Electrospun polycaprolactam-manganese oxide fiber for headspace-solid phase microextraction of phthalate esters in water samples

Electrospun mesh pattern of polyvinyl alcohol/zirconium-based metal-organic framework nanocomposite as a sorbent for extraction of phthalate esters

Herein, an electrospun composite polyvinyl alcohol/zirconium-based metal-organic frameworks (PVA@UiO-66) nanofiber coating was prepared on the surface of stainless steel mesh (SSM) and then utilized as novel sorbent for the extraction of phthalate esters (PEs) in milk and water samples. Gas chromatography equipped with a flame ionization detector (GC-FID) was used for the quantitative determination of extracted analytes. The SSM coated with PVA@UiO-66 was used in a polypropylene syringe to fabricate the solid-phase extraction (SPE) device. The PVA@UiO-66 nanofiber coating was confirmed using X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy analysis (FT-IR), and field emission scanning electron microscopy (FESEM). The effective parameters of the extraction efficiency including volume and type of desorption solvent, sample volume, ionic strength, pH, extraction flow rate, and desorption flow rate were optimized. At the optimal extraction conditions, the calibration plots for phthalate esters were linear within the range of 0.05-100 ng mL-1 and, low detection limits (0.015-0.06 ng mL-1). Finally, this semi-automated SPE was used for the extraction and detection of phthalate esters (PEs) in milk and various environmental real water samples. The results showed good precision with acceptable and satisfactory extraction recovery values ranging from 89.5 to 99.2% and relative standard deviations (RSDs%) ranging from 4.5 to 6.9%.

A Review of the Analysis of Phthalates by Gas Chromatography in Aqueous and Food Matrices

As a commonly well-known industrial chemical, phthalates are produced in high volumes to be used in various consumer products (e.g., plasticizers, medical devices, construction materials, and toys) to enhance softness, durability, transparency, and flexibility. Phthalates are generally not chemically bonded to the polymer chain of the plastic in which they are mixed. Thus, they may leach, migrate, or evaporate into indoor/outdoor air, and foodstuffs. In this review, a comprehensive overview of several sample preparation methods coupled with gas chromatography for the analysis of phthalates in various kinds of complex matrices, with a focus on the last 20 years' worth of papers. The review begins by highlighting the environmental significance of phthalate pollution along with the various routes to their exposure to general population. Then, the discussion is extended to cover the pretreatment and extraction techniques for phthalates for their quantitation based on gas chromatographic approach. Finally, the present and future challenges for the detection of phthalates in aqueous and food matrices are discussed.

Confinement effect of ionic liquid: Improve of the extraction performance of parent metal organic framework for phthalates

In order to better identify the hazards of pollutants, developing the analytical methods that can sensitively detect and precisely monitor the content of trace pollutants has been the constant pursuit. In this paper, a new solid phase microextraction coating-ionic liquid/metal organic framework (IL/MOF) was obtained through the IL-induced strategy and used for the solid phase microextraction (SPME) process. IL was introduced into metal-organic framework (MOF) cage based on the anion of ionic liquid could interact strongly with the zirconium nodes of UiO-66-NH₂. The introduction of IL not only increased the stability of composite, the hydrophobicity of IL also changed the environment of MOF channel, providing the hydrophobic effect to the targets. The confinement effect of IL effectively improved the extraction performance of parent MOF and the extraction performance of synthesized IL/UiO-66-NH₂ for phthalates (PAEs) were 1.3-3.0 times that of parent UiO-66-NH₂. Thanks to the strong interaction force (hydrogen bonding interaction, π-π stacking, hydrophobic interaction force), the IL/UiO-66-NH₂-coated fiber coupled with gas chromatography-mass spectrometer showed a wide linear ranges (1-5000 ng L^-1) with good correlation (R², 0.9855-0.9987), lower detection limit (0.2-0.4 ng L^-1) and satisfactory recoveries (95.3-119.3%) for PAEs. This article is dedicated to provide another way to improve the extraction performance of material.

In Situ Synthetic ZIF-8/Carbon Aerogel Composites as Solid-Phase Microextraction Coating for the Detection of Phthalic Acid Esters in Water Samples

In this study, a hybrid composite featuring zeolitic imidazolate framework-8/carbon aerogel (ZIF-8/CA) was synthesized via in situ nucleation and growth of ZIF-8 nanoparticles inside carbon aerogels. The novel material was used as the solid-phase microextraction (SPME) coating for the five phthalic acid esters (PAEs) detection by coupling with a gas chromatography–flame ionization detector (GC-FID). Compared with bare carbon aerogel, the ZIF-8/CA presented the best performance, which is attributed to the unique advantages between the high surface area of CA and high hydrophobic properties, the thermal stability of ZIF-8, and their synergistic adsorption effects, such as molecular penetration, hydrogen bond, and π–π stacking interactions. Under the optimized conditions, the as-proposed ZIF-8/CA fiber provided a wide linearity range from 0.2 to 1000 μg L⁻¹ and a low detection limit of 0.17–0.48 μg L⁻¹ for PAEs analysis. The intra-day and inter-day of signal fiber and the fiber–fiber relative standard deviations were observed in the ranges of 3.50–8.16%, 5.02–10.57%, and 5.66–12.11%, respectively. The method was applied to the determination of five PAEs in plastic bottled and river water samples.

Superhydrophobic Nanosilica Decorated Electrospun Polyethylene Terephthalate Nanofibers for Headspace Solid Phase Microextraction of 16 Organochlorine Pesticides in Environmental Water Samples

A new solid phase micro extraction (SPME) fiber coating composed of electrospun polyethylene terephthalate (PET) nanofibrous mat doped with superhydrophobic nanosilica (SiO2) was coated on a stainless-steel wire without the need of a binder. The coating was characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectrometer (FTIR) techniques and it was used in headspace-SPME of 16 organochlorine pesticides in water samples prior to gass chromatography micro electron capture detector (GC-µECD) analysis. The effects of main factors such as adsorption composition, electrospinning flow rate, salt concentration, extraction temperature, extraction time, and desorption conditions were investigated. Under the optimum conditions, the linear dynamic range (8−1000 ng L−1, R2 > 0.9907), limits of detection (3−80 ng L−1), limits of quantification (8−200 ng L−1), intra-day and inter-day precisions (at 400 and 1000 ng L−1, 1.7−13.8%), and fiber-to-fiber reproducibility (2.4−13.4%) were evaluated. The analysis of spiked tap, sewage, industrial, and mineral water samples for the determination of the analytes resulted in satisfactory relative recoveries (78−120%).

Electrospun Membrane for the Extraction of Acrylamide in Pet Food Samples

A simple microextraction procedure was developed using an electrospun nanostructured membrane to determine acrylamide in pet food samples. Polyvinyl chloride, polyvinyl alcohol, and polyvinyl alcohol/hydroxyethyl cellulose electrospun membranes were prepared and investigated as a sorbent to extract acrylamide. The characterization of the synthesized electrospun membrane was accomplished using field-emission scanning electron microscopy (FESEM). FESEM images showed uniform morphology and beadless nanofibers. Quantification was done by high-performance liquid chromatography with ultraviolet detection. A series of microextraction parameters were optimized before quantitative analysis of dry pet food samples. The calibration curve exhibited good linearity with a correlation coefficient of 0.996 across a 1–100 μg/kg concentration range. The recovery of acrylamide for pet food samples spiked with 5 and 10 μg/kg was in the range of 79.6–113.9 (n = 3). The intraday precision of the method was less than 12% for three replicated real spiked samples at the 5 μg/kg level. The results demonstrated that the electrospun nanostructured membrane has good extraction selectivity and minimal matrix effect with an enrichment factor of 180-fold.

Electrochemically controlled solid phase microextraction based on a conductive polyaniline-graphene oxide nanocomposite for extraction of tetracyclines in milk and water

BACKGROUND

Tetracycline antibiotics are employed for human and animal health and for speeding up growth rates. However, their presence in food products and environmental waters has been a concern for some years. Therefore, a variety of sample preparation methods have been developed for the analysis of tetracycline residues in these matrices.

RESULTS

An electrochemically controlled solid phase microextraction based on a modified copper electrode with polyaniline/graphene oxide (PANI/GO) conductive nanocomposite was developed for the extraction of oxytetracycline, tetracycline and doxycycline before high-performance liquid chromatography-UV analysis. PANI/GO was synthesized by in situ chemical oxidative polymerization, characterized by scanning electron microscopy and Fourier-transform infrared spectroscopy, and bound on the electrode using high purity conductive double-sided adhesive carbon glue. The significant factors affecting the performance of microextraction were investigated and optimized. Under the optimized conditions [sample, 15 mL; sorbent, 10 mg; pH, 3.0; electroextraction voltage, -0.9 V; electroextraction time, 20 min; eluent (MeOH/NH₃ ), 500 μL; and desorption time, 5 min], the limits of detection for target analytes were in the ranges 0.32-1.01 and 2.42-7.59 μg L^-1 in water and milk samples, respectively. The linear ranges were 1.06-750 μg L^-1 for water and 8.05-750 μg L^-1 for milk samples. The intra-day and inter-day precisions were 2.32-3.80 and 3.29-4.25, respectively. The method was applied to the determination of analytes in milk and water samples with different fat contents, and the recoveries were obtained in the range 71-104%.

CONCLUSION

The developed electro-microextraction method provides a facile, rapid, cost-effective, sensitive and efficient promising procedure for the extraction of antibiotics in complex matrices. © 2020 Society of Chemical Industry.

Efficient photocatalytic removal of phthalates easily implemented over a bi-functional {001}TiO2 surface

It is stubborn to remove the lowly concentrated phthalic acid esters (PAEs) that usually coexist with other highly concentrated but low-toxic pollutants in municipal sewage. Herein, we report a novel strategy for completely removing the PAEs over a bi-functional {001}TiO₂ surface (with highly exposed {001} facet), which not only serve as functional sites to specifically adsorb the target PAEs pollutants, but also contribute to an enhanced oxidation ability. The adsorption behavior of PAEs on {001}TiO₂ is analyzed deeply through kinetic experiments combining with in situ ATR-FTIR spectroscopy and theoretical calculations. The results reveal that the adsorption capacities of PAEs on {001}TiO₂ are about 4-5 times higher than that on TiO₂, both of which follow the pseudo-second-order and Langmuir model. This is mainly attributed to the interfacial Lewis Acid-Base Pair between {001} facet Ti_5c sites and CO of PAEs. Benefitting from the specific adsorption capability toward target pollutant and enhanced oxidation ability of {001} facets, nearly 100% of DMP or DEP in simulated wastewater can be eliminated by {001}TiO₂ within 2 h illumination, and the relevant degradation rate constants (k) (3.67 h^-1 for DMP and 2.19 h^-1 for DEP) are 5.73 and 3.08 folds higher than that of pure TiO₂, respectively. In the application of municipal wastewater, nearly 76% of DMP and 85% DEP can be eliminated by {001}TiO₂ within 2 h illumination, which are nearly 3-6 fold higher than that of pure TiO₂.

Monitoring of priority pollutants chlorophenols in water and milk by headspace solid-phase microextraction based on electrospun polycaprolactam nanofibers decorated with cadmium oxide-carbon nanotubes

Priority pollutants chlorophenols are broadly used chemicals that are persistent in the environment and causing serious human health hazards. The current study introduces a novel adsorbent for the extraction of chlorophenols from river water, surface water, and milk by headspace solid-phase microextraction coupled with gas chromatography. The adsorbent composite was prepared by blending polycaprolactam (nylon-6) mat and newly synthesized carbon nanotubes decorated with cadmium oxide nanoparticles followed by electrospinning technique to produce based nanofiber. The proposed nanofiber was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction techniques. The main parameters that affect extraction efficiency, including ionic strength, extraction time, desorption time, and extraction temperature, were investigated and optimized. The linear range was 0.05-5 ng/mL; the limits of detection (signal/noise=3) were 0.02-0.04 ng/mL. The relative recoveries for real samples (river water, surface water, and milk) were in the range of 84-114%.

Analytical methods to analyze pesticides and herbicides

Presented in this paper is an annual review of literatures published in 2018 on topics relating to analytical methods for pesticides and herbicides. According to the different techniques, this review is divided into six sections, including extraction methods; chromatographic or mass spectrometric techniques; electrochemical techniques; spectrophotometric techniques; chemiluminescence and fluorescence methods; and biochemical assays. PRACTITIONER POINTS: Totally 134 relevant research articles are summarized. The review is divided into six parts according to the techniques. Chromatographic and mass spectrometric methods are the most widely used.

A miniature stainless steel net dumbbell-shaped stir-bar for the extraction of phthalate esters in instant noodle and rice soup samples

This work reports the development of a very-simple-to-construct stir-bar extraction device so called "a dumbbell-shaped stainless steel stir-bar." The extraction device was assembled from a rolled up stainless steel net filled with an XAD-2 sorbent and a metal rod to allow the use of a magnetic stirrer during extraction. The dumbbell-shaped stainless steel stir-bar was used to extract diethyl phthalate (DEP), dibutyl phthalate (DBP), and di(2-ethylhexyl) phthalate (DEHP) before analysis by a gas chromatograph equipped with an electron capture detector (GD-ECD). Under the optimal conditions, the developed method provided a good linearity from 10.0 to 1,000.0 ng mL^-1 for all three compounds. Limits of detection and limits of quantification were 9.37 ± 0.29 ng mL^-1 and 31.22 ± 0.95 ng mL^-1 for DEP, 5.73 ± 0.31 ng mL^-1 and 19.1 ± 1.0 ng mL^-1 for DBP and 3.30 ± 0.06 ng mL^-1 and 11.0 ± 0.19 ng mL^-1 for DEHP, respectively. Good recoveries in the range of 81.89 ± 0.17 to 109.5 ± 2.0% were achieved when the method was used to extract phthalate esters in five instant noodle and two rice soup samples.

Electrospun polymer composite nanofiber-based in-syringe solid phase extraction in tandem with dispersive liquid-liquid microextraction coupled with HPLC-FD for determination of aflatoxins in soybean

A fast method based on in-syringe solid phase extraction combined with dispersive liquid-liquid microextraction was developed for extraction of aflatoxins prior to HPLC-FD. Electrospun polyurethane nanofibers doped with graphene oxide were collected on a thin metal net sheet without using a binder, placed into a filter holder between filter papers on a syringe tip and used as an efficient adsorbent for the first time. The major parameters affecting whole extraction efficiency were investigated and optimized. Under the optimum conditions, the limits of detection and the limits of quantification were in the range of 0.09-0.15 and 0.3-0.5 µg kg-1, respectively. The linear dynamic range was 0.3-1000 µg kg-1 with determination coefficients of 0.9946-0.9965. The inter- and intra-day precisions were lower than 4.3 and 7.2%, respectively. The method was successfully applied for the determination of aflatoxins B1, B2, G1, and G2 in soybeans and satisfactory relative recoveries of 76-101% were achieved.

Self-Assembling Hydrophilic Magnetic Covalent Organic Framework Nanospheres as a Novel Matrix for Phthalate Ester Recognition

The development of covalent organic framework (COF)-derived materials with additional functions and applications is highly desired. In this work, a unique COF-functionalized hydrophilic magnetic nanosphere (Fe₃O₄@PDA@TbBd) with Fe₃O₄ as a magnetic core, polydopamine (PDA) as a hydrophilic middle layer, and TbBd as an outer COF shell was facilely prepared as a novel hydrophilic platform for efficient detection of phthalic acid esters (PAEs). The resultant Fe₃O₄@PDA@TbBd nanosphere displayed strong magnetic response, high surface area, and good hydrophilicity. Accordingly, the newly synthesized COF exhibited great potential in phthalate analysis with a wide linearity (50-8000 ng/mL), good recovery (92.3-98.9%), a low limit of detection (0.0025-0.01 ng/mL), and a small relative standard deviation (for intraday less than 4.6% and for interday less than 6.8%). More excitingly, the new COF was applied to analyze nine PAEs in the human plasma sample. This work opens up new avenues for the development and application of functionalized COF-derived materials.