Experimental and density functional theory studies during a new solid phase extraction of phenolic compounds from wastewater samples prior to GC–MS determination

Development of a vortex-assisted switchable-hydrophilicity solvent-based liquid phase microextraction for fast and reliable extraction of Zn (II), Fe (II), Pb (II), and Cd (II) from various baby food products

This manuscript describes the development of a novel liquid phase microextraction (LPME) method for the extraction and determination of Zn (II), Fe (II), Pb (II), and Cd (II) in various infant/baby food and supplements products. The method is based on vortex-assisted extraction combined with a switchable-hydrophilicity solvent (SHS) sample preparation. The SHS, which undergoes reversible phase changes triggered by pH change, enables selective extraction and easy phase separation. A flame atomic absorption spectroscopy was used in the final determination step. Optimization studies revealed, that the optimal pH of the sample solution (after digestion) during analytes extraction is 5.5. A l-proline is added to the sample (375 mM) to ensure the complexation of the target metal cations. After the complexation step, 750 µL of SHS - a N, N-Dimethylcyclohexylamine along with 0.9 mL of 2 M of acetic acid solution is added (hydrophilicity switch-on stage) and mixed manually to obtain a homogeneous solution. In the last stage, 0.45 mL of 10 M NaOH solution (hydrophilicity switch-off stage) is added to the sample solution and a vortex for 100 s is applied to ensure the effective extraction and separation of the complex containing the analytes. At this stage, a cloudy solution is immediately obtained. Finally, the effective phase separation is obtained at the centrifugation step (4000 rpm for 2 mins). The method limit of detection was as 0.03, 0.009, 0.6, and 0.2 ng/L for Zn (II), Fe (II), Cd (II), and Pb (II) respectively with RSD% below 2.0 %. The analysis of certified reference materials and real samples proved the full applicability of the method for routine analysis, contributing to the field of heavy metal analysis and ensuring the safety of baby products. According to the AGREE methodology, this method can be named as green analytical chemistry method with a score of 0.77.

Thiocarbamide conversion-based nitrogen-rich covalent organic framework coatings for electro-enhanced solid-phase microextraction of bisphenols

Design and preparation of fiber coatings with excellent electrochemical performance and high polarity is significant for efficient extraction of polar targets in electro-enhanced solid-phase microextraction (EE-SPME). In this work, a combination strategy for structure regulation of covalent organic framework (COF) was proposed to fabricate a nitrogen-rich thiocarbamide linked COF coating (Thiocarbamide-TZ-DHTP) via molecular design and post-synthetic thiocarbamide conversion. The prepared COF coating possesses a large number of O, N, and S functional groups, which not only endow the coating with higher polarity but also significantly enhance its electrochemical performance. The COF coating was used for EE-SPME of polar bisphenols (BPs), demonstrating excellent enrichment efficiency and durability. Subsequently, coupled with gas chromatography-tandem mass spectrometry (GC-MS/MS), a sensitive method was developed for determination of trace BPs. The established method possess wide linear ranges (2.0-800.0 ng L-1), good correlation coefficients (0.9985-0.9994) and low detection limits (0.1-2.0 ng L-1). Moreover, the established method had been successfully applied to detection of trace BPs in tea beverage with satisfactory recoveries (81.6 % to 118.6 %). This research provides a feasible pathway for preparing COF coating with excellent electrochemical performance and high polarity for EE-SPME.

Statistical physics modeling study of an environmentally friendly and efficient adsorbent derived from the brown macroalgae Bifurcaria bifurcata for the removal of Bisphenol A

The brown macroalgae Bifurcaria bifurcata was valued and used to develop a carbonaceous material activated by H2SO4 (AC-BB@H2SO4), with the goal of assessing its adsorption ability against Bisphenol A (BPA). During the adsorption experiments, the effects of the adsorbent dose, solution pH, and contact time were examined, and the results were m = 0.4 g/L, pH = 8.3, and t = 120 min, with an elimination yield of 91.6 %. With comparatively high R2 values, the pseudo-second-order kinetic model perfectly fitted the experimental data. Langmuir's model was found to be the best appropriate for describing the adsorption equilibrium of BPA on AC-BB@H2SO4. The thermodynamic findings show that BPA adsorption on AC-BB@H2SO4 was spontaneous, favorable, and endothermic in nature. Even after six cycles of reuse, regeneration testing demonstrated that our adsorbent could eliminate BPA by >50 %. The BPA adsorption mechanism's statistical physics control parameters were determined and analyzed. BPA's adsorption energies were <40 kJ/mol, indicating that the interactions between BPA and AC-BB@H2SO4 were governed by physical forces (i.e., hydrogen bonding and van der Waals and electrostatic interactions). All of these intriguing findings indicate that our carbonaceous material might have direct ramifications in the field of wastewater treatment, notably for the clearance of BPA, which is difficult to biodegrade.

In-situ formation of CO2-incorportaed solid sorbent for dispersive solid phase extraction of phenolic compounds from water and wastewater samples prior to gas chromatography-flame ionization detector

BACKGROUND

Herein, a new extraction procedure based on in-situ formation of carbon dioxide-incorporated solid sorbent was introduced for dispersive solid phase extraction of phenolic compounds from aqueous samples. In this study, incorporation of carbon dioxide into the structure of a diamine led to the formation of a solid compound in the sample solution that adsorbed the analytes.

RESULTS

The sample solution was mixed with isophorone diamine and placed under carbon dioxide stream. By doing so, isophorone diamine reacted with carbon dioxide and produced a carbamic acid analogue. It was dispersed into the sample solution as tiny particles that adsorbed the analytes. The adsorbed analytes were eluted by a volatile organic solvent and concentrated more by the vaporization of the eluate. The extraction procedure was done at low temperature to limit the releasing carbon dioxide from the produced compound. To obtain the reliable results, the method was validated and the obtained limits of detection and quantification were in the ranges of 0.29-41 and 0.96-1.3 ng/mL, respectively. Acceptable relative standard deviation (≤7.3%) and coefficient of determination (≥0.994) values confirmed the method repeatability and linearity. High enrichment factors (410-435) and extraction recoveries (82-87%) were attained with the introduced method.

SIGNIFICANCE AND NOVELTY

In this work, a chemical reaction was done between isophorone diamine and carbon dioxide in solution. The produced product (sorbent) was insoluble in solution and dispersed in whole parts of the solution as tiny particles. A high contact area between the sorbent and analytes provided high extraction efficiency for the analytes. The method was successful utilized in determining target analytes in real samples and the matrix effect of the samples had no important effect on the obtained results.

A green hydrophobic deep eutectic solvent for extraction of phenol from aqueous phase

Deep eutectic solvents (DESs), have been recognized as effective materials for the extraction of different compounds. In this study, the performance of a novel hydrophobic DES was evaluated for the extraction of phenol from aqueous solutions. Octanoic and dodecanoic fatty acid precursors with a definite molar ratio of 3:1, respectively, were used for the DES having a low melting point of 8.3 °C. The purity and stability of the product were confirmed via characterizing by FTIR, 1H and 13C NMR methods. The liquid-liquid equilibrium of the water + phenol + DES ternary system at different temperatures of 293.2, 298.2 and 308.2 K was accordingly studied through cloud point titration method and refractive index measurement. Interestingly, the important parameters of the solute distribution coefficient and the separation factor were, respectively, within the high levels of (6.8321-9.7787) and (895.76-2770.17), indicating the amazing capability of the DES. Reasonably, both of these parameters decreased with temperature. The NRTL and UNIQUAC thermodynamic models were employed to reproduce the obtained tie-lines and to determine the interaction parameters at each temperature. The low level root mean square deviations for the mentioned models were, respectively, within (0.0014-0.0027) and (0.0045-0.0063); confirming satisfactorily agreement with the experimental data.

Determination of Parabens and Phenolic Compounds in Dairy Products through the Use of a Two-Step Continuous SPE System Including an Enhanced Matrix Removal Sorbent in Combination with UHPLC-MS/MS

Dairy products can be contaminated by parabens and phenolic compounds from a vast variety of sources, such as packaging and manufacturing processes, or livestock through feed and environmental water. A two-step continuous solid-phase extraction (SPE) and purification methodology was developed here for the determination of both types of compounds. In the first step, a sample extract is passed in sequence through an EMR-lipid sorbent and an Oasis PRiME HBL sorbent to remove fat and preconcentrate the analytes for subsequent detection and quantification by UHPLC-MS/MS. This method enabled the determination of 28 parabens and phenolic contaminant with excellent recovery (91-105%) thanks to the SPE sorbent combination used. The proposed method was validated through the determination of the target compounds, and was found to provide low detection limits (1-20 ng/kg) with only slight matrix effects (0-10%). It was used to analyse 32 different samples of dairy products with different packaging materials. Bisphenol A and bisphenol Z were the two phenolic compounds quantified in the largest number of samples, at concentrations over the range of 24-580 ng/kg, which did not exceed the limit set by European regulations. On the other hand, ethylparaben was the paraben found at the highest levels (33-470 ng/kg).

Rapid extraction of BTEX in water and milk samples based on functionalized multi-walled carbon nanotubes by dispersive homogenized-micro-solid phase extraction

An advanced synthesis based on the phenylalanine (Phe) and task-specific ionic liquid (TSIL) functionalized on multi-walled carbon nanotubes (Phe/TSIL@MWCNTs), was used to extract benzene, ethylbenzene, toluene, and xylene (BTEX) from cow's milk, powdered milk, and farm water samples. The BTEX was efficiently extracted by ultrasound-assisted dispersive homogenized-micro-solid phase extraction (USA-DH-µ-SPE) between 95.1% and 103.4%. By procedure, 50 mg of Phe/TSIL@MWCNTs was added to 0.2 mL of acetone and injected into 10 mL of the samples. The upper aqueous solution was vacuumed, the vial heated to 80 °C, and the BTEX desorbed in the vial. Then, using a Hamilton syringe, 1-20 µL of gas in the headspace vial was determined by injecting it into the gas chromatography with flame ionization detection (GC-FID). The linear range, LOD, and LOQ for BTEX in milk and water samples were obtained at 0.05-500 µg L^-1, 15 ng L^-1, and 50 ng L^-1, respectively (r = 0.9997, RSD% = 2.27).

An immobilization of aminopropyl trimethoxysilane-phenanthrene carbaldehyde on graphene oxide for toluene extraction and separation in water samples

A new functionalized Nano graphene with aminopropyl trimethoxysilane-phenanthrene-4-carbaldehyde (NGO@APTMS-PNTCA) as a novel adsorbent was used to extract toluene from water samples by the ultrasound-assisted dispersive solid-phase microextraction procedure (USA-D-SPME). So, 50 mg of NGO@APTMS-PNTCA adsorbent was added to water samples and sonicated for 20 min. After toluene extraction, the NGO@APTMS-PNTCA adsorbent separated from the liquid phase with a Whatman membrane filter (200 nm). Then, the toluene was back-extracted from the adsorbent by 2.0 mL of the acetone/ethanol (1:1, eluent) at 25 °C. Due to the physical properties and structure of toluene, fluorobenzene was used as an internal standard. Finally, the toluene values were measured by a gas chromatography-flame ionization detector (GC-FID). In optimized conditions, the limit of detection (LOD), the working range (WR), and the enrichment factor (EF) were obtained at 2.5 μg L^-1, 0.01-1.2 mg L^-1, and 9.63, respectively (MRSD% = 3.38). Also, the limit of quantification (LOQ) 10 μg L^-1 and extraction recovery of more than 95% was efficiently achieved for toluene. Standard additions of toluene to blank solutions had high recoveries between 95.2% and 104.5% with a relative standard deviation (RSD%) of 0.27-5.2. The absorption capacities of NGO and NGO@APTMS-PNTCA adsorbents for toluene extraction were obtained at 32.8 mg g^-1 and 154.9 mg g^-1, respectively. The USA-D-SPME method was validated by spiking the standard concentrations of toluene. The proposed method demonstrated relevant and suitable statistical results with high accuracy and precision for toluene extraction by a novel adsorbent synthesis.

Simultaneous determination of volatile phenol, cyanide, anionic surfactant, and ammonia nitrogen in drinking water by a continuous flow analyzer

This study developed a method for the simultaneous determination of volatile phenol, cyanide, anionic surfactant, and ammonia nitrogen in drinking water, using a continuous flow analyzer. The samples were first distilled at 145 °C. The phenol in the distillate then subsequently reacted with alkaline ferricyanide and 4-aminoantipyrine to form a red complex that was measured colorimetrically at 505 nm. Cyanide in the distillate subsequently reacted with chloramine T to form cyanogen chloride, which then formed a blue complex with pyridinecarboxylic acid that was measured colorimetrically at 630 nm. The anionic surfactant reacted with basic methylene blue to form a compound that was extracted into chloroform and washed with acidic methylene blue to remove interfering substances. The blue compound in chloroform was determined colorimetrically at 660 nm. Ammonia reacted with salicylate and chlorine from dichloroisocyanuric acid to produce indophenol blue at 37 °C in an alkaline environment that was measured at 660 nm. The relative standard deviations were 0.75-6.10% and 0.36-5.41%, respectively, and the recoveries were 96.2-103.6% and 96.0-102.4% when the mass concentration of volatile phenol and cyanide was in the range of 2-100 μg/L. The linear correlation coefficients were ≥ 0.9999, and the detection limits were1.2 μg/L and 0.9 μg/L, respectively. The relative standard deviations were 0.27-4.86% and 0.33-5.39%, and the recoveries were 93.7-107.0% and 94.4-101.7%. When the mass concentration of anionic surfactant and ammonia nitrogen was 10-1000 μg/L. The linear correlation coefficients were 0.9995 and 0.9999, and the detection limits were 10.7 μg/L and 7.3 μg/L, respectively. When compared to the national standard method, no statistically significant difference was found. This approach saves time and labor, has a lower detection limit, higher precision and accuracy, less contamination, and is more appropriate for the analysis and determination of large-volume samples.

Facile fabrication of hydroxyl-functionalized hypercrosslinked polymer for sensitive determination of chlorophenols

Three hydroxyl-functionalized hypercrosslinked polymers (HCP-POL, HCP-HQ and HCP-PG) were synthesized by Friedel-Crafts reaction. The HCP-HQ displayed the largest surface area and highest adsorption capacity for chlorophenols (CPs). Thus, the HCP-HQ was further modified with magnetism to obtain M-HCP-HQ. An efficient magnetic solid-phase extraction method with M-HCP-HQ as adsorbent was developed for the first time to simultaneously extract four CPs from water and honey samples before analysis by high performance liquid chromatography-diode array detection. Under optimized conditions, the low detection limits (S/N = 3) were obtained to be 0.06-0.10 ng mL^-1 for water and 0.80-1.75 ng g^-1 for honey. The method recovery was 80.7%-119%, with relative standard deviations below 9.5%. The enrichment factors of the CPs were in the range of 57-220. The extraction mechanism could be attributed to the strong polar interaction, hydrogen bonding and π-π interactions between the M-HCP-HQ and CPs. The M-HCP-HQ based method can be served as a reliable and sensitive tool for detection CPs in water and honey samples.

Dual-spectrum online monitoring of puerarin and total flavonoids contents during the extraction process of Pueraria lobata

In the extraction process of traditional Chinese medicine (TCM), the rapid detection of the active components of TCM plays a vital role. We pioneered the choice of dual-spectrum technology based on near-infrared (NIR) and ultraviolet-visible (UV-Vis) spectra and applied it to the quantitative monitoring of online extraction of puerarin and total flavonoids from Pueraria lobata. An online monitoring system was constructed to fulfill the dual-spectrum online monitoring. The extraction solution flows from a flask into a pipeline under the control of a peristaltic pump, removing the solid residues contained in the solution with filters. When the extraction solution flows into the cuvette, it will be measured with NIR and UV-Vis portable spectrometers. After finishing the spectra collection, the peristaltic pump will reverse to push the extraction solution back to the flask. The partial least squares (PLS) models were established to quantitatively analyze puerarin and total flavonoids by NIR, UV-Vis, and dual-spectrum data. As for NIR, UV-Vis and dual-spectrum, the RMSEP (mg/mL) of the puerarin models were 0.0803, 0.0500, and 0.0351, and those of the total flavonoids models were 0.4373, 0.2402, and 0.1795, respectively. The results show that the dual-spectrum online monitoring system is simple, stable and fast (a few seconds) in operation, and accurate in prediction. Compared with individual NIR or UV-Vis spectra, the dual-spectra contains more comprehensive information, and the prediction ability is stronger. This method is expected to become a promising tool for the quantitative analysis of other traditional Chinese medicines.

Response surface optimization of a vortex-assisted dispersive liquid-liquid microextraction method for highly sensitive determination of repaglinide in environmental water by HPLC/UV

A vortex-assisted dispersive liquid–liquid microextraction (DLLME) method, mated to chemometrics and combined with HPLC/UV detection was optimized and validated for enrichment and determination of repaglinide in environmental samples using nateglinide as an internal standard (IS). A phosphate buffer (10 mM, pH 2.5): acetonitrile (45:55, v/v) was used as a mobile phase with a flow rate of 1 mL/min in an isocratic elution mode. Chemometrics-assisted optimization was performed using a quadratic integrated d-optimal design. The developed model assessed the statistical significance of the independent variables and their interactions to attain the optimum conditions revealing that extractant type, extractant volume and pH are the most influential factors. Optimization of the extraction procedures was performed with the aid of Design Expert 8® software, which suggested 58 different experiments. The optimal conditions were 30 µL of 1-octanol as extractant, 100 µL of acetonitrile as a disperser at pH 8. Under the optimized conditions, the method showed linearity over the range of 1–100 ng/mL with a limit of detection of 0.4 ng/mL. The accuracy, the intra- and inter-day precision were assessed, the %recoveries were found to be between 98.48 and 100.81% with %RSD lower than 1.3. Using chemometrics in method optimization helped achieve the maximum possible enrichment with the least effort, time, and reagents while considering all possible interactions between variables.

Quantification of carbohydrates in human serum using gas chromatography–mass spectrometry with the stable isotope-labeled internal standard method

Comparison of two derivatization approaches (silylation and acylation) for carbohydrate separation based on optimizing reaction conditions by artificial neural networks.