A new instrument to measure gaseous nitrous acid (HONO) in the atmosphere

A new in situ instrument (LOPAP: long path absorption photometer) to measure gaseous nitrous acid (HONO) using wet chemical sampling and photometric detection has been developed. This instrument is aimed to overcome the known problems with current HONO measurement techniques and was designed to be a cheap, sensitive, compact, and continuouslyworking HONO monitorfor ambient air measurements in the troposphere or for measurements of higher concentrations e.g. in smog chambers, in exhaust gases, and in indoor environments. Laboratory investigations were carried outto characterize the instrument components with respect to collection efficiency, optimum dye formation, optimum detection, and interfering species. Detection limits ranging from approximately 3 to 50 pptV have been obtained with response times from 4 to 1.5 min, respectively, using different instrument parameters. The accuracy of the measurements is in the range between +/-(10-15)%. The validation of the instrument was performed in the laboratory for HONO concentrations of 3 and 30 ppbV using ion chromatography and with a DOAS (differential optical absorption spectrometer) instrument in a large outdoor smog chamber in the range from 0.1 to 20 ppbV. The deviations were well within the errors of the measurements; however, when comparing the data with the DOAS instrument systematically higher values were found with the LOPAP instrument.     

Mobile laboratory with rapid response instruments for real-time measurements of urban and regional trace gas and particulate distributions and emission source characteristics

Recent technological advances have allowed the development of robust, relatively compact, low power, rapid response (approximately 1 s) instruments with sufficient sensitivity and specificity to quantify many trace gases and aerosol particle components in the ambient atmosphere. Suites of such instruments can be deployed on mobile platforms to study atmospheric processes, map concentration distributions of atmospheric pollutants, and determine the composition and intensities of emission sources. A mobile laboratory containing innovative tunable infrared laser differential absorption spectroscopy (TILDAS) instruments to measure selected trace gas concentrations at sub parts-per-billion levels and an aerosol mass spectrometer (AMS) to measure size resolved distributions of the nonrefractory chemical components of fine airborne particles as well as selected commercial fast response instruments and position/velocity sensors is described. Examples of the range of measurement strategies that can be undertaken using this mobile laboratory are discussed, and samples of measurement data are presented.     

A practical alternative to chemiluminescence-based detection of nitrogen dioxide: cavity attenuated phase shift spectroscopy

We present results obtained from a greatly improved version of a previously reported nitrogen dioxide monitor (Anal Chem. 2005, 77, 724-728) that utilizes cavity attenuated phase shift spectroscopy (CAPS). The sensor, which detects the optical absorption of nitrogen dioxide within a 20 nm bandpass centered at 440 nm, comprises a blue light emitting diode, an enclosed stainless steel measurement cell (26 cm length) incorporating a resonant optical cavity of near-confocal design and a vacuum photodiode detector. An analog heterodyne detection scheme is used to measure the phase shift in the waveform of the modulated light transmitted through the cell induced by the presence of nitrogen dioxide within the cell. The sensor, which operates at atmospheric pressure, fits into a 19 in.-rack-mounted instrumentation box, weighs 10 kg, and utilizes 70 W of electrical power with pump included. The sensor response to nitrogen dioxide (calculated as the cotangent of the phase shift) is demonstrated to be linear (r2 > 0.9999) within +/- 1 ppb over a range of 0-320 ppb (by volume). The device exhibits a detection limit (3sigma precision) of less than 60 parts per trillion (0.060 ppb) with 10 s integration, a value derived from measurements at NO2 concentration levels of both 0 and 20 ppb; the detection limit improves as the integration time is increased to several hundred seconds. The observed baseline drift is less than +/- 0.5 ppb overthe course of a month. An intercomparison of measurements of ambient NO2 concentrations over several days using this sensor with a quantum cascade laser-based infrared absorption spectrometer and a standard chemiluminescence-based NOx analyzer is presented. The data from the CAPS sensor are highly correlated (r2 > 0.99) with the other two instruments. The absolute agreement between the CAPS and each of the two other instruments is within the expected statistical noise associated with the infrared laser-based absorption spectrometer (+/- 0.3 ppb with 10 s sampling) and chemiluminescence analyzer (+/- 0.4 ppb with 60 s averaging). The major limitation concerning accuracy is a direct spectral interference with phototchemically produced 1,2-dicarbonyl species (e.g., glyoxal, methylglyoxal). However, this interference can be readily removed by shifting the detection band to a slightly longer wavelength and ensuring that the lower edge of the detection band is greater than 455 nm.     

自动测厚技术在国产绝缘纸板生产线湿操机上的应用

该文介绍了安装在绝缘纸板生产线湿操机上检测湿纸板厚度的精密仪器一激光测厚仪的使用方法、自动控制工作原理及程序设计。采用了市场上的通用器件如逻辑控制器PLC、模拟量块、激光测厚仪等,分析了它的工作原理和使用效果。对于国产湿操机的湿纸测厚技术通过自主技术改造、设计和编程,已经达到了精确测量湿纸厚度的要求。从运行上看,即便于操作,又提高了工艺流程和产品质量的稳定性。实践证明,这种实用的测厚技术完全可以替代昂贵的进口测厚技术。     

球磨处理对藜麦淀粉结构和特性的影响

为了研究球磨处理对藜麦淀粉结构的影响,采用X-射线衍射仪、激光粒度仪及傅里叶红外光谱仪等对淀粉颗粒的结构进行分析,并对改性后的藜麦淀粉特性进行了进一步研究。结果表明,球磨处理可显著减小藜麦淀粉粒径,降低藜麦淀粉的结晶度,使淀粉无序化程度增加。球磨处理后,藜麦淀粉吸水指数由1.84%提高到3.13%,溶解度由8.50%提高到19.60%,膨胀度和凝胶强度也显著增大,而析水率由41.62%降低到30.10%。该研究可为藜麦淀粉的开发利用提供一定的参考。     

EVALUATION OF THE VOLAND-STEVENS LFRA TEXTURE ANALYZER FOR MEASURING THE STRENGTH OF PECTIN SUGAR JELLIES

The Voland-Stevens LFRA texture analyzer was compared to the Tarr-Baker gelometer for its applicability to measuring jelly strength. Both instruments showed a linear relationship between jelly break strength and pectin content. The test results from the two instruments were highly correlated (r = 0.94). The coefficient of variation relative to the overall average of measurement was 5.0% for the Voland-Stevens LFRA and 8.4% for the Tarr-Baker gelometer. The Voland-Stevens LFRA instrument may be equal to or better than the Tarr-Baker gelometer for measuring jelly break strength. It offers the advantages of reduced errors in sample preparation and ease of instrument calibration.     

Time resolved characterization of diesel particulate emissions. 1. Instruments for particle mass measurements

The measurement of diesel vehicle exhaust particulate mass is currently accomplished using filter collection methods according to the Code of Federal Regulations (CFR). Such filter methods limit time resolution to a minimum of several minutes, making it impossible to study emissions during transient operating conditions. Extensive testing of five different measurement methods has demonstrated that fast response measurements of diesel exhaust particulate mass concentrations, consistent with CFR filter measurements, are feasible using existing technology. The measurement principles of choice are the real time weighing of exhaust samples as implemented in the tapered element oscillating microbalance (TEOM) and the measurement of light scattering from exhaust particles as implemented in the DustTrak nephelometer. Each of these two instruments has distinctive strengths. The TEOM excels in the area of constant calibration, independent of vehicle. For the DustTrak, this calibration varies by vehicle. On the other hand, the DustTrak has an excellent signal-to-noise ratio, freedom from interference due to other exhaust sample properties, good time resolution, and simplicity. The strengths of the two measurement methods are complimentary, so an obvious suggestion is to integrate them. The nephelometer would obtain a fast response signal, with near real time calibration provided by the microbalance.     

An absolute calibration for gas-phase hydroxyl measurements

We describe a new method of calibrating tropospheric hydroxyl (OH) instruments. Ozone-alkene mixtures produce steady-state OH radical concentrations. The steady state is governed by competition between OH production in the reaction of ozone with the alkene and OH removal by reactions with the alkene, ozone, and the reactor wall. In a flowtube reactor transporting an ozone-alkene mixture, the OH wall loss rate can be measured by varying the alkene concentration. Delivery of the reaction mixture to the sampling entry of an atmospheric OH measurement instrument provides an absolute calibration of the instrument's response to OH. The present precision of calibration is +/-8% (1-sigma), based on reproducibility over a wide range of ozone concentrations. The accuracy (+/-43%) is limited by uncertainties in kinetic rate coefficients and OH yield, which can be improved. The calibration requires no photon flux measurements or lamp-dependent absorption coefficients, which have inherent, variable, systematic uncertainties, and it has been tested in field experiments.     

二氧化钛水热改性涤/棉混纺织物的自清洁性能

为赋予涤/棉混纺织物光催化自清洁性能,基于水热合成技术,分别使用钛酸四丁酯、硫酸钛以及硫酸氧钛在涤/棉混纺织物表面负载纳米TiO₂颗粒,借助扫描电子显微镜、X射线衍射仪、傅里叶变换红外光谱仪、热重分析仪和紫外-可见光漫反射光谱仪等对TiO₂改性涤/棉混纺织物的结构和性能进行分析,比较了不同种类TiO₂前驱体改性涤/棉混纺织物可见光下降解污物的自清洁能力。结果表明:较钛酸四丁酯和硫酸钛改性的涤/棉混纺织物,硫酸氧钛改性涤/棉混纺织物接枝的锐钛矿型TiO₂颗粒多且尺寸小,光吸收能力增强,禁带宽度减小,其光催化自清洁性能优异,5次洗涤后自清洁性能没有明显减弱。     

Modified versus producer milk calibration: mid-infrared analyzer performance validation

Our objective was to determine the validation performance of mid-infrared (MIR) milk analyzers, using the traditional fixed-filter approach, when the instruments were calibrated with producer milk calibration samples vs. modified milk calibration samples. Ten MIR analyzers were calibrated using producer milk calibration sample sets, and 9 MIR milk analyzers were calibrated using modified milk sample sets. Three sets of 12 validation milk samples with all-laboratory mean chemistry reference values were tested during a 3-mo period. Calibration of MIR milk analyzers using modified milk increased the accuracy (i.e., better agreement with chemistry) and improved agreement between laboratories on validation milk samples compared with MIR analyzers calibrated with producer milk samples. Calibration of MIR analyzers using modified milk samples reduced overall mean Euclidian distance for all components for all 3 validation sets by at least 24% compared with MIR analyzers calibrated with producer milk sets. Calibration with modified milk sets reduced the average Euclidian distance from all-laboratory mean reference chemistry on validation samples by 40, 25, 36, and 27%, respectively for fat, anhydrous lactose, true protein, and total solids. Between-laboratory agreement was evaluated using reproducibility standard deviation (s_R). The number of single Grubbs statistical outliers in the validation data was much higher (53 vs. 7) for the instruments calibrated with producer milk than for instruments calibrated with modified milk sets. The s_R for instruments calibrated with producer milks (with statistical outliers removed) was similar to data collected in recent proficiency studies, whereas the s_R for instruments calibrated with modified milks was lower than those calibrated with producer milks by 46, 52, 61, and 55%, respectively for fat, anhydrous lactose, true protein, and total solids.     

湿法消解-火焰原子吸收法测定小麦粉中锌含量的不确定度评定

目的评定湿法消解-火焰原子吸收法测定小麦粉中锌含量的不确定度。方法依据JJF 1059.1-2012《测量不确定度评定与表示》,分析小麦粉中锌含量测定过程中的不确定度来源,通过建立数学模型,确定不确定度传播律,量化各不确定度分量,然后计算合成不确定度和扩展不确定度。结果本研究测得的小麦粉中锌的含量为(16.1±0.8)mg/kg,k=2。测定过程的不确定度来源主要有测量结果的重复性、方法的回收率、由校准曲线求得的样品溶液中Zn浓度、样品溶液的定容体积、试样称样量和样品空白变动性引入的不确定度分量。结论湿法消解-火焰原子吸收法测定小麦粉中锌含量的不确定度主要来源于方法的回收率,其次为由校准曲线求得的样品溶液中Zn浓度和测量结果的重复性引入的不确定度,其他因素的影响相对较小。     

水中总有机碳溶液标准物质的研制

目的研制一种适用于相关检测仪器校准及分析方法评价的国家有证标准物质。方法经过标准物质原材料的选择、特性量值的测量方法、标准物质的制备方法、均匀性检验、12个月稳定性考察以及定值测量,并对样品的均匀性、测量的分散性及其他因素引入的不确定度分量分析和确定后,计算得到水中总有机碳标准物质测量过程不确定度的合成结果。结果水中总有机碳溶液标准物质的均匀性良好,稳定性优异,标准值定值结果为1000mg/L,相对扩展不确定度为2%。该标准物质已获批国家二级标准物质,编号为:GBW(E)082426。结论该标准物质性能良好,可满足食品、药品、日化、环境保护及化工产品研究和检测的需要,可用于相关仪器(总有机碳分析仪)的校准、分析方法评价,为统一相关量值发挥应有的作用。     

超高分子量聚乙烯纤维的热力学稳定性能

针对超高分子量聚乙烯(UHMWPE)纤维熔点低、易蠕变等不足,以油田井下作业环境为测试条件,研究了UHMWPE纤维在干热和湿热状态下的力学稳定性能,借助差示扫描量热仪、热重分析仪、扫描电子显微镜、X射线衍射仪和电子能谱分析仪,表征并分析了UHMWPE纤维的热学性能和微观结构。结果表明:UHMWPE纤维表面在热和处理液的刻蚀作用下产生明显的沟槽;在相同的温度下处理,湿热状态下纤维的力学性能损失比干态下小,尤其在70 ℃下湿热连续处理30 d,纤维强力下降率基本控制在6%以内;对纤维进行干热处理,当温度接近纤维熔点时,随着温度的升高,纤维强力下降明显,140 ℃下干热处理1 h,强力最大下降率达19.87%。     

原子吸收分光光度计法测定圆白菜中镉含量的不确定度

目的评定原子吸收分光光度计法(atomic absorption spectroscopy,AAS)测定圆白菜中的镉含量的不确定度。方法依据JJF 1059.1-2012《测量不确定度评定与表示》,分析整个检测过程中所产生的不确定度来源,计算合成不确定度。结果计算得出圆白菜中镉的含量为0.036 mg/kg,扩展不确定度为0.0046 mg/kg(包含因子k=2)。结论可通过控制标准曲线校准过程和加强对仪器的维护保养等措施来减小原子吸收分光光度法测定圆白菜中镉含量的不确定度,保证实验数据的可靠性,为检测报告提供有力依据。     

食品中水分含量测定装置的研究现状

食品中水分含量是食品质量控制的一个重要指标,对其测定的装置可分为直接测定装置和间接测定装置,如直接测定装置中的干燥器、干燥箱、蒸馏装置、卡尔费休水分测定仪、卤素水分测定仪、红外水分测定仪、微波水分测定仪;间接测定装置中的阿贝折射仪、阻容法水分测定仪、近红外成分分析仪、核磁共振仪、高光谱成像系统。本文对食品中水分含量测定装置的基本结构,测定原理,应用和优缺点等方面进行了综述,为食品中水分含量测定装置的选择和使用提供参考。     

仲钨酸铵（APT）中温还原制取粗晶钨粉

以仲钨酸铵（APT）为原料,加入添加剂Li、Na盐在1000℃湿氢条件下还原制得粗晶钨粉。通过SEM、XRD和激光粒度仪对粗晶钨粉形貌、物相组成及粒度分布进行表征。研究了还原温度,时间,Li、Na盐的种类及含量对钨粉粒度的影响。结果表明,采用APT为原料,Li2CO3为添加剂,在1000℃,180min湿氢条件下,直接还原制备出了流动性良好、结晶完整的粗晶钨粉,平均粒径≥40μm。     

An optical flow injection analysis system for measurement of glucose in tomato

An optical flow injection analysis (FIA) system for glucose measurement in tomato was constructed by using a glucose oxidase (GOD) immobilized reactor and a photodiode sensor, a peristaltic pump and a personal computer. The GOD reactor was crammed with strip-shaped of a GOD immobilized membrane to an acrylic pipe. The GOD was immobilized on polytetrafluoroethylene membrane by crosslinking with glutaraldehyde. Hydrogen peroxide generated by the GOD reaction oxidized luminol to produce chemiluminescence in the presence of horseradish peroxide. The chemiluminescence was detected by using the photodiode. The glucose measurement system was calibrated with standard glucose solutions. The calibration range of the system for glucose was 2.0–100.0 mmol L⁻¹. Measurement time for every sample was within 3 min. Glucose concentrations of a fresh and processed tomato samples measured with this glucose measurement system could be evaluated rapidly and non-laboriously.     

A procedure for the determination of lead in green vegetables at concentrations down to 1 microgram/kg

An accurate and highly sensitive dry ashing/graphite furnace atomic absorption spectrometry (GFAAS) procedure has been developed for the measurement of lead in green vegetables. The accuracy of the method was established by analysis of standard reference materials and confirmed by isotope dilution using an inductively coupled plasma-mass spectrometer (ICP-MS). The limit of detection (wet weight) of the technique is 1-3 micrograms/kg with relative standard deviations ranging from 6% for a sample of kale containing 500 micrograms/kg to 20% for cabbage containing 3.0 micrograms/kg.     

电感耦合等离子体质谱法在食品中重金属检测中的应用

重金属元素是食品安全领域重要的检测项目,目前,用于检测重金属的仪器主要有原子吸收光谱仪、原子荧光光谱仪、电感耦合等离子体发射光谱仪、电感耦合等离子体质谱仪(inductively coupled plasma mass spectrometer,ICP-MS)等。ICP-MS具有线性范围宽、灵敏度高、精密度好、检出限低、可同时分析多种元素等优点,广泛应用于医学、生物学、食品安全等多种领域。本文综述了近年来电感耦合等离子质谱法在食用油、面制品、乳及乳制品、水产品、果蔬及其他食品检测中的应用,并对该领域的发展前景进行了展望,以期为ICP-MS技术测定食品中重金属的检测发展提供一定的参考价值。     

云南元江红宝石的宝石学特征研究

采用常规的宝石学研究方法以及电子探针、扫描电镜、电子顺磁共振、傅里叶变换红外光谱仪和拉曼光谱仪等现代测试仪器,对云南元江红宝石的宝石学特征进行了较全面的分析。结果表明,元江红宝石颜色丰富,裂理发育,内含有大量的包裹体,主要致色离子为Cr,随着Cr质量分数的增高,红色逐渐加深,折射率增大;其拉曼光谱在200~1 200 cm-1范围内有2~3个拉曼吸收峰,红外光谱除2 110,1 980 cm-1红外吸收双峰外,还出现381,420,647 cm-13个Al2O3的特征峰。