Contaminant detection in treated water using Optiqua’s MiniLab™ biosensing system: a case study for Bisphenol A

An inhibition assay for detection of Bisphenol A (BPA) in treated water has been developed and validated for the MiniLab? system from Optiqua Technologies. This biosensor-based analytical system can be used for detection of specific contaminants in solution. The system uses an integrated optic Mach-Zehnder interferometer chip that is functionalised with a biochemical interface layer. The sensor chip surface was first coated with aminodextran which formed a hydrophilic layer suitable for further modification. 4,4-bis(4-hydroxyphenyl) valeric acid (BVA), which is a structural analogue of BPA, was then successfully coupled to the aminodextran layer. This surface chemistry was used in a qualitative inhibition assay format for the selective detection of the presence of BPA. The assay was developed and optimised using a polyclonal anti-BPA antibody. Samples from 12 different water matrices of Singapore were spiked with known amounts of BPA and tested with the MiniLab? system. The working range of the BPA inhibition assay is from 0.5 to 5 µg/L. Intra- and inter-assay variations were measured, with calculated relative standard deviation averaging of about 15%. BPA concentrations of the spiked samples were also verified and confirmed with LC-MS. Such functionalised biosensor chip can be reused for more than 200 sample injections over a period longer than 6 months. Developed as a robust, user-friendly and cost-effective system that can be field deployed, the MiniLab? system enables target-specific assays currently only available in the lab to become available in the field.     

On the capacity of the multiple-hop relay channel with linear relaying

The relay nodes with linear relaying transmit linear combination of their past received signals. The capacity of the multiple-hop Gaussian relay channel with linear relaying is derived, assuming that each node in the channel only communicates with its nearest neighbor nodes. The capacity is formulated as an optimization problem over the relaying matrices and the covariance matrix of the signals transmitted from the source. It is proved that the solution to this optimization problem is equivalent to a “single-letter” optimization problem when some certain conditions are satisfied. We also show that the solution to the “single-letter” optimization problem has the same form as the expression of the rate achieved by time-sharing amplify-and-forward (TSAF). In order to solve this equivalent problem, we give an iterative algorithm. Simulation results show that the achievable rate with TSAF is close to the capacity, if channel gain of one certain hop is smaller than that of all the other hops relatively.     

The impact of alkaline earth oxides on Bi2O3 and their catalytic activities in photodegradation of Bisphenol A

The BPA into wastewater has posed a threat to environment and human health. Hence, we aimed to eliminate BPA in a short time and with a rapid degradation rate from food wastewater. Herein, the effects of different alkaline-earth oxide doped with Bi₂O₃ nanoparticles on the photocatalytic degradation of bisphenol A were investigated. SrO-Bi₂O₃, CaO-Bi₂O₃, and MgO-Bi₂O₃ binary oxides were prepared by wet-impregnation method. The structural and optical features of catalysts were clarified BET, XRD, DRS, FT-IR, PL, and SEM techniques. The photocatalytic activities of catalysts were compared for different light sources. Considering that the characterization analysis and experimental results, the highly improved photocatalytic activity was mainly attributed to the effective structure of the SrO-Bi₂O₃ binary oxide and the strong alkali properties in the nanocomposite. Obviously, 5wt% SrO-Bi₂O₃ photocatalyst showed more excellent degradation performance and highest degradation reaction rate (0.21 mg l^–1 min^–1) within 30 min. It was observed that the photocatalytic activity improved by the additive of alkaline oxide on Bi₂O₃.     

Quantitation of free and total bisphenol A in human urine using liquid chromatography-tandem mass spectrometry

Bisphenol A (BPA) is employed in the synthesis of polycarbonate plastics and epoxy resins and is widely used in consumer products including as a coating for the inside of almost all food and beverage containers and thermal-imaging paper. Bisphenol A is considered to have important health implications because it possesses weak estrogenic activity and can leach from storage containers resulting in its consumption by both humans and animals. It is metabolized in the body and excreted into urine as a glucuronide derivative. In this report, we present an accurate, selective, sensitive, and reproducible high-performance liquid chromatography/tandem mass spectrometry (HPLC/MS/MS) method for the quantitation of BPA in human urine, which is not prone to exogenous contamination. BPA-glucuronide is hydrolyzed enzymatically, extracted with toluene, derivatized with dansyl chloride, and the BPA-(dansyl)(2) derivative is analyzed using reversed-phase HPLC/MS/MS. Calibration was linear to 50 ng/mL with a limit of quantitation of 50 pg/mL and a limit of detection of 5 pg/mL.     

分子印迹基质固相分散-超高效液相色谱法测定儿童玩具中双酚A

以双酚A为模板分子,4-乙烯基吡啶为功能单体合成了双酚A分子印迹聚合物(BPAMIP),作为基质固相分散吸附剂,用于提取儿童玩具中双酚A。样品溶液均匀地分散在BPA-MIP中,风干后用二氯甲烷淋洗,然后用甲醇(35+65)溶液作洗脱剂将双酚A洗下,收集洗出液供高效液相色谱测定。结果表明:聚合物对印迹分子具有很好的亲和性和特异选择性。方法的线性范围为1.5～100.0mg·L~(-1),检出限(3S/N)为0.12mg·L~(-1)。在5个浓度水平下做加标回收试验,回收率在94.9%～99.1%之间,相对标准偏差(n=6)在1.2%～3.4%之间。     

Electrospinning fabrication of partially crystalline bisphenol A polycarbonate nanofibers: Effects on conformation, crystallinity, and mechanical properties

The application of an electrostatic and centrifugal field (1800 rpm) in a novel electrospinning process was shown to improve the degree of uniaxial alignment in polymer nanofibers and to enhance orientational order in polymer chains, producing bisphenol A polycarbonate (BPAPC) nanofibers with superior mechanical properties. High-speed videography showed that the additional centrifugal field effectively removed electrical bending instability and promoted molecular orientation during the electrospinning process. Infrared spectroscopic (IR) characterization revealed that the fraction of trans–trans conformers in BPAPC nanofibers reached 67% under optimal electrospinning conditions (25 kV and 1800 rpm at 25 °C). Modulated differential scanning calorimetry (MDSC) and wide-angle X-ray diffraction (WXRD) assays showed that a degree of crystallinity of 6.5% could be achieved. Moreover, two crystal phases at angles of 2θ = 17.3° and 21.9° were produced in BPAPC nanofibers. The elastic modulus of BPAPC nanofibers with a crystallinity of 6.5% was 7.11 and 5.13 GPa, as measured via atomic force microscopy (AFM) and nanoindenter (NI) experiments, respectively. These results demonstrated that the mechanical behavior of BPAPC nanofibers could be improved by conducting the proposed electrospinning technique. Moreover, BPAPC nanofibers produced through the proposed method could be potentially applied for the reinforcement of composites.     

Outdoor and accelerated weathering studies of bisphenol A polycarbonate

The influence of outdoor weathering on the degradation rate of unstabilized bisphenol A polycarbonate (BPA-PC) films is investigated and compared to the results found for indoor accelerated weathering conditions, using UV and IR spectroscopy. At the same dosage, changes in UV and IR were larger for the accelerated than for the outdoor weathered samples, this could be explained by the lower degradation temperature during outdoor exposures. The difference between outdoor and accelerated weathering is according to the IR measurement larger than according to the UV measurement. This difference is ascribed to difference in wavelength distribution between the spectra of the light emitted in the accelerated test and from the terrestrial sunlight. The larger difference for the IR results than for the UV results suggests a difference in ratio between photo-Fries rearrangements and photo-oxidation reaction between both exposures.     

分子印迹固相萃取检测罐装食品中双酚A

以双酚A为模板分子,3-氨基丙基乙氧基硅烷为功能单体,通过溶胶-凝胶反应合成双酚A分子印迹纳米硅胶微球。以印迹微球为固相萃取吸附剂,优化固相萃取条件,确定二氯甲烷为上样溶剂。固相萃取选择性实验表明,在双酚A及其结构类似物四溴双酚A、双酚C、壬基酚的混合物溶液中,印迹萃取柱对双酚A具有良好的选择性能,回收率达到90.7%。浓度为2.5和5μmol/L的加标罐装食品样品,经印迹萃取柱预处理,液相色谱检测得到回收率72%～84%,相对标准偏差2.9%～4.4%。     

Competitive CE-UV binding tests for selective recognition of bisphenol A by molecularly imprinted polymer particles

Capillary electrophoresis with ultraviolet detection (CE-UV) was used to perform competitive binding tests to demonstrate the selective recognition of bisphenol A (BPA) by molecularly imprinted polymer (MIP) particles. Cross-linking polymerization of methacrylic acid (MAA) and ethylene glycol dimethacrylate (EGDMA) in the presence of BPA yielded MIP particles with an average diameter of 164 ± 15 nm. Their ability to recognize BPA in the presence of nonionic, anionic, and cationic water contaminants was investigated. Binding efficiency was rapidly determined, after sequential injection of particles first and compounds next into the fused-silica capillary provided a short overlapping time during their electrophoretic migrations. The MIP particles exhibited high-binding efficiency (99 ± 1%) for BPA. Neither diclofenac nor metformin affected BPA binding, and 2-hydroxy-4-methoxybenzophenone was even displaced from the particles by BPA. These results verified the high selectivity of MIP toward its target compound.     

Novel Extraction for Endocrine Disruptors in Atmospheric Particulate Matter

A rapid and efficient sample preparation method, which is called microwave-assisted microsolid phase extraction, was developed for the determination of endocrine disrupting chemicals in atmospheric particulate matter. The endocrine disrupting chemicals included bisphenol A, diethyl phthalate, dibutyl phthalate, and di(2-ethylhexyl) phthalate. The endocrine disrupting chemicals were isolated by microwave-assisted extraction following adsorption by copper(II) isonicotinate using microsolid phase extraction. The endocrine disrupting chemicals were subsequently determined by high performance liquid chromatography with an ultraviolet detector. The extraction was optimized for temperature, time, desorption time, and desorption solvent. Limits of detection (in the range of 2.0–8.5 nanograms per liter), limits of quantification (in the range of 6.6–28.0 nanograms per liter), and repeatability of the procedure (less than 10 percent) were established. Diethyl phthalate, diethyl phthalate, and di(2-ethylhexyl) phthalate were determined at values from 0.57 to 68.8 nanograms per cubic meter in atmospheric particulate matter collected from an urban area, a business center, and an industrial site in Dongguan, China. The concentration of bisphenol A was below the detection limit in these samples.