Preparation and characterization of novel crown ether functionalized ionic liquid-based solid-phase microextraction coatings by sol–gel technology

Magnetic Graphene Dispersive Solid-Phase Extraction for the Determination of Phthalic Acid Esters in Flavoring Essences by Gas Chromatography Tandem Mass Spectrometry

In the present study, a sensitive, efficient and repeatable method for the simultaneous extraction and determination of 13 types of phthalic acid esters (PAEs) in flavoring essence samples using magnetic graphene solid-phase extraction coupled with gas chromatography tandem mass spectrometry was developed. Due to the unique structure of magnetic graphene, it has several advantages, such as large surface area and fast separation ability. This unique structure not only provided strong magnetic responsiveness for the separation but also prevented the self-aggregation of graphene. The large delocalized p-electron system of graphene can form strong π-stacking interactions with the benzene ring. Thus, graphene may be also a good candidate adsorbent for the adsorption of benzenoid-form compounds. Several magnetic soild-phase extraction parameters, such as elution solvents, amounts of sorbents, enrichment time and desorption time were optimized. The optimized procedures for this method were performed by ultrasonication using ethyl acetate as elution solvent for 5 min. Under the optimal conditions, the developed method provided spiked recoveries of 75.0–105.3% with relative standard deviations of ~5.6% and limits of detection were 0.011–0.091 mg/kg. Good linear relationships were observed with the coefficient of determination (R2) > 0.993 for all the analytes. Finally, the validated method was successfully applied to the analysis of PAEs in real samples.

Simultaneous determination of five organophosphorus pesticide residues in different food samples by solid-phase microextraction fibers coupled with high-performance liquid chromatography

BACKGROUND

Excessive or improper use of organophosphorus pesticides (OPPs) may adversely affect human health through the food chain. In the present study, a simple, rapid and effective analytical method was successfully established and used for the determination of OPPs quinalphos and its analogs in different food samples.

RESULTS

Under the optimized experimental conditions, five OPPs (quinalphos, triazophos, parathion, fenthion and chlorpyrifos-methyl) exhibit a good linearity within a range of 0.02 to 2.0 μg mL^-1 . The detection limit range was 3.0 to 10.0 μg L^-1 (signal-to-noise ratio = 3). The method was successfully used to detect and quantify the residues of quinalphos and its analogs in tomato, cabbage, barley and water samples; all spiked samples gave satisfactory recovery rates for the target analytes of between 82% and 98%, with a relative SD of 3.6% to 7.8%.

CONCLUSION

The results obtained show that the proposed method is an accurate, rapid and reliable sample pre-treatment method with respect to giving a good enrichment factor and detection limit for determining quinalphos pesticide residues in different food samples. © 2019 Society of Chemical Industry.

Solvate and protic ionic liquids from aza-crown ethers: synthesis, thermal properties, and LCST behavior

In recent years, solvate and protic ionic liquids (ILs) have attracted much attention. We synthesized both types of ILs from alkyl aza-crown ethers (L = N-propyl-1-aza-15-crown-5 (L¹) and N-C₆F₁₃C₂H₄-1-aza-15-crown-5 (L²)). The solvate ILs [ML][Tf₂N] (M = Na⁺, K⁺) were solids (T_m = 58-68 °C), whereas the solvate ILs [ML][Tf₂N] (M = Li⁺, Ag⁺) and protic ILs [HL][Tf₂N] were liquids with low glass transition temperatures. The ILs containing Na ions were more crystalline and exhibited higher melting points than the other ILs. The decomposition temperatures of the protic ILs were higher than those of the solvate ILs. A protic IL with a paramagnetic anion, [HL¹][FeCl₄] (T_m = 70.5 °C), was also synthesized and its crystal structure was determined. The solvate ILs [NaL²][X] (X = Cl^-, CF₃CO₂^-, TsO^-, PhSO₃^-) exhibited a lower critical solution temperature (LCST)-type behavior in water. The effects of salt addition on the LCST of L² were also investigated. The LCST of these ILs generally increased with increasing hydrophilicity or basicity of the counter anion. This tendency, which is nearly opposite to that of ILs with quaternary onium cations, is ascribed to the amphiphilic nature of the cation. The corresponding protic ILs did not exhibit LCST behavior.

Amino acid-based ionic liquid surface modification of magnetic nanoparticles for the magnetic solid-phase extraction of heme proteins

Amino acid-based ionic liquid functionalized magnetic nanoparticles were fabricated as an MSPE adsorbent for hemoglobin with a binding capacity of 1.58 g g⁻¹.

Mesoporous TiO₂ nanoparticles for highly sensitive solid-phase microextraction of organochlorine pesticides

Mesoporous TiO2 nanoparticles were synthesized with the hydrothermal method and characterized by powder X-ray diffraction (PXRD) and transmission electron microscope (TEM). Then a superior solid-phase microextraction (SPME) fiber was fabricated by sequentially coating the stainless steel fiber with silicone sealant film and mesoporous TiO2 powder. The developed fiber possessed a homogeneous surface and a long life-span up to 100 times at direct immersing (DI) extraction mode. Under the optimized conditions, the extraction efficiencies of the self-made 17 μm TiO2 fiber for six organochlorine pesticides (OCPs) were higher than those of the two commercial fibers (65 μm PDMS/DVB and 85 μm PA fibers) which were much thicker than the former. As for analytical performance, low detection limits (0.08-0.60 ng L(-1)) and wide linearity (5-5000 ng L(-1)) were achieved under the optimal conditions. The repeatabilities (n=5) for single fiber were between 2.8 and 12.3%, while the reproducibilities (n=3) of fiber-to-fiber were in the range of 3.7-15.7%. The proposed fiber was successfully applied to the sensitive analysis of OCPs in real water samples and four of the six analytes were detected from the rainwater and the lake water samples.

Disposable ionic liquid-coated etched stainless steel fiber for headspace solid-phase microextraction of organophosphorus flame retardants from water samples

An ionic liquid-coated etched stainless steel fiber was prepared for solid-phase microextraction of organophosphorus flame retardants from water.

Anionic surfactant micelle-mediated extraction coupled with dispersive magnetic microextraction for the determination of phthalate esters

A novel and easy two-step microextraction technique combining anionic surfactant coacervation phase (CAP) extraction and dispersive microsolid-phase extraction (D-μ-SPE) was developed for the high-performance liquid chromatography-ultraviolet detection to determination of phthalate esters (PEs) in water samples. The method started with the phase separation of sodium dodecylbenzenesulfonic acid (SDBSA) obtained by adding NaCl, whereas the target analytes were extracted in the CAP. The CAP was then retrieved using diatomaceous earth-supported magnetite nanoparticles. The effects of solution acidity, SDBSA, and electrolyte concentration, extraction time, magnetic material quantity, and elution solvent volume were discussed. Under optimal extraction conditions, the extraction recoveries ranged from 48.6 to 84.8%, and relative standard deviations ranged from 3.9 to 5.7% (n = 10). The detection limits ranged from 0.5 to 5.0 ng mL(-1) for the five PEs. The proposed method was used to determine the five PEs in the water samples and recoveries between 85.7 and 105.5%.

Fe3O4@ionic liquid@methyl orange nanoparticles as a novel nano-adsorbent for magnetic solid-phase extraction of polycyclic aromatic hydrocarbons in environmental water samples

A novel nano-adsorbent, Fe3O4@ionic liquid@methyl orange nanoparticles (Fe3O4@IL@MO NPs), was prepared for magnetic solid-phase extraction (MSPE) of polycyclic aromatic hydrocarbons (PAHs) in environmental water samples. The Fe3O4@IL@MO NPs were synthesized by self-assembly of the ionic liquid 1-octadecyl-3-methylimidazolium bromide (C18mimBr) and methyl orange (MO) onto the surface of Fe3O4 silica magnetic nanoparticles, as confirmed by infrared spectroscopy, ultraviolet-visible spectroscopy and superconducting quantum interface device magnetometer. The extraction performance of Fe3O4@IL@MO NPs as a nano-adsorbent was evaluated by using five PAHs, fluorene (FLu), anthracene (AnT), pyrene (Pyr), benzo(a)anthracene (BaA) and benzo(a)pyrene (BaP) as model analytes. Under the optimum conditions, detection limits in the range of 0.1-2 ng/L were obtained by high performance liquid chromatography-fluorescence detection (HPLC-FLD). This method has been successfully applied for the determination of PAHs in environmental water samples by using the MSPE-HPLC-FLD. The recoveries for the five PAHs tested in spiked real water samples were in the range of 80.4-104.0% with relative standard deviations ranging from 2.3 to 4.9%.

Ionic liquids in microextraction techniques

The tremendous potential of room temperature ionic liquids as an alternative to environmentally harmful ordinary organic solvents is well recognized. Due to their unique properties, such as low volatility, tunable viscosity and miscibility, and electrolytic conductivity, ionic liquids have attracted extensive attention and gained popularity in many areas of analytical chemistry including modern sample preparation techniques. In this review the advantages and limitations of application of ionic liquids as solvents/sorbents for microextraction are critically discussed. Topics covered include solid-phase microextraction, single drop microextraction, dispersive liquid-liquid microextraction and hollow-fiber liquid-phase microextraction. The compatibility of the ionic liquid-based microextraction with different analytical techniques such as gas chromatography, high-performance liquid chromatography, electrothermal or flame atomic absorption spectrometry and some others is also discussed. Finally, the main practical applications on this topic are summarized.