Profiling of thermally aged EPDM seals using portable NMR,indenter measurements and IR spectroscopy facilitating separation of different deterioration mechanisms

The changes occurring in EPDM cable transit seals during thermal ageing and the causes of these changes were investigated. Samples were aged at a temperature of 170 °C, and subsequently evaluated with respect to the distance from the surface with modulus profiling, infrared (IR) spectroscopy and nuclear magnetic resonance (NMR) spectroscopy, based on the extractable mass fraction profiles for initial and aged materials. The ageing resulted in an increase in the modulus and in the degree of oxidation and in a decrease in the NMR transverse relaxation time, T₂. The NMR data were obtained in a non-invasive manner by ex situ experiments performed with a portable low-field spectrometer (NMR MOUSE). The results showed deterioration processes that can be attributed to different mechanisms i.e. oxidation, anaerobic crosslinking and migration of oil extender. The unique combination of parameter profiles made it possible to resolve and quantify these three contributing mechanisms. The NMR results highlight the potential of this method for on-site testing.     

Deterioration of highly filled EPDM rubber by thermal ageing in air: Kinetics and non-destructive monitoring

The effects of air ageing at different temperatures between 110 and 170 °C on cable transit seals based on highly filled EPDM rubber used in nuclear power plants were studied. The changes of the macroscopic mechanical properties (Young's modulus, indentation modulus and strain-at-break) were in accordance with the Arrhenius equation with an activation energy of 110 kJ mol⁻¹. Profiling to assess the structure and property gradients within aged blocks was performed via IR spectroscopy, micro-indentation, gravimetric analysis of n-heptane-extracted samples and non-invasive portable NMR spectroscopy. A previously developed methodology was used to separate the deterioration into three different processes: polymer oxidation that was diffusion-limited at all temperatures, migration of low-molar-mass species to the surrounding media and anaerobic changes to the polymer network. The methodology allowed the assessment of the kinetics (rate as a function of time and temperature) of the different processes. It was noticed that polymer oxidation yielded more crosslinking at higher temperatures than at lower temperatures. The data obtained by both the portable NMR (a non-invasive method) and the indentation modulus profiling showed correlations with strain-at-break data, indicating their usefulness as condition monitoring methods.     

Forensic Applications of Portable X‐ray Fluorescence Spectrometer: Glass Samples

Portable X‐ray Fluorescence Spectrometer (PXRF) is a qualitative and semi‐quantitative elemental analysis method. Recently, many researches using PXRF in the elemental analysis of materials have been reported. However, PXRF has not been extensively applied in forensic science, thus this study is devoted to demonstrate the utility of this technique through a rapid elemental analysis of glass samples for preliminary glass discrimination. Major elements such as Si, O, Ca, Al, and Na, as well as traces of Sr, Rb, K, Fe and Sn, in 25 glass samples were analyzed by PXRF. The amounts of some elements, such as Fe, K, Zr, and Sr, vary in different samples, while other elements, such as Th, are consistent in most tested glass samples. The results show that we can discriminate 98.31 % of 7,500 pair‐wise comparisons created from 25 glass samples. This study establishes PXRF as a new rapid method for the preliminary elemental analysis of glass, which shows a potential to be further applied for discrimination of glass samples in forensic field.     

基于Android平台的便携式痕量重金属离子检测仪的研制

基于Android平台,设计了一种用于痕量重金属离子检测的便携式电化学分析检测仪。仪器输出电压范围为-3~3 V,精度为0.1%,分辨率<1 mV;电流检测范围为-10~10 mA,精度为0.1%,最小分辨率为10 pA,已达到普通电化学分析的要求。借助Android智能设备在人机交互方面的优势,仪器设有专业检测模式与快速检测模式,简化了复杂的电化学检测分析过程,可同时满足专业用户与普通用户的操作需求。使用本仪器,并结合商品化的电极对Cu, Cd, Pb及Hg等常见的重金属离子进行了初步检测,线性范围、重复性及结果准确度方面都获得了满意的结果。     

On‐site sampling and sample‐preparation approach with a portable sampler based on hollow‐fiber/graphene bars for the microextraction of nitrobenzene compounds in lake water

A novel on‐site sampling and sample‐preparation approach was developed and evaluated in the present work. In this procedure, hollow‐fiber/graphene bars (HF/GBs) were used for sampling and sample preparation. A handheld battery‐operated electric egg beater was utilized to support the HF/GBs and stir the sample solution to facilitate extraction at the sampling site. Four nitrobenzene compounds (nitrobenzene, o‐nitrophenol, m‐nitrophenol, and p‐nitrophenol) were used as model compounds. Several factors affecting performance, including types and amount of graphene used and extraction and desorption times, were investigated and optimized in the laboratory. Under optimized conditions, the enrichment factors of the four nitrobenzene compounds ranged from 46 to 69. Good linearities of 0.01–10 μg/mL with regression coefficients between 0.9917 and 0.9973 were obtained for all analytes. The LOD of the method was 0.3 ng/mL. Satisfactory recoveries (98–102%) and precision (1.0–5.8%) were also achieved. The ultrastructures and extraction mechanism of the HF/GBs were characterized and analyzed. The proposed approach coupled with high‐performance liquid chromatography was successfully applied in the extraction and determination of trace nitrobenzene compounds in lake water. Experimental results showed that the approach is simple, convenient, rapid, and practical for routine environmental monitoring.     

便携式中波近红外光谱仪在线无损检测生鲜猪肉胆固醇

应用便携式近红外光谱仪采集320份生鲜猪肉在近红外光谱中波区的光谱信息,采用不同优化方法建立猪肉胆固醇预测模型,并对异常样品的剔除及组合预处理方法对模型性能的改善进行了分析。研究表明：通过对异常值的二次剔除,并使用SG一阶导数(savitzky-golay first derivative, SG 1stD)、SG平滑(savitzky-golay smoothing, SGS)和正交信号校正(OSC)的组合预处理方法,可获得最佳生鲜猪肉胆固醇预测模型,其参数如下：校正集相关系数(R_c)=0.9137,校正标准差(standard error of calibration, SEC)=2.5607,验证集相关系数(R_p)=0.656 7,预测标准差(standard error of prediction, SEP)=4.985 5,主因子数(principal factor, PF)=4,范围误差比(ratio of performance to standard deviation, RPD)=2.5032,相对预测标准差(relative standard error of prediction, RSEP)=8.625 4%,SEP/SEC=1.946 8,说明模型在近红外光谱中波区对猪肉胆固醇的分辨能力和预测准确度较好,通过向校正集中补充代表性样品可使模型稳健性进一步改善。对检验集样品预测值(prediction value, PV)与参比值(reference value, RV)的t检验显示二者之间无显著性差异(p＞0.05),检验集样品总体预测准确率为62.5%,其中50～70 mg·(100 g)-1区段的局部预测准确率达到91.7%,可以用于生鲜猪肉胆固醇浓度的在线快速初步定量分析。该研究将便携式近红外光谱用于在近红外中波区对生鲜猪肉及肉制品中胆固醇浓度的分析和检测,通过进一步的研究和改进,可将其应用于产品的原料分级、品质和过程控制及市售产品的抽检等。     

实现大气压负直流辉光放电的针-柱电极结构设计与实验

为了实现大气压环境下稳定的辉光放电,设计了一种新型的针-柱电极结构放电装置。采用针尖直径为56.4 μm的不锈钢针作为放电阴极,直径为4 mm的紫铜圆柱作为放电阳极,两者通过精密机械结构保持平行。当针-柱之间间距为2 mm、镇流电阻10 MΩ,放电电阻10 MΩ,测试电阻1 kΩ、放电电压-2 740 V、大气压环境、室温、无外部通入气流时,针-柱之间实现了稳定的辉光放电。示波器存储的放电波形和数码相机记录的放电图像验证了从电晕放电到辉光放电,再到火花放电的三种放电模式。该针-柱结构易于用MEMS工艺加工制作,可应用于便携式分析仪器中作为离子源使用。     

溶解氧的快速现场测定

水体中存在的分子态氧被称为溶解氧 ( Dissolved oxygen,DO) .在环境保护工作中 ,DO是一个特别重要的指标 ,它可以直接反映水体污染的程度 [1] 和评判海水的新鲜程度[2 ] ,同时 ,DO是构建环境质量评价模型的重要参数和基础 [3] .在工业上 ,DO是有机生态肥料生产工艺过程和产品质量控制中的重要指标 [4 ] ,也是金属防腐工作中需要监测的重要参数 [5] .在生命科学中 ,DO还是反映细胞新陈代谢等重要生命活动的基本参数 [6 ] .因此 ,溶解氧的测定具有重要意义 .测定溶解氧的常用方法有碘量法及其修正法 [1,7] 、电化学方法 [8,9] 等 .这些…     

Rapid detection of organophosphorus pesticide residue on Prussian blue modified dual-channel screen-printed electrodes combing with portable potentiostat

A new method consisted of a dual-channel screen-printed electrode (DSPE) efficient modified with Prussian blue and acetylcholinesterase was developed for the rapid detection of organophosphorus pesticide residues.     

基于X射线荧光光谱仪的儿童沙坑重金属污染特征调查研究

儿童沙坑是学龄前儿童重要的户外游乐场所,同时具有较好的雨水下渗性能,导致伴随周边地表径流而来的污染物容易在其中富集。因此儿童在沙坑内玩耍时,面临重金属类污染物进入体内的健康风险。研究利用X射线荧光光谱法(XRF)快速、无损的检测特点,对北京市儿童沙坑重金属污染特征进行调查。结果表明：(1)XRF对自制标准试样中Pb, Cu, As和Cd的测量值与理论值的准确度为-1.3%～7.5%,精确度在1.1%～5.3%范围内,均符合相关环境质量检测技术规范中规定的仪器检测准确度和精密度要求(均小于10%);(2)4种重金属测量值与理论值之间均呈现极显著正相关关系(p<0.001),其决定系数(R²)分别为0.999, 0.999, 0.996和0.998,基于结果建立了测量值和理论值的拟合方程;(3)应用XRF对北京市17家公园和13个居民小区内儿童沙坑重金属含量进行测定,两组样点中Pb和As含量差异显著,而Cu和Cd含量无显著差异。4种重金属标准差的变异系数范围在0.24～0.43,其中除Cd的变异系数小于0.3外,其余重金属均大于0.3,表明空间变异明显;(4)与...