高锰酸钾法测定四氧化二氮纯度的超差原因及正方法

根据液体火箭推进定型文件—《四氧化二氮技术条件》,四氧化二氮纯度测定方法为高锰酸钾滴定法 ,取样方式采用干冰取样法或充氮取样法。实践中化验结果经常出现超差 ( <0 .3% )。已做过的研究对负超差尚无明确结论 ,对正超差较普遍认为 ,参加滴定反应的硫磷混酸中含有还原性物质。但实际上 ,即使用完全合格的硫磷混酸 ,超差仍然存在。针对这一问题 ,本文从理论和实验两方面得出了无论是正超差 ,还是负超差 ,主要在于计算安瓿球中四氧化二氮的取样量时 ,忽略了取样前后安瓿球内空气质量的变化对取样准确性的影响 ,给试样质量带来了相当于取样…     

高锰酸钾法测定四氧化二氮纯度的超差原因及修正方法

根据液体火箭推进定型文件-<四氧化二氮技术条件>,四氧化二氮纯度测定方法为高锰酸钾滴定法,取样方式采用干冰取样法或充氮取样法.     

天然气组成分析取样装置的研制

研制了一种天然气组成分析的取样装置.该装置主要由注水部分、取样部分、固定部分组成.注水与取样的分离设计,实现一次性全密封取样,可解决普通针筒注射器抽取样品易混入空气,造成气体不纯,针筒内残余水分对组分结果产生误差等问题.通过进行21次天然气组成分析比对试验,比较使用普通针筒注射器与新型取样装置的天然气组成分析结果,证明...     

四氧化二氮微量水标准物质的研制

以四氧化二氮为原料,经预脱水、深度脱水和精馏等处理工艺制备了7种浓度的四氧化二氮微量水标准物质.两家实验室采用核磁共振方法对标准物质中的微量水含量进行定值分析.用方差统计方法对定值结果进行数据处理和不确定度评定.     

在线测量发酵液葡萄糖浓度的过滤取样探头的研制

设计了一种罐内快速过滤取样探头,以解决在线测量发酵参数过程中的发酵液连续取样问题。此探头由支撑体、旋塞阀、O型圈、过滤膜管、管盖组成,可以直接插入发酵罐内,能够承受发酵前期的灭菌高温,并能避免取样时杂菌入侵发酵液。过滤膜采用筒状陶瓷膜,罐内发酵液经错流过滤,可由蠕动泵抽取适量无菌的渗透液给分析仪。利用此装置对葡萄糖溶液进行了取样测试,结果表明,此装置适用于发酵液在线取样,取样速率为3.0 mL/min,葡萄糖透过率保持100%,探头引起的时间延迟约为2 min。     

流体熵相关性质的Monte Carlo模拟新方法

提出了用于计算实际体系熵相关性质的Monte Carlo 多级取样分子模拟方法.应用这一方法,对硬球流体的化学势及Helmholtz 自由能进行了估算,得到了满意的结果.计算化学势时,不存在通常试验粒子方法所遇到的高密度问题.该方法特别适合规律性的系统研究,较之普通模拟方法要有效得多.模拟得到的硬球体系无限稀释组份的超额化学势与对比直径的关系,在相变区域为一条双凹曲线;无论是在相变区还是在单相区,Carnahan-Starling 公式对这一关系的描述均有较大偏差.     

流体熵相关性质的Monte Carlo模拟新方法

提出了用于计算实际体系熵相关性质的Monte Carlo多级取样分子模拟方法. 应用这一方法, 对硬球流体的化学势及Helmholtz自由能进行了估算, 得到了满意的结果. 计算化学势时, 不存在通常试验粒子方法所遇到的高密度问题. 该方法特别适合规律性的系统研究, 较之普通模拟方法要有效得多. 模拟得到的硬球体系无限稀释组份的超额化学势与对比直径的关系, 在相变区域为一条双凹曲线; 无论是在相变区还是在单相区, Carnahan-Starling公式对这一关系的描述均有较大偏差.     

微量滴定装置及滴定分析微量化初探

设计了一种简易的微型化滴定分析装置，取样量仅需１～２ｍｌ，滴定操作简便，易于操作，而且可节省滴定剂。其滴定分析的准确度、精密度与常规方法相当。     

纺丝浴成分在线自动分析装置及分析方法等

公布号：CN105334287A
　　公布日：2016.02.17
　　申请人：唐山三友集团兴达化纤有限公司
　　摘要：一种纺丝浴成分在线自动分析装置,包括人机操作单元、电气控制单元、取样单元、分析单元和自动清洗单元,取样单元包括取样杯、取样电磁阀和蠕动泵;所述分析单元包括搅拌器、pH计和两个标准液储罐;人机操作界面与电气控制单元连接,电气控制单元分别与电磁阀、搅拌器、蠕动泵和pH计连接。这种纺丝浴成分的自动分析装置和方法,不仅能够对纺丝浴成分实现在线自动分析,还能对其设备进行在线自动冲洗,无需人工现场取样,降低工人劳动强度,提高工作效率和安全系数,计算比对测量,免去人工测量误差,提高测量精准度,适合各规模的纺丝企业使用。     

不稳定的溶剂配位有机金属化合物单晶取样技术

不少有机金属化合物,特别是有机稀土金属化合物对微量空气、湿气极为敏感,因而它们的取样和分析技术具有一定的特殊性,并有专门介绍这方面技术的报道。最近我们得到一个四氢呋喃配位的有机镥配合物,它在四氢呋喃溶剂中能生成带溶剂配位的无色斜方晶体。当抽去溶剂或在通氩下,将晶体装入玻璃毛细管时,由于晶体在离开母液后失去配位溶剂分子而变成粉状,因而采用一般的取样方法得不到适用于x-射线晶体结构测定的单晶。为此,我们设计了一种新的单晶取样器(见附图),可以成功地取出单晶样品,并测定其晶体结构。该取样器加工简便,取样安全可靠,可连续取样,以便挑选合适的测试样品。现将装置及取样方法介绍于后。     

Polycyclic aromatic hydrocarbons in the atmosphere: monitoring, sources, sinks and fate. I: Monitoring and sources

This is the first of a series of two papers intended to review the state-of-the-art knowledge on atmospheric PAHs, concerning their monitoring, sources and transformation processes in the atmosphere. The monitoring section briefly introduces this class of compounds, mainly focusing on the 16 PAHs indicated by the US-EPA as priority pollutants. These compounds undergo partitioning between the gas phase and particulate, which has to be considered in the choice of the sampling methodology. Furthermore, sampling artifacts may arise from further phase transfers inside the sampling device. After sampling, extraction, clean up and detection/quantification procedures will follow. They are closely related since the choice of the extraction technique will heavily condition the clean-up step, and both procedures will place demands on the performance of the detection technique (usually GC-MS or HPLC). This is particularly true in the case of complex samples such as those arising from atmospheric sampling. The sources of atmospheric PAHs are then discussed with a particular focus on receptor models, which can allow the apportionment of PAH sources based on concentration data that can be routinely obtained by pollution control networks.     

Time-weighted average water sampling with a diffusion-based solid-phase microextraction device

A new diffusion-based solid-phase microextraction (SPME) time-weighted average (TWA) field water sampling device was developed and investigated by field trial. The sampler is constructed with copper tube and caps and a commercial SPME fiber assembly. The device possesses all advantages of SPME; it is solvent-free, reusable, combines sampling, isolation and enrichment into one step, and the fiber can be directly injected into a gas chromatograph for analysis with a commercial SPME fiber holder, without further treatment. Field trials in Laurel Creek (Waterloo, Ont., Canada) and Hamilton Harbour (Hamilton, Ont., Canada) illustrated that the device is durable, easy to deploy, and the mass uptake of the device is independent of the face velocity. The device provides good precision [relative standard deviations (RSDs) are less than 20%] and the data obtained with this device are quite comparable to those obtained with the spot sampling method, which demonstrates that the newly developed SPME water sampling device is suitable for long-term monitoring of organic pollutants in water.     

The active and passive sampling of benzene, toluene, ethyl benzene and xylenes compounds using the inside needle capillary adsorption trap device

A new and simple method of solventless extraction of volatile organic compounds (VOCs) from air is presented. The sampling device has an adsorbing carbon coating on the interior surface of a hollow needle, and is called the inside needle capillary adsorption trap (INCAT). This paper describes a study of the reproducibility in the preparation and sampling of the INCAT device. In addition, this paper examines the effects of sample volume in active sampling and exposure time in passive sampling on the analyte adsorption. Analysis was achieved by sampling the air from an environmental chamber doped with benzene, toluene, ethyl benzene and xylenes (BTEX) compounds. Initial rates of adsorption were found to vary among the different compounds, but ranged from 0.0099 to 0.016 nmol h(-1) for passive sampling and from 2.2 to 10 nmol h(-1) for active sampling. Analysis was done by thermal desorption of the adsorbed compounds directly into a gas chromatograph injection port. Quantification of the analysis was done by comparison to actively sampled activated carbon solid phase extraction (SPE) measurements.     

渗透实验装置的改进与研究

介绍了一款简单实用的U形管渗透装置。装置包括U形管和底座2个部分,U形管底部利用了磨口连接设计,可随时拆卸,拆开后可在内部用硅胶垫片固定半透膜。整套装置操作简单易行,已获得国家实用新型专利,并转化为产品,有望成为渗透实验教学的常用装置。     

An improved Sampling Strategy for the Measurement of VOCs in Air,Based on Cooled Sampling and Analysis by Thermodesorption-GC-MS/FID

Abstract

Reliable and comprehensive sampling methods are required to obtain accurate data for VOC concentrations in air samples. The major drawback of the adsorption tube sampling method, widely employed in environmental studies, is the fact that C₂ compounds are usually not trapped quantitatively.

The focus of this work was thus to improve sampling based on adsorption tubes packed with Molsieve and Carbosieve. To improve the sampling efficiency for the C₂ compounds, a cooling device, based on Peltier cooling was constructed, which could be operated at a temperature down to ?30°C.

Experiments under laboratory and field conditions were carried out to study the influence of the sampling temperatuie on the recovery of ethane and ethene as the most volatile VOCs. The results clearly demonstrate the need for a cooled sampling device for the analysis of C₂ compounds in air. Under the investigated conditions, the recoveries with ambient temperature sampling were only in the range of 38–46% for ethane and 33–59% for ethene respectively, in comparison to the cooled sampling device. These findings are only valid for the described conditions and can change significantly with temperature and concentration. A generalisation of the recovery is thus very difficult to give.

The use of the sampling device for a field study is reported, where samples were collected simultaneously at three different altitudes in a diurnal profile on the slope of the Schulterberg mountain in Tyrol (Austria).     

A microchip-based endothelium mimic utilizing open reservoirs for cell immobilization and integrated carbon ink microelectrodes for detection

This paper describes the fabrication and characterization of a microfluidic device that utilizes a reservoir-based approach for endothelial cell immobilization and integrated embedded carbon ink microelectrodes for the amperometric detection of extracellular nitric oxide (NO) release. The design utilizes a buffer channel to continuously introduce buffer or a plug of stimulant to the reservoir as well as a separate sampling channel that constantly withdraws buffer from the reservoir and over the microelectrode. A steel pin is used for both the fluidic connection to the sampling channel and to provide a quasi-reference electrode for the carbon ink microelectrode. Characterization of the device was performed using NO standards produced from a NONOate salt. Finally, NO release from a layer of immobilized endothelial cells was monitored and quantified using the system. This system holds promise as a means to electrochemically detect extracellular NO release from endothelial cells in either an array of reservoirs or concurrently with fluorescence-based intracellular NO measurements.     

Solid-phase microextraction coupled to gas chromatography with flame ionization detection for monitoring of organic solvents in working areas

A solid-phase microextraction (SPME) method was developed for air monitoring of organic solvents frequently used in chemical laboratories (namely pentane, dimethyl ether, acetone, acetonitrile, dichloromethane, hexane, ethylacetate, tetrahydrofurane, cyclohexane, benzene, and toluene). SPME sampling conditions and chromatographic separation were optimised. Linearity of response for each component of the mixture was tested. Standard solutions containing all the compounds, at three different concentrations, were analysed in triplicate and the relative standard deviations (RSDs) were calculated. The method was applied to the monitoring of indoor air in a research chemical laboratory. An SPME fibre was used as a sampling device inside the laboratory. Moreover an SPME fibre was used as a portable sampling device in order to determine the effective human exposure. Comparison of the portable and fixed sampling device showed differences in the amount of solvents associated with activities performed nearby.     

Dynamic liquid phase nanoextraction coupled to GC/MS for rapid analysis of methoxyacetophenone and anisaldehyde isomers in urine

This study introduces a novel extraction technique in the nanoscale and challenges the limits of solvent extraction in the GC/MS using electronic ionization (EI) method for quantitative determination of six methoxyacetophenone (MAP) and anisaldehye (AAH) isomers in one drop of water and urine. This technique is termed as dynamic liquid phase nanoextraction (DLPNE). The optimum parameters for the DLPNE technique were: selection of solvent, toluene; sampling volume, 0.44 microL; dwell time, 2 s; number of sampling, 15; extraction time, 1.5 min; volume of extraction solvent, 60 nL; and no salt addition. The LODs for this technique were 5-20 ng/mL. The RSDs were in the range of 9.7-12.6% (n = 6). The linear dynamic range of the calibration curve of DLPNE is from 0.02 to 0.5 microg/mL with correlation coefficient (r(2)) >0.9705. The advantages of the DLPNE technique are rapidity, ease of operation, simple device, and extremely little solvent and sample consumption. This technique was also compared with the static liquid phase nanoextraction (SLPNE) while the SLPNE failed to detect any signal for the six isomers. We believe that this technique can be very useful for the detection of volatile organic compounds in environmental science from microscale of water or it can be applied to clinical or pharmaceutical application such as diagnosis of microamount of urine or blood samples by GC/MS.     

Corrosion problem in headspace gas chromatography with phase reaction conversion technique

This paper reports a corrosion problem in the headspace sampling needle when using a phase reaction conversion headspace gas chromatographic method in Agilent headspace auto-sampler. The examination by microscopy shows that corrosion mainly takes place on the surface of the outer wall of the needle that is exposed to the air during each headspace sampling. Since it was proven that the helium flushing is effective in minimizing the pit type of corrosion on the stainless needle material, a custom-made surface flushing device was proposed for corrosion inhibition.     

Poly(dimethylsiloxane)-based microfluidic device with electrospray ionization-mass spectrometry interface for protein identification

An easy method to fabricate poly(dimethylsiloxane) (PDMS)-based microfluidic chips for protein identification by tandem mass spectrometry is presented. This microchip has typical electrophoretic microchannels, a flow-through sampling inlet, and a sheathless nanoelectrospray ionization (ESI) interface. The surface of the microchannel was modified with 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) and the generated electroosmotic flow under acidic buffer condition used for the separation was found to be more stable compared to that generated by the microchannel without modification. The feasibility of the device for flow-through sampling, separation, and ESI-MS/MS analysis was demonstrated by the analysis of a standard mixture composed of three tryptic peptides. Results show that four peaks corresponding to three peptide standards and acetylated products of the standard peptide were well resolved and the deduced sequences were consistent with those expected. Furthermore, the compatibility of this device with other miniaturized devices to integrate the whole process was also explored by connecting a miniaturized enzymatic digestion cartridge and a desalting cartridge in series to the sampling inlet of the microchip for the identification of a model protein, beta-casein.