Determination of personal care products in water using UHPLC–MS after solid phase extraction with mesoporous silica‐based MCM‐41 functionalized with cyanopropyl groups

A silica‐based MCM‐41 mesoporous material functionalized with cyanopropyl groups has been synthesized by cocondensation, characterized and applied to preconcentrate six parabens and three UV filters in river and swimming‐pool waters. The analytes were quantified by ultra‐high performance liquid chromatography‐tandem mass spectrometry, according to the Directive 96/23/EC. Even though matrix effect was negligible, quantification in river water samples with the standard addition approach improved the recoveries obtained using solvent‐based and even with matrix‐matched calibration. The method quantification limits in river water samples were 0.05 ng/mL for 2,4‐dihydroxybenzophenone and 0.01 ng/mL for the rest. Recoveries, evaluated for a concentration level of 0.5 ng/L, were in the range 93.5‐107.6% for parabens and in the range 64.2‐85.8% for UV filters, with relative standard deviations intraday ≤10.2 and 10.8%, respectively. This parameter, evaluated for a concentration level of 0.1 ng/L, ranged between 98.3 and 110.4% for parabens and between 61.9 and 89.9% for UV filters, with relative standard deviation intraday ≤15.3 and 15.5%, respectively. The two UV filters with lower recoveries were the most affected by the addition of sodium chloride. River and swimming pool waters were analyzed and all the personal care products were found in the swimming pool water, whereas only methylparaben was detected in the river water.     

适用于雷达系统的高温超导窄带滤波器

对雷达系统,通过在接收前端安置高Q、窄带、高带外抑制的滤波器,可以有效减少信号间的干扰,由此可见高性能的滤波器对于雷达系统来说,具有重要作用.与常规滤波器相比,高温超导滤波器具有带边陡峭、插入损耗小、带外抑制高、可以设计极窄带等特点.在本文中,我们设计加工了一种高性能的12阶切比雪夫(Chebyshev)高温超导带通滤波器,其中心频率为1341兆赫兹、带宽为5.035兆赫兹,可用于雷达系统.在滤波器设计中,我们用Sonnet软件对滤波器进行了仿真计算.最后滤波器在以氧化镁为衬底的双面超导薄膜上制作,衬底直径为2英寸、厚度为0.5毫米.测试结果表明,该滤波器符合设计要求,具有很好的选择性和带外抑制.     

Ce3(PO4)4在酸性溶液加热条件下化学形态转化及机理研究

磷酸高铈(Ce3(PO4)4)是一种难溶于水的化合物,本文测定磷酸高铈在常温pH=0.4的Ksp值为1~8×10-34,但在测定过程中发现Ce3(PO4)4的溶解度受温度变化的影响较大,尤其在50℃以上时,Ce3(PO4)4饱和溶液体系中的Ce4 、PO43-和pH值均变化异常。根据测得的Ce4 、PO43-浓度以及pH值,推断出50℃以上时Ce3(PO4)4转化为Ce(HPO4)2,并建立了相应的转化机理,测定出Ce(HPO4)2的Ksp为3~7×10-13。     

连续结构微带滤波器的矩阵运算法分析

用矩阵运算法对“均匀”和“等比”两种连续结构的带阻及低通滤波器进行了研究,分析了结构参数对滤波器性能的影响.实际制作并测试了滤波器,理论与实验结果基本一致.     

Self-assembling and phase coexistence of SW trimers as complex amphiphile analogues. I. Simulations

We analyse by discrete molecular dynamics the self-assembly of SW trimer particles that contain a different number of attractive and repulsive spheres. They also have different geometries: linear, obtuse, rectangular and equilateral. We identify that some of these molecules exhibit liquid–vapour equilibria while others do not. For all of them, we show the morphological phase diagram built up from the different supra-molecular structures formed by each type of trimer. We simulated 14 different systems with a total of 321 states. The main features of the supra-molecular structures depend only on the composition and geometry of the trimer: triple SW trimers do not form supra-structures, double SW trimers and single SW trimers form monolayers, bilayers and worm-like micelles. The liquid–vapour coexistence properties are also exhibited. These trimers can be used to model complex amphiphiles beyond the standard ones, such as the Gemini and the Bola surfactants as well as colloidal particles.     

Improving signal-to-noise ratio for the forensic analysis of glass using micro X-ray fluorescence spectrometry

Micro X-ray fluorescence spectrometry (μXRF) is a standard technique used for the elemental analysis of glass fragments in forensic casework. The glass specimens encountered in casework are usually small (<1 mm), thin fragments that are partially transparent to the exciting X-ray beam. In addition to providing fluorescence from the small glass fragments, the primary beam X-rays can scatter within the chamber and provide noise in the measurements. To reduce scatter from the sample stage, the fragments are typically mounted on a thin plastic film and raised on an XRF sample cup (≤3 cm in height). However, at these heights, there may still be significant scatter from the sample stage, which adversely affects the signal-to-noise ratio (SNR) and the limit of detection (LOD). A plastic mount was designed and 3D-printed in-house to allow fragments to be raised as high as possible from the sample stage, thereby minimizing stage scatter. Most elements detected in glass showed an improvement in the SNR when using the 3D-printed mount for analyses. The greatest improvement (>30%) was observed for lower atomic number elements (Na and Mg) and higher atomic number elements (Sr and Zr). Another simple method to improve SNR is the use of primary beam filters; when using primary beam filters during analyses, elements with characteristic lines in the high-energy range (Rb, Sr, and Zr) showed the greatest improvement (>70%) in SNR. The impact of both strategies for the improvement of SNR is presented here.     

Comparative study of pretreatment methods for the determination of metals in atmospheric aerosol by electrothermal atomic absorption spectrometry

A comparative study of pretreatment methods for the determination of 10 elements (As, Cd, Pb, V, Ni, Mn, Cr, Cu, Fe, Al) in atmospheric aerosols by electrothermal atomic absorption spectrometry (ETAAS) was conducted. For the digestion of the particulates collected in filters, six methods were compared using a mixture of HNO₃ and HF with or without the addition of various oxidative agents (HClO₄ or H₂O₂) or acids (HCl). The comparative study was performed using loaded cellulose filter samples, which were digested in Parr bombs and heated in a conventional oven at 170 °C for 5 h. The extraction efficiency and blanks were compared and it was proved that the digestion method using only HNO₃–HF extracted most of the metals and gave the lowest blanks. The HNO₃–HF mixture was selected for the development of an improved microwave digestion method specific for aerosol-loaded filters. The operating parameters were optimized, so that quantitative recovery of the reference materials NIST 1649a urban dust and NIST 1648 urban particulate matter was achieved. The blank of cellulose and teflon filters were also determined and compared. Teflon filters present the lowest blanks for all the elements. The obtained limits of detection for each type of filters were adequate for environmental monitoring purposes. ETAAS instrumental operation was also optimized for the compensation and the elimination of interferences. The temperature optimization was performed for each metal in every type of filter and optimized parameters are proposed for 10 elements.     

气相色谱-质谱法测定水体中5种典型有机紫外防晒剂

建立了水体中5种典型有机紫外防晒剂甲氧基肉桂酸乙基己酯（ethylhexyl methoxycinnamate,EHMC）、二苯酮-3（benzophenone-3,BP-3）、4-甲基苄亚基樟脑（4-methylbenzylidene camphor,4-MBC）、奥克立林（octocrylene,OC）和胡莫柳酯（homosalate,HMS）的气相色谱-质谱检测方法。对HMS、BP-3衍生化条件进行了系统的优化。以100 μL双（三甲基硅烷基）三氟乙酰胺（N,O-bis（trimethylsilyl） trifluoroacetamide,BSTFA）为衍生化试剂,在100 ℃下反应100 min。水样固相萃取选用Oasis HLB萃取柱（0.5 g）,洗脱溶剂为乙酸乙酯-二氯甲烷（1：1,v/v）,水样pH 3~5。该方法对5种化合物的检出限范围为0.5~1.2 ng/L,定量限范围为1.4~4.0 ng/L。最佳实验条件下,加标水样回收率为87.85%~102.34%,相对标准偏差（n=3）均小于5%。该方法成功地应用于昆明市第一污水厂进出口水样中目标物质的分析。     

自组装金纳米粒子涂层对环境水样中紫外线吸收剂的固相微萃取

以刻蚀不锈钢丝为基体,采用化学沉积法在表面沉积金纳米粒子(AuNPs),修饰一层1,8-辛二硫醇分子后,再自组装一层AuNPs,制备了高强度AuNPs涂层固相微萃取(SPME)纤维,并与HPLC联用,以常用紫外线吸收剂为例,评价了AuNPs-SPME纤维的萃取分离性能。当萃取时间为30 min、温度为55℃、搅拌速率为800 r/min,pH=7时,萃取效果最好。在优化的萃取条件下,所建立的Au NPs-SPME-HPLC法测定4种紫外吸收剂(2-羟基-4-甲氧基二苯甲酮、2-乙基己基-4-(N,N-二甲氨基)苯甲酸酯、2-乙基己基-4-甲氧基肉桂酸酯和2-乙基己基水杨酸)的线性范围为0.004~200μg/L,检出限为0.43~570 ng/L(S/N=3),相对标准偏差(RSD)在1.9%~4.2%(n=5)之间。河水、废水处理厂的废水以及雨水样品中紫外线吸收剂的加标回收率在77.9%~108%之间,RSD为3.1%~8.0%(n=5)。     

TiO2形态结构与光催化活性关系的研究

本文介绍了TiO2多相光催化剂的作用机理及其结构特性对光催化活性的影响，并对TiO2的品相组成、品粒尺寸、比表面积、表面形态与光催化活性的关系作了综述。