In-vitro oxidation of bisphenol A: Is bisphenol A catechol a suitable biomarker for human exposure to bisphenol A?

The extensive use of bisphenol A (BPA) in the manufacture of consumer products results in widespread human exposure to the chemical. In the body, BPA undergoes first-pass metabolism to form BPA glucuronide, considered to be a major BPA byproduct. Concentrations of total (free plus conjugated) urinary species of BPA are used to assess human exposure to BPA. However, because BPA can be present in numerous consumer and household products, potential contamination with parent BPA during collection and handling may pose a challenge when measuring BPA in such biological samples as blood or urine. In this study we investigated the in-vitro phase I metabolism of BPA in rat and human liver microsomes by using on-line solid-phase extraction–high-performance liquid chromatography–tandem mass spectrometry to identify phase I metabolites (e.g., BPA oxidation products) that could be used as potential alternative biomarkers of BPA exposure. We unambiguously identified 5-hydroxy BPA (BPA catechol) as an in-vitro oxidative metabolite of BPA, but human microsomes oxidized only about 10% of BPA to BPA catechol. We evaluated the usefulness of BPA catechol as a potential biomarker of human exposure to BPA by measuring total concentrations of BPA catechol and BPA in 20 urine samples. We detected BPA catechol at much lower concentrations and frequency than those of BPA. Furthermore, we found that free BPA catechol was rather unstable in urine, which highlights the importance of sampling techniques to adequate interpretation of biomonitoring data. Together, these findings suggest that BPA catechol may not be a suitable biomarker of environmental exposure to BPA, but could be used to confirm BPA exposure in special populations or in situations when urine specimens were potentially contaminated with BPA.     

Measurement of bisphenol A, bisphenol A ß-D-glucuronide, genistein, and genistein 4'-ß-D-glucuronide via SPE and HPLC-MS/MS

Bisphenol A (BPA) is a synthetic industrial reactant used in the production of polycarbonate plastics, and genistein is a natural phytoestrogen abundant in the soybean. Current studies investigating the endocrine-disrupting effects of concomitant exposures to BPA and genistein have warranted the development of an analytical method for the simultaneous measurement of BPA and genistein, as well as their primary metabolites, bisphenol A ?-d-glucuronide (BPA gluc) and genistein 4′-?-d-glucuronide (genistein gluc), respectively. All four analytes were extracted from rat plasma via solid phase extraction (SPE). Three SPE cartridges and four elution schemes were tested. Plasma extraction using Bond Elut Plexa cartridges with sequential addition of ethyl acetate, methanol, and acetonitrile yielded optimal average recoveries of 98.1 ± 1.8% BPA, 94.9 ± 8.0% genistein, 91.4 ± 6.1% BPA gluc, and 103 ± 6.1% genistein gluc. Identification and quantification of the four analytes were performed by a validated HPLC-MS/MS method using electrospray ionization and selective reaction monitoring. This novel analytical method should be applicable to the measurement of BPA, genistein, BPA gluc, and genistein gluc in urine, cultures, and tissue following in vivo exposures. While reports of the determination of BPA and genistein independently exist, the simultaneous optimized extraction and detection of BPA, genistein, BPA gluc, and genistein gluc have not previously been reported.     

CuS–MWCNT based electrochemical sensor for sensitive detection of bisphenol A

The rapid and simple detection of bisphenol A is very important for the safety and reproduction of organisms. Here, a sensitive and reliable electrochemical sensor was established for bisphenol A detection based on the high amplification effect of copper sulfide-multi-walled carbon nanotube (CuS–MWCNT) nanocomposites. The flower-like CuS–MWCNT were successfully synthesized by a simple hydrothermal method accompanied by polyvinylpyrrolidone (PVP). Compared with bare glassy carbon electrode (GCE), CuS–MWCNT modified GCE could amplify the electrochemical signals in about ten times, which was attributed to the synergistic effect of CuS and MWCNT. The MWCNT could increase the specific surface area of electrodes and improve the electrode activity. The integration of CuS could further enhance the electrode conductivity as well as accelerate the electron transfer rate. Raman spectra and transmission electron microscope (TEM) were used to characterize the successful fabrication of CuS–MWCNT nanocomposites and its uniform and monodispersed morphology. Under optimizing conditions, the oxidation currents of bisphenol A via the differential pulse voltammetric (DPV) showed a good linear relationship with its concentration in a wide range of 0.5–100 μM, with a detection limit of 50 nM. This electrochemical sensor of bisphenol A provided a convenient and economical platform with high sensitivity and reproducibility, which had great potential in environmental monitoring.     

Is the bisphenol A biradical formed in the pyrolysis of polycarbonate?

An unknown species has been detected in the analysis of the products in a pyrolysis of polycarbonate using Li(+) ion-attachment mass spectrometry (IAMS). The mass spectra exhibited a Li(+) adduct peak at m/z 233 that was tentatively assigned to bisphenol A (BPA) biradical. Experimentally, this assignment was supported by the observation that the production rate increased under an inert nitrogen atmosphere. To further confirm the assignment, the stability of the BPA biradical to intramolecular rearrangement reactions as well as unimolecular decomposition has been analyzed via density functional theory calculations [B3LYP/6-311+G(3df,2p)]. The results show that the bisphenol A biradical is an open-shell biradical singlet that is stable to unimolecular decomposition. Although some of the proposed intramolecular rearrangement products have lower energies than those of the BPA diradical, these pathways have large reaction barriers and the kinetic lifetime of the radical is expected to be of the order of hours under the conditions of the experiment. The calculations also reveal that the bisphenol A diradical has large Li(+) affinities supporting the fact that these Li(+) complexes could be detected in the Li(+) ion attachment mass spectrometry. On the basis of these results the Li(+) adduct peak at m/z 233 detected in the pyrolysis of polycarbonate is assigned to the bisphenol A biradical.     

Depolymerization of Poly（bisphenol A carbonate） in Subcritical and Supercritical Toluene

The depolymerization of poly(bisphenol A carbonate)(PC) in subcritical and supercritical toluene was studied. The experimental parameters, which influence the depolymerization reaction such as temperature (570-633 K), pressure (4.0-7.0 MPa), reaction time (5-60 min), and toluene to PC weight ratio (3.0-11.0), were investigated, and the reaction products were determined by GC, GC/MS and FT-IR spectrometer. It was found that the main product of the depolymerization reaction was bisphenol A(BPA). BPA accounted for over 55.7% of the depolymerization products at reaction temperature 613 K, pressure 5.0-6.0 MPa, reaction time 15 min and toluene/PC weight ratio of around 7.0.     

Determination of bisphenol A and bisphenol B in canned seafood combining QuEChERS extraction with dispersive liquid–liquid microextraction followed by gas chromatography–mass spectrometry

A new simple and reliable method combining an acetonitrile partitioning extractive procedure followed by dispersive solid-phase cleanup (QuEChERS) with dispersive liquid–liquid microextraction (DLLME) and further gas chromatography mass spectrometry analysis was developed for the simultaneous determination of bisphenol A (BPA) and bisphenol B (BPB) in canned seafood samples. Besides the great enrichment factor provided, the final DLLME extractive step was designed in order to allow the simultaneous acetylation of the compounds required for their gas chromatographic analysis. Tetrachloroethylene was used as extractive solvent, while the acetonitrile extract obtained from QuEChERS was used as dispersive solvent, and anhydride acetic as derivatizing reagent. The main factors influencing QuEChERS and DLLME efficiency including nature of QuEChERS dispersive-SPE sorbents, amount of DLLME extractive and dispersive solvents and nature and amount of derivatizing reagent were evaluated. DLLME procedure provides an effective enrichment of the extract, allowing the required sensitivity even using a single quadropole MS as detector. The optimized method showed to be accurate (>68?% recovery), reproducible (<21?% relative standard deviation) and sensitive for the target analytes (method detection limits of 0.2?μg/kg for BPA and 0.4?μg/kg for BPB). The screening of several canned seafood samples commercialized in Portugal (total?=?47) revealed the presence of BPA in more than 83?% of the samples with levels ranging from 1.0 to 99.9?μg/kg, while BPB was found in only one sample at a level of 21.8?μg/kg.     

UHPLC–MS/MS method for the determination of bisphenol A and its chlorinated derivatives,bisphenol S,parabens, and benzophenones in human urine samples

In the present work, a new method based on a sample treatment by dispersive liquid–liquid microextraction (DLLME) for the extraction of six bisphenols (bisphenol A, bisphenol S, and monochloro-, dichloro-, trichloro-, and tetrachlorobisphenol A), four parabens (methyl-, ethyl-, propyl-, and butylparaben), and six benzophenones (benzophenone-1, benzophenone-2, benzophenone-3, benzophenone-6, benzophenone-8, and 4-hydroxybenzophenone) in human urine samples, followed by ultrahigh-performance liquid chromatography–tandem mass spectrometry (UHPLC–MS/MS) analysis, is validated. An enzymatic treatment allows determining the total content of the target EDCs. The extraction parameters were accurately optimized using multivariate optimization strategies. Ethylparaben ring-¹³C₆, benzophenone-d₁₀, and bisphenol A-d₁₆ were used as surrogates. Limits of quantification ranging from 0.1 to 0.6 ng mL^?1 and interday variabilities (evaluated as relative standard deviations) from 2.0 to 13.8 % were obtained. The method was validated using matrix-matched standard calibration followed by a recovery assay with spiked samples. Recovery rates ranged from 94 to 106 %. A good linearity, for concentrations up to 300 ng mL^?1 for parabens and 40 ng mL^?1 for benzophenones and bisphenols, was also obtained. The method was satisfactorily applied for the determination of target compounds in human urine samples from 20 randomly selected individuals.     

The Interaction of Arsenazo III with Nd(III)—A Chemometric and Metrological Analysis

Interactions of Arsenazo III with Nd(III) in aqueous solutions (pH range 3 to 4) were studied using a spectrophotometric method. Some discrepancies are present in literature concerning the concentrations of the prevailing species and their composition. Threshold bootstrap computer-assisted target factor analysis (TB CAT) was applied to the evaluation of UV-VIS spectra of Arsenazo III in aqueous solutions containing varying amounts of neodymium(III) ions. The thus obtained experimental data are interpreted with consideration of the measurement uncertainties affecting this system. Within the limits of resolution of the experimental method, two complexes NdAazo and Nd(Aazo)₂ were indicated in the studied pH range. The values of formation constants for log ₁₀ β ₁₁ fall in the range 4.9 to 6.3 and for log ₁₀ β ₁₂ fall between 10.5 and 12.1.     

Surface-imprinted core–shell Au nanoparticles for selective detection of bisphenol A based on surface-enhanced Raman scattering

Surface-imprinted core–shell Au nanoparticles (AuNPs) were explored for the highly selective detection of bisphenol A (BPA) by surface-enhanced Raman scattering (SERS). A triethoxysilane-template complex (BPA-Si) was synthesized and then utilized to fabricate a molecularly imprinted polymer (MIP) layer on the AuNPs via a sol–gel process. The imprinted BPA molecules were removed by a simple thermal treatment to generated the imprint-removed material, MIP-ir-AuNPs, with the desired recognition sites that could selectively rebind the BPA molecules. The morphological and polymeric characteristics of MIP-ir-AuNPs were investigated by transmission electron microscopy and Fourier-transform infrared spectroscopy. The results demonstrated that the MIP-ir-AuNPs were fabricated with a 2 nm MIP shell layer within which abundant amine groups were generated. The rebinding kinetics study showed that the MIP-ir-AuNPs could reach the equilibrium adsorption for BPA within 10 min owning to the advantage of ultrathin core–shell nanostructure. Moreover, a linear relationship between SERS intensity and the concentration of BPA on the MIP-ir-AuNPs was observed in the range of 0.5–22.8 mg L⁻¹, with a detection limit of 0.12 mg L⁻¹ (blank ± 3 × s.d.). When applied to SERS detection, the developed surface-imprinted core–shell MIP-ir-AuNPs could recognize BPA and prevent interference from the structural analogues such as hexafluorobisphenol A (BPAF) and diethylstilbestrol (DES). These results revealed that the proposed method displayed significant potential utility in rapid and selective detection of BPA in real samples.     

A paper-based competitive lateral flow immunoassay for multi β-agonist residues by using a single monoclonal antibody labelled with red fluorescent nanoparticles

An ultrasensitive paper based lateral flow assay is described for rapid and simultaneous fluorometric detection of several β-agonists including clenbuterol and its chemical analogues (mabuterol, brombuterol, cimaterol, cimbuterol, bromchlorbuterol and banbuterol). A nonspecific monoclonal antibody (mAb) against clenbuterol and its analogues was prepared and employed in a competitive immunoassay where mAb conjugated to fluorescent nanoparticles and free β-agonists compete for the binding sites. This enables rapid screening for the 7 β-agonists in a single run that takes about 8 min. Detection limits for the seven β-agonists are <50 pg g^?1 of pork. Recoveries ranged from 69.5% to 102.4%, and relative standard deviations were ±15%. The assay was applied to the analysis of both using spiked and unspiked pork for β-agonists, and the results compare well to those obtained by HPLC-MS.

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Graphical abstract Schematic presentation of an ultra sensitive fluorescent nanoparticle based paper based assay for rapid detection of multi β-agonists in pork tissue.

     

Electrochemical detection of bisphenol A based on Co nanoparticles/N-doped carbon nanotubes compositesEI北大核心CSCD

Co nanoparticles and nitrogen-doped carbon nanotubes （NCNTs）were prepared by calcination of metal-organic material ZIF-67 in a reductive atmosphere of H2 and Ar gas,and modified on the surface of glassy carbon electrod（GCE）for the detection of bisphenol A（BPA）. The Co/NCNTs composites exhibited superior electrocatalytic performance for BPA oxidation owing to the synergistic effect between chemical composition and the specific structure of the Co/NCNTs composites. In optimal conditions,Co/NCNTs/GCE exhibited a linear range of 0.01-20 μµmol/L for BPA（R2=0.998）. The prepared electrode was employed to detect the content of BPA in real samples with the recoveries of 98.4%-104.6%. © 2023, Youke Publishing Co.,Ltd. All rights reserved.     

A Structural and Calorimetric Study on the Interaction Between Jack Bean Urease and Cyanide Ion

The cyanide ion was studied as an effecter of Jack bean urease at 300 K in 30 mmol⋅L⁻¹ Tris buffer, pH=7. The inhibition was investigated by isothermal titration calorimetry (ITC). The extended solvation model was used for CN⁻+JBU interaction over the whole range of CN⁻ concentrations. The binding parameters recovered from the solvation model were attributed to the interaction with cyanide ion. It was found that cyanide ion acted as a noncooperative inhibitor of urease, and there is a set of 12 identical and independent binding sites for CN⁻ ions. The dissociation equilibrium constant is 749.99 μmol⋅L⁻¹. The molar enthalpy of binding is ΔH=−13.60 kJ⋅mol⁻¹.     

Volumetric Properties of Aqueous Solutions of L-Glutamic Acid and Magnesium-L-Glutamate

Densities of aqueous solutions of L-glutamic acid and magnesium-L-glutamate were determined from T=288.15 to 333.15 K at 5 K temperature intervals. The measured densities were used to evaluate the apparent molar volumes, V _2,φ (m,T), the cubic expansion coefficients, α(m,T), and the changes of isobaric heat capacities with respect to pressure, (∂ C _p /∂ p) _T,m . They were qualitatively correlated with changes in the structure of water that occur when L-glutamic acid or magnesium-L-glutamate are present.     

Intramolecular Charge Transfer Reaction in Solutions of Low to High Electrolyte Concentrations: Interplay between Friction and Solvation

Fluorescence emission spectroscopy have been used to investigate the effects of electrolytes on the excited state intramolecular charge transfer (ICT) reaction in 4-(1-azetidinyl)benzonitrile (P4C) in very dilute to concentrated electrolyte solutions of ethyl acetate (EA), acetonitrile (AN) and ethanol (EtOH). In the limit of very low electrolyte concentrations, the reaction rate (=1/τ _rxn, τ _rxn being the reaction time) is found to decrease with increasing electrolyte concentration, the extent of decrease being the maximum in EA and the minimum in AN. At moderate to higher electrolyte concentrations, however, the rate increases upon further addition of electrolyte. The observed non-monotonic electrolyte concentration dependence of rate is believed to occur due to a novel interplay between friction and solvation experienced by the photo-excited reactant in solution. Moreover, the long time decay constant and amplitude of the bi-exponential decay of the time resolved fluorescence emission intensity also show a significant electrolyte concentration dependence which corroborates the relevant steady-state results. Electronic Supplementary Material  The online version of this article () contains supplementary material, which is available to authorized users.     

Molecularly imprinted adsorbents for preconcentration and isolation of progesterone and testosterone by solid phase extraction combined with HPLC

The use of a novel procedure of solid-phase extraction with molecularly imprinted polymers (MISPE) has been described. A MISPE procedure relying on tailor-made, artificial-mimic materials capable of selectively rebinding target analytes (steroids) based on a combination of recognition mechanisms, such as size, shape and functionality, was custom designed for progesterone and testosterone. The combination of MISPE with LC/DAD is a simple and an efficient method for the determination and quality control of progesterone and testosterone in human urine samples.     

Influence of Europium speciation on its accumulation in Brassica napus and over-expressing BnTR1 lines

This study aimed at influence of europium speciation on its accumulation in Brassica napus (CK) and over-expressing BnTR1 lines (OE), and the kinetics of Eu uptake were investigated. These results indicated that the uptake in the roots of OE was higher than that of CK at high concentrations of europium and even the enrichment in the roots of OE was as high as 20,000 mg/kg at 328.9 μΜ Eu, this suggested that OE might have better resistance to uranium than CK. The time kinetics in plants showed that there had the similar trend between CK and OE. The formation of Eu³⁺at pH 5 in deionized water was beneficial to plants enrichment Eu and carbonate could reduce the adsorption of Eu in two group and phosphate almost completely impress the adsorption of Eu in two group, but citric acid could enhance europium root-to-shoot translocation in two group. These results would help understanding the mechanism of Eu uptake in Brassica napus (CK) and over-expressing BnTR1 lines (OE), therefore properly developing efficient europium/americium phytoremediation.     

Removal of bisphenol A via a hybrid process combining oxidation on β-MnO2 nanowires with microfiltration

A novel hybrid process combining β-MnO₂ nanowires oxidation and microfiltration was adopted to remove bisphenol A (BPA), an endocrine disrupting chemical (EDC) in the aquatic environment. The β-MnO₂ nanowires synthesized via a facile hydrothermal method were characterized by X-ray diffraction, transmission electron microscopy, field-emission scanning electron microscope, and nitrogen sorption. It was demonstrated that β-MnO₂ nanowires can degrade BPA effectively. Investigation on operation parameters indicated that oxidation of BPA using β-MnO₂ nanowires was evidently dependent on pH, while humic acid and coexisting metal ions such as Ca²⁺, Mg²⁺, and Mn²⁺ induced suppressive effects. After oxidation, a crossflow microfiltration process was conducted to efficiently separate and recover the β-MnO₂ nanowires from treated water. Membrane fouling study showed that the as-synthesized β-MnO₂ nanowires possess excellent mechanical stability and was able to retain the 1D structure with high aspect ratios after reaction, thus significantly reducing membrane pore blocking in the microfiltration process.     

A capillary column packed with a zirconium(IV)-based organic framework for enrichment of endogenous phosphopeptides

A zirconium(IV)-based metal organic framework (Zr-MOF) was deposited on polydopamine-coated silica microspheres to form microspheres of type SiO₂@PDA@Zr-MOF. These were packed into capillary columns for enrichment of phosphopeptides. The column was off-line coupled to both matrix-assisted laser desorption/ionization time of flight mass spectrometry and LC-ESI-MS/MS. The method has a detection limit as low as 4 fmol of β-casein digest and a selectivity as high as 1:1000 (molar ratio of β-casein and BSA digest). It was applied to the analysis of human saliva. In total, 240 endogenous phosphopeptides were identified in only 25 μL human saliva.

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Graphical abstract A zirconium-based metal organic framework (Zr-MOF) was modified outside of polydopamine-coated silica microspheres to form microspheres named SiO₂@PDA@Zr-MOF. Then they were packed in capillary columns for selective enrichment of phosphopeptides via interaction between Zr-O clusters and phosphate groups. The pre-concentration resulted in a better detection of phosphopeptides by mass spectrometry. Tris: Tris(hydroxymethyl)aminomethane; DMF: Dimethyl Formamide; Zr-MOF: Zirconium(IV)-organic framework; MOAC: Metal oxide affinity chromatography.

     

A DFT Study on the Interactions between Sulfolane and Aromatic Hydrocarbons

The B3LYP method with 6-31G^*, 6-311+G^* and aug-cc-pvdz basis sets was used to predict the geometries of aromatic hydrocarbon (benzene, toluene, benzonitrile) and sulfolane interaction systems. Nine stable conformers were obtained with no imaginary frequencies. The interaction energies of these binary mixtures have been obtained at the B3LYP/6-31G^*, B3LYP/6-311+G^* and B3LYP/aug-cc-pvdz levels. The natural bond orbital (NBO) and the atoms in molecules theory (AIM) were used to analyze the nature of the interactions at these levels. The results show that hydrogen bonds are present in these systems. Of all levels, the interaction of the sulfolane-benzonitrile system at B3LYP/6-311+G^* is the strongest with an interaction energy of −21.84 kJ⋅mol⁻¹ (BSSE corrected), and the intensity order of the interactions is A(2) > A(3) > A(1), B(2) > B(3) > B(1), C(2) > C(3) > C(1), and C(2) > B(2) > A(2).