Coating of Sol–Gel Film on Silver Nanodendrite as a Novel Solid-Phase Microextraction Fiber for Determination of Volatile Aldehydes in Edible Oils

In this work, a novel solid-phase microextraction fiber was fabricated by a new substrate applied for quantitative analysis of trace volatile aldehydes emitted during thermal oxidation of edible oils, analyzed by GC–MS. Ag nanodendrites as a porous substrate, spontaneously coated on a Cu wire, and polydimethylsiloxane/polyethylene glycol (PDMS/PEG) were deposited onto the substrate by sol–gel dip-coating. Parameters affecting the extraction efficiency, such as the substrate porosity, extraction time and temperature, and desorption time and temperature were investigated and optimized. The desorption temperature was chosen as 260 °C, and desorption time was set at 3 min. Results shows that extraction efficiency of sol–gel coating deposited on Ag nanodendrite substrate is meaningfully higher than that of deposited on bare Cu wire. Under the optimum conditions, the limits of detection (LODs) ranged between 0.5 to 0.2 μg/L. The relative standard deviations including repeatability (within fibers) and reproducibility (between fibers) varied between 7.5–11.2 and 9.3–16.2%, respectively.     

A New Analytical Method to Volatile Compounds in Cider Apples: Application to Evaluate the Starch Index

Headspace solid-phase microextraction coupled to Fast gas chromatography (GC) with flame ionization detector and with quadrupole mass spectrometric detector was employed to study the volatile compounds in Asturian cider apples. The best conditions used for volatile analysis of apple were: sample equilibration at 25 °C for 60 min, followed by polydimethylsiloxane-divinylbenzene fiber exposure to the headspace above the sample for 5 min, and finally thermal desorption of the adsorbed substances in the injector port for GC analysis. The use of Fast gas chromatography allowed the separation of 24 compounds in less than 8 min, reducing the analysis time in 80% compared with conventional gas chromatography. The aromatic profile of 26 crushed apple samples included in Designation of Origin Cider from Asturias was analyzed. The chemometric technique named multiple linear regression allowed us to establish a relationship between apple volatile compounds and the starch index. The results obtained are consistent with the known apple ripening model.     

Determination of Vanillin and Ethyl-Vanillin in Milk Powder by Headspace Solid-Phase Microextraction Coupled with Gas Chromatography-Mass Spectrometry

A method for determination of vanillin and ethyl-vanillin in milk powder by auto headspace solid-phase microextraction (SPME) coupled with gas chromatography-mass spectrometry (GC-MS) was established. Vanillins in sample were extracted with SPME through a fused-silica fiber coated with divinylbenzene/polydimethylsiloxane. The analytes were desorbed by GC at 260 °C for 5 min and separated on a DB-5MS capillary column and detected by MS with EI source by selected ion monitoring mode (EI-SIM). As a result, the limit of detection of vanillin and ethyl-vanillin was 0.1 and 0.05 mg/kg. The spiked recovery was between 90.0 and 100 %, and the RSD ranged from 1.9 to 5.1 % (n?=?6). This method eliminated the interferences from complicated matrix effectively. The method was successfully applied for quick determination of vanillin and ethyl-vanillin content in milk powder samples.     

超低碳不锈钢三角丝生产工艺研究

介绍了超低碳不锈钢三角丝的研制与开发，讨论了超低碳不锈钢三角丝的加工工艺，通过试验确定了最佳工艺，从而成功地生产出１．９４ｍｍ×１．０５ｍｍ和３．８０ｍｍ×１．７０ｍｍ两种三角丝。     

Quantification of Six Phthalates and One Adipate in Luxembourgish Beer Using HS-SPME-GC/MS

A simple, low-cost and sensitive method for the determination of six phthalate acid esters (dimethyl phthalate, diethyl phthalate, dibutyl phthalate, benzyl butyl phthalate, bis(2-ethylhexyl) phthalate and dioctyl phthalate) and one adipate (bis(2-ethylhexyl) adipate) in beer has been developed using head-space solid-phase microextraction (HS-SPME) followed by gas chromatography coupled to mass spectrometry (GC/MS). SPME conditions were optimised, and optimum extraction parameters were found to be 95 °C at 100 min, without addition of NaCl. Matrix interference was avoided by using a deuterated internal standard (ISTD). Limits of detection ranged from 0.006 to 0.590 μg/L. The method showed good linearity with coefficients of determination ranging from 0.963 to 0.999 and satisfactory accuracy (74–101 %) and repeatability (3.56–27.86 %) values. The method was applied to 15 samples of beer from Luxembourgish breweries, stored in different containers (can, glass and aluminium bottle), and phthalates were detected in all samples with concentrations as high as 61.56 μg/L for total phthalates. The exact origins of phthalates in beer were difficult to determine from the data in this study, though the brewing and bottling process seems to be a major contributor.     

几种电磁屏蔽面料屏蔽效能的研究

选择铜镍涂层织物、银纤维交织织物、铜镍金属丝织物、不锈钢交织织物4种电磁屏蔽面料进行研究,利用同轴传输线法测试它们的电磁屏蔽效能。结果表明:材料中的金属丝比例越大,织物的电导率越大,电磁屏蔽效果越好。在金属丝含量相同的情况下,银丝的电磁屏蔽性能优于不锈钢。经洗涤后,银纤维交织织物和不锈钢交织织物的电磁屏蔽效果没有明显变化,而铜镍涂层织物和铜镍金属丝织物的电磁屏蔽性能均有明显衰减。     

不锈录井钢丝的评估与试制

介绍国内外不锈录井钢丝分类、使用状况以及试制技术指标,对高品质不锈录井钢丝进行评估,并试制Sw960,Sw970两种牌号不锈录井钢丝。根据合金元素含量及其组合匹配,分析提高不锈录井钢丝综合性能,尤其是耐应力腐蚀破断能力水平的方法;从控制固溶处理工艺与拉拔工艺出发,找出钢丝在拉拔过程中防止脆断的途径;探讨碳含量对奥氏体铬镍钼不锈钢录井钢丝腐蚀性能的影响,结果表明,试制的不锈录井钢丝抗拉强度和显微硬度较低,韧性较好;显微组织与进口不锈录井钢丝相似;对腐蚀介质H2S耐应力腐蚀开裂能力与国外产品水平相当。     

涤纶/碳纳米管柔性发热丝的制备及其性能

针对现有发热丝柔性差、不耐水洗等问题,提出在涤纶纱线表面均匀涂覆碳纳米管的柔性发热丝制备方 法。依据柔性发热丝制备工艺要求,设计了可在纱线表面均匀涂覆碳纳米管的实验系统。利用该系统在涤纶纱线 表面进行均匀涂覆碳纳米管实验研究,并对所制备的发热丝进行电阻测量、微观形貌观察及发热性能测试。结果 表明：采用这个实验系统可实现柔性发热丝的制备;长度为15 cm的发热丝平均电阻率为24.895 Ω·cm,标准偏差 为0.473 Ω·cm;微观形貌照片显示涤纶纱线表面均匀涂覆了一层网状结构碳纳米管材料;在施加36 v 电压下构建 的并联网状结构表面4 min内可获得50.3 ℃的加热温度。     

金属针布专用钢丝球化退火工艺研究

对SWRH72B、金属针布专用合金钢A和B 3种钢丝的球化退火工艺进行研究。结果表明:Φ2.15 mmSWRH72B钢丝的最佳球化温度为(700±5)℃,保温时间在120 m in左右;Φ3.50 mm合金钢A和Φ3.80 mm合金钢B钢丝最佳球化温度都为(710±5)℃,前者保温时间为160~180 m in,后者为180~240 m in,退火后碳化物球粒度都可以达到3.5~4.0级。     

顶空固相微萃取分析白酒香气物质的条件优化

利用顶空固相微萃取与气质联用相结合的方法分析白酒香气物质组成,对影响顶空固相微萃取的操作条件装液量、盐离子浓度、平衡温度、平衡时间、萃取时间和解析时间进行系统地优化.结果表明:项空固相微萃取白酒香气的最佳条件为装液率40%、NaC1质量浓度0.2g/mL,在磁力搅拌加热器上50℃甲衡30min后,萃取头插入样品瓶顶空吸...     

MWCNT-Modified Gold Electrode Sensor for the Determination of Propyl Gallate in Vegetable Oils

A differential pulse voltammetric method for the determination of the synthetic food antioxidant, propyl gallate (PG) was developed. Determination of PG was carried out using multiwalled carbon nanotube (MWCNT)-modified gold electrode (GE) in a solution of 0.1 M acetate buffer (pH 7) as supporting electrolyte. The developed sensor showed an excellent catalytic activity and stability for PG oxidation. Effect of common interfering ions, amount of MWCNT–Nafion suspension, pH of the supporting electrolyte, and scan rate were studied. Under optimized conditions, PG concentration as low as 6.3?×?10^?7 M can be determined in food samples. The determination of PG in vegetable oils with the proposed sensor was in good agreement with those obtained by reported spectrophotometric method.     

Carbon nanotube-polytetrafluoroethylene nanocomposite coating for milk fouling reduction in plate heat exchanger

Cleaning of milk fouling on plate heat exchanger surface causes intermittent downtime to milk processing industry. Fouling occurrence during milk pasteurization potentially reduces the heat transfer rate of plate heat exchanger (PHE), leading to serious energy deficiency. In this study, the development of milk surface foulant was successfully inhibited by superhydrophobic nanoparticulate coating of PHE surfaces. Full dispersion of multiwalled carbon nanotubes (MWCNTs) in hydrophobic polytetrafluoroethylene (PTFE) matrix was completed using ultrasonication and high temperature annealing techniques. Nanomorphology and surface structure of PTFE and CNT-PTFE films on stainless steel surface were interpreted by field emission scanning electron microscope (FESEM). To validate the hydrophobicity of the developed CNT-PTFE nanocomposite coated surface, a water contact angle (WCA) using a simplified sessile drop method, correspondent surface energy, foulant mass, and energy efficiency after milk pasteurization were estimated and compared with stainless steel 316 and polytetrafluoroethylene (PTFE) coated surfaces. Static contact angles for the control, PTFE-coated and CNT-PTFE surfaces increased from 71.2 to 119.6 and 141.1°, respectively. By application of CNT-PTFE nanocomposite coating, the estimated surface energy of heat exchanger surface decreased by 97.0% of its original value. After continuous milk pasteurization for 5 h, the mass of foulant on CNT-PTFE coated heat exchanger surface was 70.3% less than that of the uncoated surface; thus, total energy consumption of test PHE unit also dropped down by 10.2%. Developed CNT-PTFE nanocomposite coated surface will potentially reduce the risk of under-processed milk and decrease the frequency of the routine cleaning-in-place (CIP) program.     

Determination of Total Acid Content in Vinegars by Reaction-Based Headspace Gas Chromatography

This work reports on a simple and efficient method for the determination of total acid content in vinegars by reaction-based headspace gas chromatography. The method is based on the neutralization reaction between the acids in vinegar and carbonate solution in a closed headspace sample vial, from which the carbon dioxide generated from the reaction is analyzed by gas chromatograph equipped with a thermal conductivity detector. The results showed that the headspace equilibration of CO₂ generated from the reaction was achieved in 15 min at 60 °C. The method has a good precision and accuracy, in which the relative standard deviation in the repeatability measurement was 1.73 %, and the relative differences between the data obtained by the headspace gas chromatographic method and the reference titration method were within 4.81 %. The present method is particularly suitable to be used for determining the total acid content of vinegar not only in the process control but also the quality check of point-of-sale samples from commercial markets.     

中日金属制品贸易对比分析及思考

对比分析中日金属制品的进出口品种、国别构成,以及中日钢丝及钢丝绳贸易特点,结果显示:中日都是金属制品贸易大国,2011年中国钢丝及钢丝绳出口额占世界的19.83%,进口额占5.97%;日本分别为6.5%和5.07%。中日是重要的金属制品贸易伙伴:2011年中日钢丝及钢丝绳贸易总量16.5万t,中国是日本合金钢丝第1大出口目的国,碳素钢丝和不锈钢丝的第2大出口目的国;同时中国也是日本进口钢丝绳和不锈钢丝的第1大来源国,碳素钢丝和合金钢丝的第2大进口来源国。虽然中国对日本的钢丝及钢丝绳出口量比从日本进口量大得多,但仍存在贸易逆差。中国应进行产品升级和知名品牌培养。     

Rapid Determination of Titratable Acidity in Wines by Headspace Analysis

This work reports on an automated method for the determination of titratable acidity (TA) of wines by headspace analysis. The method is based on the neutralization reaction between the titratable acids in wines and bicarbonate solution in a closed headspace sample vial from which the carbon dioxide generated from the reaction is detected by gas chromatography (GC). The reaction and headspace equilibration can be achieved within 5 min at 60 °C. The relative standard deviation was 2.1 %, and the detections in spiked samples were in the range of 97.0–104 % of the amount added. Wine samples from the market analyzed by the present method and by the official reference method gave results that the relative differences varied by less than 6.0 % from each other. In sum, the present method is rapid, accurate, and suitable for determining TA in wine in a wide variety of applications from processing to quality control.     

高碳镀锌文胸扁丝生产

高碳镀锌文胸扁丝用以部分取代不锈钢制品制作文胸钢圈。分别采用先镀锌后轧制和先轧制后镀锌2种工艺生产高碳镀锌文胸扁丝。第1种工艺采用循环水冷却,道次压缩率20%左右,钢丝抗拉强度1 800 MPa左右,产品外边缘出现崩锌;第2种工艺采用质量分数为10%左右的乳化液进行润滑,表面清洗后采用垂直出线方式镀锌,钢丝抗拉强度1 800~1 950 MPa,锌层与钢丝结合牢固,通过对收线设备进行改造,异型钢丝的收线盘重提高到300 kg以上。     

电气化铁路接触网补偿钢丝绳的设计与生产

介绍电气化铁路接触网的技术要求和组成,接触网补偿用钢丝绳的材质与结构,接触网补偿钢丝绳尤其是不锈补偿钢丝绳的技术要求,以及我国接触网补偿用钢丝绳的研发状况,要求高碳钢及不锈钢补偿绳疲劳试验后的整绳破断拉力与规定值相比下降分别不超过10%和5%。以12×7+12×3+12×3+1×19W—9.1为例,介绍接触网补偿用钢丝绳的研发:利用串联式变形器一次合绳,钢丝绳为右交互捻,捻距倍数为6.8倍;中心股、内层股、次外层股、外层股的捻距分别为16.8,5.27,.81,7.005mm,直径分别为2.40,.8,1.2,1.79mm,并根据各层股的捻距倍数和捻制系数计算出各层股丝的直径。     

Quantification of furanic compounds in coated deep-fried products simulating normal preparation and consumption: Optimisation of HS-SPME analytical conditions by response surface methodology

The validation of a method for the simultaneous quantification of furanic compounds in coated deep-fried samples processed and handled as usually consumed is presented. The deep-fried food was grinded using a device that simulates the mastication, and immediately analysed by headspace solid phase microextraction coupled to gas chromatography-mass spectrometry. Parameters affecting the efficiency of HS-SPME procedure were selected by response surface methodology, using a 2(3) full-factorial central composite design. Optimal conditions were achieved using 2g of sample, 3g of NaCl and 40min of absorption time at 37°C. Consistency between predicted and experimented values was observed and quality parameters of the method were established. As a result, furan, 2-furfural, furfuryl alcohol and 2-pentylfuran were, for the first time, simultaneously detected and quantified (5.59, 0.27, 10.48 and 1.77μgg(-1) sample, respectively) in coated deep-fried fish, contributing to a better understanding of the amounts of these compounds in food.     

Development of an Electrochemical Sensor for the Determination of Amaranth: a Synthetic Dye in Soft Drinks

The voltammetric behaviour of synthetic food colourant, amaranth, was studied using a multiwalled carbon nanotube (MWCNT) thin film-modified gold electrode in 0.1 M acetate buffer solution of pH 5.0. A well-defined oxidation peak was obtained for amaranth at 0.792 V with the modified electrode. The diffusion controlled oxidation of amaranth at the modified electrode can be attributed to the electrocatalytic nature of MWCNT, since the bare electrode has not produced an electrochemical signal under the same experimental conditions. The operational parameters such as supporting electrolyte, pH of the solution and amount of MWCNT–Nafion suspension were optimised. Under optimum conditions, the oxidation peak current varies linearly with concentration in the range from 1.0?×?10^?5 M to 1.0?×?10^?6 M with a limit of detection at 6.8?×?10^?8 M. The developed sensor has good sensitivity and selectivity towards oxidation of amaranth. The sensor was successfully employed for the determination of amaranth in three different samples of soft drinks, and the results were in good agreement with the standard spectrophotometric method.