新型二氧化碳被动采样器的研制

研究了一种新型二氧化硫被动采样器。考察了无纺布、定性滤纸和定量滤纸等吸收剂的载体在相同情况下对二氧化硫和二氧化氮的吸收效果，对吸收载体进行了优选。并针对低温地区和高温高湿的气候条件，确立了以三乙醇胺（TEA）为吸收主体，分别以乙二醇、丙三醇为添加剂的吸收体系。     

新型二氧化硫被动采样器研制成功

北京化工大学理学院石美等人在前人工作的基础上,对二氧化硫被动采样器的吸收层进行了改进,研制了一种新型二氧化硫被动采样器。考察了无纺布、定性滤纸和定量滤纸等吸收剂的载体在相同情况下对二氧化硫和二氧化氮的吸收效果,对吸收剂的载体进行了优选,确定了以无纺布作为     

滤纸上化学实验的研究

以滤纸为载体,在滤纸上进行的化学实验可较大程度减少试剂用量,且无废水排放等环境问题,是绿色化学的典范,值得研究、提倡与推广。     

液膜萃取本地产烟叶中烟碱的研究

采用液膜萃取技术对本地产烟叶的烟碱进行了分析,膜载体使用0.45 μm的PVC油膜和定性滤纸,浸泡膜载体的溶剂分别使用十一烷,十六烷和CHCl3.液膜萃取后的样品经GC/MS分析表明,滤纸作为膜载体的萃取效率明显高于PVC油膜;相同膜载体的情况下,以CHCl3浸泡的膜载体的萃取效果比较好.文中还对两种膜载体在不同溶剂浸泡下的烟碱的萃取效率以及最佳萃取时间进行了研究.     

钍试剂滴定法测定硫化催化裂化烟气中二氧化硫和三氧化硫的含量

采用3个吸收瓶和1个缓冲瓶串联同时采集硫化催化裂化烟气中的二氧化硫和三氧化硫,以高氯酸钡标准溶液为滴定剂,钍试剂为指示剂滴定分析吸收液中硫酸根的浓度,计算得到FCC烟气中二氧化硫和三氧化硫的含量。方法可应用于炼油厂的现场采样分析。     

离子色谱法测定气体中痕量二氧化硫

建立了测定气体中痕量二氧化硫的离子色谱法。采用氢氧化钠–过氧化氢溶液为吸收液,将气体样品中痕量二氧化硫转化为硫酸根离子,以离子色谱法测定硫酸根离子,从而得到气体中二氧化硫含量。二氧化硫气体含量在1~100μL/L范围内与色谱峰面积线性关系良好,相关系数为0.999 9。二氧化硫的检出限为0.1μg/L,测量结果的重复性小于2%(n=6),测定标准样品的回收率在98.1%~99.6%之间,准确度优于对照方法。     

滤纸上的氧化还原反应实验

在中学化学实验教学中,一般用试管实验验证元素及其化合物的性质.该方法实验现象明显,操作简单,但试剂用量大导致实验成本高并加重了环境污染.广大的化学教育工作者提出了"点滴板实验"、" 微型实验" 等简单、高效、环保的新方法[1~6] .笔者以氧化还原反应为例,介绍了一种类似的新方法——滤纸实验（以滤纸为载体,在滤纸上即可完成的实验）.该方法不仅操作简单,实验现象明显,而且环保、经济.     

固相吸光光度法的现状与展望

固体载体萃取光度法,作为痕量分析的一个分支正在逐渐兴起,逐步形成了具有一套理论指导的测试方法。自80年代以来,以树脂相、泡沫塑料、滤纸、凝胶相和萘相为载体的光度法,齐头并进,各具特色。以几种物质为载体进行测定的离子已有10多种,其共同的优点是:使分离、富集和测定合为一体,大大提高了灵敏度。与一般的溶液光度法相比,灵敏度提高1～2个数量级。现分别介绍如下:     

亚甲蓝褪色光度法测定二氧化硫

１引言 大气环境是人类赖以生存的必要条件。保护和改善大气环境质量,对于促进生产建设、发展科学技术、保障人民健康都有十分重要的意义。因此,大气质量监测就显得异常重要。在大气污染中二氧化硫含量的高低是衡量大气质量的重要指标之一。目前,监测大气二氧化硫的主要方法是四氯汞钾溶液吸收一盐酸副玫瑰苯胺比色法和甲醛缓冲溶液吸收－盐酸副玫瑰苯胺比色法。其它研究过的方法还有气体传感器法、气态分子吸收法等。我们利用二氧化硫的还原性,在较强酸性介质中,使亚甲基蓝还原为无色溶液,以此建立了直接测量大气二氧化硫的新方法,…     

基于邻苯二甲醛-NH_3-Na_2SO_3反应的固相荧光分析方法测定水样中的氨氮

基于邻苯二甲醛(OPA)-NH3-Na2SO3体系的荧光反应,以滤纸为固相载体,建立了检测水样中氨氮的固相荧光分析新方法。对滤纸的浸泡时间、反应液的p H值、反应时间等实验参数进行了优化,优化结果为:滤纸的最佳浸泡时间为4 h以上;反应液的适宜p H值为11.5~13.0;反应平衡时间为165 min。在优化实验条件下,方法的线性范围为2.00~12.0μmol/L;检出限为0.746μmol/L;泉水和河水的基底加标回收率为89.6%~101.6%。采用该法成功测定了14个河水水样,与靛酚蓝分光光度法测定结果比较,无显著差异。     

Polydimethylsiloxane-based permeation passive air sampler. Part I: Calibration constants and their relation to retention indices of the analytes

A simple and cost effective permeation passive sampler equipped with a polydimethylsiloxane (PDMS) membrane was designed for the determination of time-weighted average (TWA) concentrations of volatile organic compounds (VOCs) in air. Permeation passive samplers have significant advantages over diffusive passive samplers, including insensitivity to moisture and high face velocities of air across the surface of the sampler. Calibration constants of the sampler towards 41 analytes belonging to alkane, aromatic hydrocarbon, chlorinated hydrocarbon, ester and alcohol groups were determined. The calibration constants allowed for the determination of the permeability of PDMS towards the selected analytes. They ranged from 0.026 cm² min⁻¹ for 1,1-dichloroethylene to 0.605 cm² min⁻¹ for n-octanol. Further, the mechanism of analyte transport across PDMS membranes allowed for the calibration constants of the sampler to be estimated from the linear temperature programmed retention indices (LTPRI) of the analytes, determined using GC columns coated with pure PDMS stationary phases. Statistical analysis using Student's t test indicated that there was no significant difference at the 95% probability level between the experimentally obtained calibration constants and those estimated using LTPRI for most analyte groups studied. This correlation allows the estimation of the calibration constants of compounds not known to be present at the time of sampler deployment, which makes it possible to determine parameters like total petroleum hydrocarbons in the vapor phase.     

Solid-phase microextraction under controlled agitation conditions for rapid on-site sampling of organic pollutants in water

An electric drill coupled with a solid-phase microextraction (SPME) polydimethylsiloxane (PDMS) fiber or a PDMS thin film was used for rapid sampling of polycyclic aromatic hydrocarbons (PAHs) in aqueous samples. Laboratory experiments demonstrated that the sampling rates of SPME fiber and thin film can be predicted theoretically. Compared with the SPME fiber, the PDMS thin film active sampler exhibited a higher sampling rate and much better sensitivity due to its higher surface-to-volume ratio and its larger extraction phase volume. The amount of the analytes extracted by the thin film was around 100 times higher than those obtained by fiber, for both 5 min rapid sampling and equilibrium extraction. A new thin film active sampler was then developed for rapid on-site water sampling. The sampling kit included a portable electric drill, a copper mesh pocket, a piece of thin film, and a liner. Laboratory experiments indicated that the sampling remained in the linear uptake phase with this sampler to 8 min for the PAHs. Field test illustrated that this novel sampler was excellent for rapid on-site water sampling due to its short sampling period, high sampling efficiency and durability The thin film sampling kit facilitates on-site sampling, sample preparation, storage and transport. This new sampler is more user-friendly and easier to commercialize than previous samplers.     

Analysis of volatile organic compounds in human urine by headspace gas chromatography-mass spectrometry with a multipurpose sampler.

A multipurpose sampler (Gerstel MPS), designed for liquid large volume, gaseous and headspace samples was used for the GC-MS analysis of organic volatiles in human urine. Headspace sampling with a volume-, temperature- and speed-controlled gas-tight syringe was combined with a temperature-controlled cold injection system (CIS) for cold trapping, enrichment and focusing of analytes. Regular 2-ml GC vials filled with 1 ml acidified urine were used as headspace sampling vials. A 100-vial autosampler tray was equipped with an additional temperature and heating time controlled "preheating station" for five vials. Profiles of organic volatiles in human urine were determined and 34 components identified. Trimethylamine (TMA) and 4-heptanone as two metabolites of medical interest were quantified. Calibration curves and intra assay imprecision for 4-heptanone concentrations in the range of 40 to 800 ng/ml showed a correlation coefficient of r = 0.9980 and a relative standard deviation (RSD) between 3.0 and 3.4%. Calibration curves and intra-assay imprecision for TMA concentrations in the range of medical interest from 0.5 to 20 micrograms/ml showed a correlation coefficient of r = 0.9968 and a RSD between 4.1 and 6.8%. The high practicability of the multipurpose sampler for both gaseous and liquid samples together with the here shown good reproducibility and sensitivity make this single CIS-GC-MS system very attractive for routine clinical use in metabolic profiling of organic volatiles (headspace) and non-volatiles (liquid).     

Evaluation of a passive air sampler for measuring indoor formaldehyde.

A passive air sampler, using 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole, was evaluated for the determination of formaldehyde in indoor environments. Chromatography paper cleaned using a 3% hydrogen peroxide solution was experimentally determined as being the optimum absorption filter for the collection of formaldehyde (0.05 microg cm(-2) formaldehyde). From a linear-regression analysis between the mass of formaldehyde time-collected on a passive air sampler and the formaldehyde concentration measured by an active sampler, the sampling rate of the passive air sampler was 1.52 L h(-1). The sampling rate, determined for the passive air sampler in relation to the temperature (19 - 28 degrees C) and the relative humidity (30 - 90%), were 1.56 +/- 0.04 and 1.58 +/- 0.07 L h(-1), respectively. The relationship between the sampling rate and the air velocity was a linear-regression within the observed range. In the case of exposed samplers, the stability of the collected formaldehyde decreased with increasing storage time (decrease of ca. 25% after 22 days); but with the unexposed samplers the stability of the blank remained relatively unchanged for 7 days (decrease of ca. 37% after 22 days). The detection limits for the passive air sampler with an exposure time of 1 day and 7 days were 10.4 and 1.48 microg m(-3), respectively.     

Elemental characterization of TSP and two size fractions of airborne particulate matter from Tehran by INAA and AAS

Airborne particulate matter has been collected by a high volume and a Gent-type stacked filter unit (SFU) low volume sampler during the 2000-2001 period. The high volume sampler used S&S cellulosic and the SFU two Nuclepore polycarbonate filters to collect fine and coarse size fractions. The elemental analysis of the collected TSP, fine and coarse particles has been performed using instrumental neutron activation analysis and atomic absorption spectrometry. Twenty-two trace elements on Nuclepore and twenty-four elements on S&S filters have been measured. The collected data have been compared with the previous data of Tehran air and with other cities in the world. This revised version was published online in July 2006 with corrections to the Cover Date.     

热解析低温等离子体电离源用于糯高粱中农药残留的快速筛查

本研究设计并搭建了一套热解析低温等离子体电离源(TD-LTP),与质谱联用实现了糯高粱中农药残留的快速和高灵敏检测.TD-LTP由热解析装置和低温等离子体放电源两部分组成,农药残留样品首先在热解析进样器内汽化,再由载气载带进入等离子体区域被电离.热解析进样器使LTP产生的气相等离子体与样品之间的气-固或气-液相互作用转变为气-气相互作用,大大提高了难挥发样品(如农药)的电离效率;电离源与质谱进样口之间采用同轴连接,提高了离子的利用率和传输效率.与传统的LTP电离源相比,TD-LTP电离源的灵敏度提高了8倍以上,稳定性提高了4倍.本研究对热解析低温等离子体电离源的各参数进行了优化,并与自制的矩形离子阱质谱相结合,研究了12种农药在该电离源下的特征离子.最后,将此电离源与商品化的三重四极杆质谱仪联用,对糯高粱样品中的12种农药残留进行了快速筛查,结果表明,本方法灵敏度高,可以满足食品安全国家标准规定的谷物中农药残留最大限量检测要求.     

Development of passive sampler technique for ozone monitoring. Estimation of indoor and outdoor ozone concentration

A passive sampler method has been developed for ozone monitoring. The method involves a badge type passive sampler and is applied to the analysis of ozone exposure as an indoor and outdoor air pollutants. The passive sampler used in this experiment consists of glass fiber filter coated with NaNO(2), Na(2)CO(3) and ethylene glycol, and diffusion filter to remove the wind effects and several spacer effects. The principle component of coating is nitrite ion, which in the presence of ozone is oxidized to nitrate ion on the filter medium and then analyzed by ion chromatography. The results from laboratory and field tests show excellent correlation between the passive method and standard ozone monitoring system, integrated over the same time period. The wind tunnel parameters that were examined show that determination of relative humidity (ranging from 30 to 80%), temperature (ranging from 10 to 20 degrees C) and wind velocity ( ranging from 0.5 to 1.5 m s(-1)) at typical ozone levels (1-40 ppb) do not influence sampler performance. The detection limit attained 0.1 ppb is adequate for the determination of ozone in indoor and outdoor areas. A statistical comparison with a reference method was done in order to demonstrate the validation of the developed method. The accuracy of the proposed method, expressed as a percent relative error, when compared with a standard reference method, is found to be better than about +/-3.5%. The standard errors of the difference was measured in terms of relative standard deviation (R.S.D.) and it was found that the R.S.D. of the passive sampler for O(3) sampler ranged from 2.0 to 6.0%.     

Graphitized carbon black in quartz tubes for the sampling of indoor air nicotine and analysis by microwave thermal desorption-capillary gas chromatography

Nicotine in a smoky indoor air environment can be determined using graphitized carbon black as a solid sorbent in quartz tubes. The temperature stability, high purity, and heat absorption characteristics of the sorbent, as well as the permeability of the quartz tubes to microwaves, enable the thermal desorption by means of microwaves after active sampling. Permeation and dynamic dilution procedures for the generation of nicotine in the vapor phase at low and high concentrations are used to evaluate the performances of the sampler. Tube preparation is described and the microwave desorption temperature is measured. Breakthrough volume is determined to allow sampling at 0.1-1 L/min for definite periods of time. The procedure is tested for the determination of gas and paticulate phase nicotine in sidestream smoke produced in an experimental chamber.     

Development and Calibration of a Portable Air Sampler

This paper describes the development and calibration of a portable air sampler for detecting chemical vapors. The air sampler is equipped with a preconcentrator, a battery operated mini-pump, a three-way valve, capacitive sensors housed in a sensing chamber, and a data acquisition and control circuit board. The preconcentrator is used to adsorb trace level chemicals and to thermally desorb them into the sensing chamber. The air sampler was calibrated using known concentrations of ethylbenzene vapor generated by an Environics gas mixing system. The air sampler was also tested using low concentration toluene and ethanol vapors generated by diffusion based vapor generation device. The concentration factor of the preconcentrator was experimentally determined.     

Polydimethylsiloxane-based permeation passive air sampler. Part II: Effect of temperature and humidity on the calibration constants

Polydimethylsiloxane (PDMS) has low permeability towards water vapour and low energy of activation of permeation towards volatile organic compounds (VOCs) when compared to many other polymers. Suitability of the material for use in permeation-type passive air samplers was tested as it theoretically should reduce uptake rate variations due to temperature changes and eliminate or reduce complications arising from sorbent saturation by water vapour. The calibration constants of a simple autosampler vial-based permeation passive sampler equipped with a PDMS membrane (Waterloo Membrane Sampler^®) were determined for various analytes at different temperatures. From the data, the activation energy of permeation for PDMS towards the analytes was determined. The analytes studied belonged to various classes of compounds with wide ranging polarities, including n-alkanes, aromatic hydrocarbons, esters and alcohols. The results confirmed Arrhenius-type relationship between temperature and calibration constant and the energy of activation of permeation for PDMS ranged from −5 kJ/mole for butylbenzene to −17 kJ/mole for sec-butylacetate. Calibration constants of the samplers towards n-alkanes and aromatic hydrocarbons determined at humidities between 30% and 91% indicated no statistically significant variations in the uptake rate with changes in humidity for 9 of the 11 analytes studied. The results confirmed the suitability of the sampler for deployment in high humidity areas and under varying temperature conditions.