Solid-state NMR on thermal and fire residues of bisphenol A polycarbonate/silicone acrylate rubber/bisphenol A Bis(diphenyl-phosphate) (PC/SiR/BDP) and PC/SiR/BDP/zinc borate (PC/SiR/BDP/ZnB) — Part II: The influence of SiR

Solid residues of bisphenol A polycarbonate (containing 0.45 wt% poly(tetrafluoroethylene))/silicone acrylate rubber/bisphenol A bis(diphenyl-phosphate) (PC/SiR/BDP) and PC/SiR/BDP/zinc borate (PC/SiR/BDP/ZnB) after thermal treatment were investigated by solid-state and liquid-state NMR, focusing on the role and interaction of SiR with the other components of the polymer blend.In PC/SiR/BDP, part of the SiR reacts to an amorphous silicate network rather than being completely released in the gas phase. The silicate network consists of Q₄ and Q₃ groups formed via intermediate D and T groups. The D groups are formed by a reaction of SiR with bisphenol-A units as well as phenyl groups of PC and BDP. In addition a small amount of silicon diphosphate was observed after thermal treatment at temperatures higher than 810 K. The same decomposition products (without SiP₂O₇) occur in the solid residues of PC/SiR/BDP/ZnB samples. The formation of intermediate D and T groups occurs earlier, at slightly lower temperatures. Any formation of a borosilicate network was excluded.The results also apply for the fire residues of PC/SiR/BDP and PC/SiR/BDP/ZnB and are thus valuable for understanding the impact of SiR on pyrolysis and flame retardancy mechanisms in the condensed phase during the burning of PC/SiR/BDP blends. SiR was found to influence the pyrolysis and the char formed. Beyond the replacement of highly combustible mechanical modifiers, SiR harbours the potential to enhance flame retardancy.     

Finite group actions on AF algebras obtained by folding the interval

For any finite groupG we construct examples of an AF algebraA and an action byG onA such that the fixed point algebra is not AF. The construction ofA is done by successive foldings and cuttings of the interval in a way originally suggested by Blackadar and, in a different context, by Connes in his talk in Oslo in 1978.     

Synthetic polymers adsorbing bisphenol A and its analogues prepared by covalent molecular imprinting using bisphenol A dimethacrylate as a template molecule

Synthetic polymers which can adsorb bisphenol A (BPA) and related compounds were prepared by a covalent molecular imprinting technique. BPA dimethacrylate, used as template molecule, was polymerized with a crosslinker, triethylene glycol dimethacrylate (TEGDMA) or trimethylol propane trimethacrylate (TRIM). After the polymerization treatment with dilute NaOH was used to cleave BPA from the polymers. For high recovery of BPA with low polymer matrix degradation, the hydrolysis conditions were determined to be treatment with 1.0 mol L^–1 NaOH for 48 h. The binding sites generated by the hydrolysis were evaluated by determination of the retentivity of BPA, BPA analogues, and other endocrine disruptors. The polymers strongly adsorbed compounds with two hydroxyl groups at the 4,4-positions. Generally the TEGDMA-based polymers had stronger affinity than the TRIM-based polymers, although the TRIM-based polymer adsorbed steroidal hormones with two hydroxyl groups, for example 17-estradiol and 17-estradiol, more strongly than the TEGDMA-based polymer, meaning that the crosslinkers affected the properties of the binding sites and, depending upon the target molecules, suitable crosslinkers should be chosen in this system.     

Measurement of bisphenol A in human serum by gas chromatography/mass spectrometry

The purpose of this study is to establish an easy and accurate method for the determination of bisphenol A (BPA) in the human serum. The samples were applied to the C₁₈ solid phase extraction (SPE) column for clean up of samples. The BPA is conjugated with tetrabutylammonium hydrogen sulfate as the counter ion in alkali solution. The ion paired BPA is moves from the aqueous phase to the organic phase as an ion paired extraction. BPA extracted from human serum were derivatized with pentafluorobenzyl bromide (PFBBr). The derivative was analyzed by gas chromatography (GC)/mass spectrometry (MS) using negative chemical ionization (NCI). The instrumental detection limit of BPA was 5 pg/ml (10 fg). The instrumental response between 0.01 and 100 pg/ml of BPA standards was linear (r²=0.998). The recovery of BPA spiked into human serum was 101.0±4.63 (1 pg/ml) and 100.9±3.75 (10 pg/ml), respectively. The concentration of BPA in the human serum from 20 individuals was 0.54 pg/ml.     

Off-Line Concentration of Bisphenol A and Three Alkylphenols by SPE then On-Line Concentration and Rapid Separation by Reverse-Migration Micellar Electrokinetic Chromatography

A method for separation of four environmentally important compounds (three alkylphenols and bisphenol A) by cyclodextrin-modified reverse-migration micellar electrokinetic chromatography (CD-RM-MEKC) has been optimized. On-line concentration, stacking using reverse-migrating micelles and a water plug (SRW), was used to improve the limit of detection. Two main factors affecting the efficiency of enhancement by SRW, injection sample length and water-plug length, are discussed in detail. Compared with the normal 2-s injection, more than 121-fold enhancement of peak area and more than 71-fold enhancement of peak height were achieved with 120-s sample injection after 120-s water-plug injection. With this optimized separation method and SRW technology, limits of detection were found to be 0.089, 0.030, 0.0091, and 0.033 mg L^–1 for 4-nonylphenol, 4-tert-octylphenol, bisphenol A, and 4-tert-butylphenol, respectively. Calibration plots (R² 0.9968) and relative standard deviations (RSD, %) of corrected peak areas and migration time were also satisfactory. Combined with off-line concentration by solid-phase extraction (SPE) this method might be used to determine these contaminants at ppb levels in groundwater samples.     

Determination of environmental estrogens in human urine by high performance liquid chromatography after fluorescent derivatization with p-nitrobenzoyl chloride

A high performance liquid chromatographic method (HPLC) for the simultaneous determination of 4-nonylphenol, bisphenol A, 17α-ethinylestradiol and three endogenic estrogens including 17α-estradiol, 17β-estradiol, estriol in urine sample, based on precolumn derivatization with p-nitrobenzoyl chloride, is presented in this paper. The estrogens mentioned above in urine were firstly hydrolyzed with 0.6 mol/l HCl, and then enriched and cleaned-up by ENV-18 C18 solid phase extraction (SPE) column. The estrogens on column were eluted with dichloromethane, and the eluent was evaporated to dryness under gentle nitrogen flow. The residue was allowed to react with p-nitrobenzoyl chloride at 25 °C for 30 min. Separation was performed on a C18 column with gradient elution using acetonitrile and water as mobile phase. A fluorescence detection system was used to detect the fluorescent derivatization products. The detection limit of the method was 2.7 μg/l for bisphenol A and 17β-estradiol, 2.9 μg/l for 4-nonylphenol, 4.6 μg/l for 17α-estradiol and 17α-ethinylestradiol and 8.3 μg/l for estriol, respectively. The relative standard deviations (R.S.D.) ranged from 1.29 to 4.52% and the recoveries ranged from 85.5 to 99.9%. The method was applied to the determination of those six estrogens mentioned above in human urine samples collected from 20 healthy volunteers (aged 21-29). Bisphenol A (BPA) and 4-nonylphenol (NP) were detected with average contents of 1.22 ± 1.38 mg/l and 0.38 ± 0.77 mg/l in 10 male urine samples and 1.29 ± 1.22 mg/l and 0.05 ± 0.05 mg/l in 10 female urine samples, respectively. 17α-ethinylestradiol (α-EE2) was also detected with average contents of 0.13 ± 0.41 mg/l and 0.06 ± 0.15 mg/l in male and female urine samples, respectively.     

Determination of Compounds from Epoxy Resins in Food Simulants by HPLC-Fluorescence

Summary A fluorimetric-detection RP-HPLC method is developed for the separation and quantification of bisphenol A diglycidyl ether (BADGE), bisphenol F diglycidyl ether (BFDGE), its hydrolysis and chlorohydroxy derivatives, and NOGE and BADGE oligomers. This method was applied to test an epoxy resin used as a coating for food contact packaging materials with two different heat treatments in the curing process. Migration of these compounds was evaluated in three food simulants: 3% (w/v) acetic acid, 10% (v/v) ethanol, rectified olive oil and also in acetonitrile. A simple extraction procedure was also applied to obtain olive oil extracts. Quantification was performed by using external calibration, and correlation coefficients were greater than 0,996 and the limit of detection (LOD) was 0.02 mg L^–1 for all substances. HPLC-MS method was applied to confirm derivatives and oligomers identity.Presented at: International Symposium on Separation and Characterization of Natural and Synthetic Macromolecules, Amsterdam, The Netherlands, February 5–7, 2003     

Selective determination of bisphenol A (BPA) in water by a reversible fluorescence sensor using pyrene/dimethyl β-cyclodextrin complex

A bifurcated optical fiber chemical sensor for continuous monitoring of bisphenol A (BPA) has been proposed based on the fluorescence quenching (λ_ex/λ_em = 286/390 nm) of pyrene/dimethyl β-cyclodextrin (HDM-β-CD) supramolecular complex immobilized in a plasticized poly(vinyl chloride) (PVC) membrane, in which pyrene served as a sensitive fluorescence indicator probe. The decrease of the fluorescence intensity of pyrene/HDM-β-CD complex upon the addition of BPA was attributed to the displacement of pyrene by BPA, which has been utilized as the basis of the fabrication of a BPA-sensitive fluorescence sensor. The response mechanism of the sensor was discussed in detail. The sensor exhibited a dynamic detection range from 7.90 × 10⁻⁸ to 1.66 × 10⁻⁵ mol L⁻¹ with a detection limit of 7.00 × 10⁻⁸ mol L⁻¹, and showed excellent reproducibility, reversibility, selectivity, and lifetime. The proposed sensor was successfully used for the determination of BPA in water samples and landfill leachate.     

不完全相反转发展过程的流变行为

以动态应力流变仪ＤＳＲ（ＤｙｎａｍｉｃＳｔｒｅｓＲｈｅｏｍｅｔｅｒ）对双酚Ａ型环氧树脂在低乳化剂浓度（２３３ｗｔ％）下的相反转乳化过程进行了稳态应力扫描及动态频率扫描实验．实验结果表明,体系在相反转点前表现为牛顿流体行为,粘度几乎不变;相反转点时,体系粘度增加幅度很小,体系的有关动态流变参数（剪切储能模量、损耗模量和复数粘度）均出现极小值,将此归于局部连续水相的润滑作用;进一步加水,体系的动态流变量增加,意味着相反转在相反转点后仍在继续进行．所以,体系在低乳化剂浓度时,发生了不完全相反转．     

双酚A型环氧树脂水基化微粒分析

高分子树脂水基化微粒化就是使高分子树脂以微粒形式分散于水中,高分子乳液、悬浮液都属于此范畴．因其不含有机溶剂,且具有无环境污染及不易失火等优点,放这方面的研究正成为高分子技术的一个研究热点．通常的乳液聚合或悬浮聚合方法是从小分子单体到聚合物水基化体系的化学反应过程,一般只适于制备加聚物的水基化体系,而不适用于制备维聚物的水基化体系．本文提出的相反转技术是一种有效的制备高分子水基化体系的方法,它能将几乎所有的高分子树脂通过物理的乳化方法制成相应的水基化体系[1,2],大大拓宽了其制备范围．相反转[3。4]…