Simultaneous determination of UV filters and polycyclic musks in aqueous samples by solid-phase microextraction and gas chromatography–mass spectrometry

A simple, precise and accurate method for the simultaneous determination of four UV filters and five polycyclic musks (PCMs) in aqueous samples was developed by solid-phase microextraction coupled with gas chromatography–mass spectrometry (SPME-GC–MS). The operating conditions affecting the performance of SPME-GC–MS, including fiber thickness, desorption time, pH, salinity, extraction time and temperature have been carefully studied. Under optimum conditions (30 μm PDMS fiber, 7 min desorption time, pH 7, 10% NaCl, 90 min extraction time at 24 °C), the correlation coefficients (r²) of the calibration curves of target compounds ranged from 0.9993 to 0.9999. The limit of detection (LOD) and limit of quantification (LOQ) ranged from 0.2 to 9.6 ng L⁻¹ and 0.7 to 32.0 ng L⁻¹, respectively. The developed procedure was applied to the determinations of four UV filters and five PCMs in river water samples and internal standard was used for calibration to compensate the matrix effect. Good relative recoveries were obtained for spiked river water at low, medium and high levels. The proposed SPME method was compared with traditional SPE procedure and the results found in river water using both methods were in the same order of magnitude and both are quite agreeable.     

On-line renewable solid-phase extraction hyphenated to liquid chromatography for the determination of UV filters using bead injection and multisyringe-lab-on-valve approach

For the first time, an automatic sample pre-treatment/detection method is proposed for the multiclass determination of UV filters (namely, benzophenone-3, ethylhexylmetoxycinnamate, butylmethoxydibenzoylmethane and homosalate) in environmental samples. The new methodology comprises in-line solid-phase extraction (SPE) of the target analytes by exploiting the bead injection (BI) concept in a mesofluidic lab-on-valve (LOV) format, with subsequent determination by liquid chromatography (LC). The proposed microanalytical system, using a multisyringe burette as propulsion unit, automatically performed the overall SPE steps, including the renewal of the sorbent in each analytical cycle to prevent sample cross-contamination and the post-extraction adjustment of the eluate composition to prevent chromatographic band broadening effects. In order to expedite the LC separation, a C₁₈ monolithic column was applied and an accelerated isocratic elution was carried out by using a cationic surfactant as mobile phase additive. The LOV-BI-LC method was proven reliable for handling and analysis of complex matrices, e.g., spiked swimming pool water and seawater, with limits of detection ranging between 0.45 and 3.2 μg L⁻¹ for 9 mL sample volume. Linear calibration was attained up to 160 μg L⁻¹ for homosalate and up to 35 μg L⁻¹ for the other target analytes, with good reproducibility (RSD < 13%, for 5 different SPE columns). The hyphenated scheme is able to process a given sample simultaneously and within the same time frame than the chromatographic separation/determination of the formerly pre-treated sample, providing concentration values every 9 min. Hence, the sample throughput was enhanced up to 33 times when compared with previously reported off-line SPE methods. A drastic reduction in reagent consumption and effluent production was also attained, contributing to the development of an environment-friendly analyzer.     

Crystallization, mechanical and thermal properties of sorbitol derivatives nucleated polypropylene/calcium carbonate composites

<正>The effect ofαphase nucleating agent(NA) 1,3:2,4-bis(3,4-dimethylbenzylidene) sorbitol(DMDBS) on crystallization and physical properties of polypropylene/calcium carbonate(PP/CaCO_3) composites has been comparatively investigated.Compared with binary PP/CaCO_3 composites,in which CaCO_3 exhibits weak heterogeneous nucleation, inconspicuous reinforcement and toughening effects for PP,the introduction of a few amounts of DMDBS induces a great increase of the degree of crystallinity.Largely improved tensile properties,fracture toughness at relatively higher temperature and heat deformation temperature(HDT) are observed for DMDBS nucleated PP/CaCO_3 composites.     

海泡石对膨胀阻燃聚丙烯燃烧和热分解的影响

将改性后的海泡石添加到聚磷酸铵(APP)和双季戊四醇(DPER)膨胀阻燃聚丙烯(PP/IFR)体系中,采用氧指数(LOI)、热重分析(TGA)、光电子能谱(XPS)、傅里叶变换红外(FTIR)光谱、锥形量热仪(CONE)和扫描电镜(SEM)考察其对膨胀阻燃体系的催化协效作用,探讨作用机理.LOI结果表明,改性的海泡石比纳米水滑石和有机改性的蒙脱土有更好的催化协效作用.CONE数据证实,海泡石可以降低膨胀阻燃聚丙烯体系的热释放速率和总的热释放量.通过观察SEM图片发现,海泡石可以改善膨胀炭层的形貌,提高炭层的隔热隔质性能.TGA结果表明,在氮气和空气气氛下,海泡石均可以提高膨胀炭层的热稳定性,增加高温时残余物的量,其主要作用对象为APP.FTIR和XPS测试发现加热过程中海泡石可以与APP发生化学反应,形成P—O—Si键,增加了APP高温时的稳定性.     

可见/红外宽光谱分色片偏振调控的设计

针对光学系统中可见/红外宽光谱分色片的偏振特性,采用诱导透射法设计了满足偏振遥感光学系统能量要求的可见/红外宽光谱分色片,并对其偏振特性进行了分析.通过计算获得了透射带400～900 nm可见/红外宽光谱分色片的偏振情况,采用等效层理论在其基底背面设计了偏振调控膜系,对分色片透射带的偏振度加以调控.使用needle优化...     

Control of resonant peak depths of tunable long-period fiber gratings using overcoupling

We present a method to reduce changes in the resonant peak depth of a long-period fiber grating (LPFG) as the resonant band is tuned by varying the external refractive index. We theoretically analyze the effects of the initial coupling strength on the peak depth change as external refractive index is varied. By controlling the initial coupling strength, it is experimentally demonstrated that an optimum peak depth can be obtained over a range of operating wavelengths that will maximize the sensitivity and stability of LPFG based sensors and tunable filters.     

About the Stokes decomposition theorem of waves

The Stokes decomposition theorem deals with the electrical field of a light beam. The theorem asserts that a beam can be viewed as the sum of two differently polarized parts. This result was recently discussed for light in the frame of the unified theory of coherence. We study the general case of an electromagnetic wave which can be in radio, radar, communications, or light. We assume stationary components with any power spectrum and finite or infinite bandwidth. We show that an accurate definition of polarization and unpolarization is a key parameter which rules the set of solutions of the problem. When dealing with a “strong definition” of unpolarization, the problem is treated in the frame of stationary processes and linear invariant filters. When dealing with a “weak definition”, solutions are given by elementary properties of bidimensional random variables.     

Sixth moment optimization of multi-channel Bragg filters

The design of multichannel optical filter is studied theoretically. New efficient two-step method based on combination of 6-th moment minimization and straightforward numerical minimization is developed. It is applied to find a fiber Bragg grating profile with minimal refractive index variation for 5 ÷ 32 channels. Obtained results are closer to the theoretical limit than previously reported.     

最优折衷三元相位振幅滤波器设计

 为了使在空间光调制器上易于实现的三元相位振幅滤波器在畸变容限、噪声抑制能力和相关峰尖锐度这3个指标上均能取得较好的性能,在最优折衷最大相关高度滤波器的基础上提出了最优折衷三元相位振幅滤波器,并研究了其设计方法。它只需最大化单个准则就能确定最优的临界线角度和支撑区域,简化了优化设计过程。实验结果表明：与二元纯相位滤波器相比,这种滤波器对于在30°的旋转畸变范围内并存在复杂背景的目标能给出更尖锐的相关峰。这将提高相关峰探测的准确性。     

Deodorisation effect of diamond-like carbon/titanium dioxide multilayer thin films deposited onto polypropylene

Many types of plastic containers have been used for the storage of food. In the present study, diamond-like carbon (DLC)/titanium oxide (TiO₂) multilayer thin films were deposited on polypropylene (PP) to prevent flavour retention and to remove flavour in plastic containers.For the flavour removal test, two types of multilayer films were prepared, DLC/TiO₂ films and DLC/TiO₂/DLC films. The residual gas concentration of acetaldehyde, ethylene, and turmeric compounds in bottle including the DLC/TiO₂-coated and the DLC/TiO₂/DLC-coated PP plates were measured after UV radiation, and the amount of adsorbed compounds to the plates was determined. The percentages of residual gas for acetaldehyde, ethylene, and turmeric with the DLC/TiO₂ coated plates were 0.8%, 65.2% and 75.0% after 40 h of UV radiation, respectively. For the DLC/TiO₂/DLC film, the percentages of residual gas for acetaldehyde, ethylene and turmeric decreased to 34.9%, 76.0% and 85.3% after 40 h of UV radiation, respectively. The DLC/TiO₂/DLC film had a photocatalytic effect even though the TiO₂ film was covered with the DLC film.