrethroid pesticides (flumethrin, bifenthrin and silafluofen) in urine samples. [N4,4,4,4]Cl and Na[N(CN)2] formed a ionic liquid ([N4,4,4,4][N(CN)2]), which provides an alternative to highly toxic solvents; moreover, high extraction recoveries and enrichment factors were achieved. The extraction parameters affecting the extraction recoveries were investigated. Under optimum conditions, the analytical method showed a good linear response, with correlation coefficient (R2) values ranging from 0.9994 to 0.9996. The enrichment factor, limit of detection and recovery were 108–125, 2.7–5.0 μg L−1 and 88.0–101.1%, respectively. Therefore, this green and simple method is suitable for the microextraction of pyrethroid pesticides in urine samples. It is valuable to establish a sensitive method for monitoring trace levels of pyrethroids, which could contribute to the use of rapid and green sample preparation procedures in urine samples.