热重分析技术测定二苯并呋喃在活性炭上的吸附相平衡

以吸附动力学为基础,建立了热重分析技术测定难挥发性有机物吸附等温线的方法.通过热重分析实验测定了不同升温速率下二苯并呋喃从Norit RB1和Chemviton BPL活性炭上脱附速率曲线,及对应的脱附峰温度.运用所提出的方法,对二苯并呋喃在Norit RB1和ChemvironBPL活性炭上的Langmuir吸附等温线方程进行了估算.估算结果与静态吸附实验测定结果相比,误差不超过10%.     

环境舱-热脱附-气相色谱/质谱联用法测定软体家具面料中40种挥发性有机物

建立了同时检测软体家具面料中40种挥发性有机物的环境舱-热脱附-气质联用(ETC-ATD-GC/MS)检测方法。以Tenax TA吸附管吸附环境舱内不同面料中释放的挥发性有机物,经热脱附仪加热,将挥发性有机物脱附后随载气进入GC/MS进行定性和定量分析。考察了吸附管脱附温度、脱附时间,冷阱温度等不同参数对挥发性有机物的脱附效率的影响。结果表明,40种挥发性有机物在2~200 ng质量范围内呈良好的线性关系,相关系数在09949~0.9999之间,方法的检测限为0.011~0.277μg/m~3。方法回收率为88.0%~109.9%,相对标准偏差在1.5%~9.5%之间。方法适用于不同软体家具面料中挥发性有机物的定量分析。     

用吹扫捕集-热脱附-气相色谱-质谱法分析生活污水中挥发性有机物

介绍了用于分析生活污水中挥发性有机物的方法,分析物以吹扫捕集法取样,混合吸附剂富集,然后热脱附-气相色谱分析.混合吸附剂是由TenaxGC和活性炭组成,二者体积比为2∶1.对吹扫捕集流速和捕集时间进行了优化,并测定了标准分析物的回收率.利用该法,从生活污水中检出37种挥发性有机物,其中8种列在我国环境优先污染物名单中.     

吸汞载银活性炭纤维和吸汞活性炭纤维的热脱附特性研究

70℃下分别对载银活性炭纤维(载银量14.07%)和活性炭纤维的片状吸附体进行气态汞吸附实验,测定出载银活性炭纤维汞饱和吸附量为192.3 mg/g,活性炭纤维汞饱和吸附量为29.4 mg/g,分别为普通活性炭的48倍～192倍和7倍～29倍.采用热重分析法(TGA)研究了两种吸附剂汞饱和后的热脱附再生特性.结果表明,汞饱和载银活性炭纤维的汞脱附发生在100℃～650℃,在70 min内从50℃升温至650℃,才乏脱附率为94.73%;汞饱和活性炭纤维的汞脱附发生在100℃～230℃,在40 min内从50℃升温至350℃ ,汞脱附率为69.93%.扫描电镜分析发现,载银活性炭纤维因吸附汞而富集的银,经热脱附后变成均匀弥散于纤维表面的亚微米级和纳米级球状银颗粒;吸汞活性炭纤维经热脱附后物理吸附汞基本消失,而氧化汞颗粒反而变多,说明物理吸附的汞易于脱附,氧化汞难以脱附,同时在热脱附过程中存在金属汞向氧化汞的转化.     

吹扫/捕集-热脱附气质联用法对荷叶挥发油成分的对比分析

采用同时蒸馏萃取提取得到荷叶挥发油, 通过吹扫/捕集-热脱附法(P&T-TD)对上述提取物中挥发性成分进行富集, 以气质联用(GC/MS)进行定性检测, 同时与直接进样GC/MS法分析的成分进行比较. 两种方法成功分离分析出有机酸、酯、醛、醇、酚、烷烃、芳香烃、烯烃以及含氮、硫、氧杂原子的化合物等共计84种成分, 其中P&T-TD GC/MS鉴定出63种有机化合物, GC/MS鉴定出41种有机化合物, 有20种成分共同检出. 对比分析表明: P&T-TD GC/MS的吹扫/捕集-热脱附过程能富集各种组分, 相比GC/MS分析, 可以鉴定出微量成分及更多挥发性和半挥发性成分, 在精油等挥发性成分的分析检测中使用优势明显.     

用吹扫捕集—热脱附—气相色谱—质谱法分析生活污水中挥发性 …

介绍了用于分析考活污水中挥发性有机物的,分析物以吹扫捕集法取样,混合吸附剂富集,然后热脱附－气相色谱分析。混合吵附剂是由ＴｅｎａｘＧＣ和活性炭组成,二者体积比为２：１。对吹扫捕集流速和捕集时间进行了优化,并测定了标准分析物的回收率。利用该法,从生活污水中检出３７种挥发性有机物,其中８种列在我国环境优先污染物名单中。     

活性炭吸附–热脱附–气相色谱法测定室内空气中5种挥发性卤代烃

建立活性炭吸附–热脱附–气相色谱法测定室内空气中三氯甲烷、四氯化碳、三氯乙烯、四氯乙烯、三溴甲烷5种挥发性卤代烃含量的方法。选用活性炭为固体吸附剂,热脱附进样,温度为300℃,时间为3 min,捕集阱温度为–5℃,采用配有FID检测器的气相色谱仪检测,以保留时间定性,外标法定量。5种卤代烃的质量浓度在20～500μg/m~3范围内与色谱峰面积有良好的线性关系,相关系数大于0.998,方法检出限为2.7～5.3μg/m~3。样品加标回收率为82.6%～107.5%,测定结果的相对标准偏差为7.3%～13.6%(n=6)。该法具有操作简便,结果准确、可靠等优点,可用于室内空气中挥发性卤代烃的检测。     

固相萃取毛细管气相色谱法测定卷烟滤嘴中7种挥发性羰基化合物

建立了SPE-GC测定卷烟滤嘴中7种挥发性羰基化合物,采用2,4-二硝基苯肼酸性溶液捕集滤嘴中挥发性羰基化合物,捕集液经Waters C18固相萃取小柱纯化和富集,用GC检测.7种羰基化合物检出限分别为0.02、 0.07、 0.04、 0.03、 0.03、 0.02、 0.03 μg/mL;回收率范围在92.0%～99.5%之间;相对标准偏差均小于5%.方法应用于国内5种烤烟型卷烟滤嘴的分析,得到理想结果.     

吹扫/捕集-热脱附气相色谱法研究吸附剂富集水中痕量挥发性有机物的效果

利用自制的吹扫/捕集-热脱附装置,考察了7种单一吸附剂和4种混合吸附剂对水中痕量挥发性有机物的富集,结果证明,Tenax GC和活性炭组成的混合吸附剂使用范围广,回收率明显高于单一吸附剂,吸附剂借助N_2干吹可除去水蒸气.混合吸附剂可望在环境大气和汽提法分析水样中得到广泛的应用.     

热重分析测定脱附活化能分布研究

以脱附过程本征动力学模型为基础,提出了一种采用热重分析技术测定脱附活化能随吸附质分子表面覆盖率分布的方法。该方法通过一条热重分析曲线就可以得到清晰的脱附活化能关于覆盖率的函数表达式。采用所提出的方法,通过不同升温速率下的热重分析实验测定了芴和蒽在活性炭上脱附活化能的线性分布,结果表明覆盖率越高,脱附活化能越低。对芴和蒽,由于覆盖率上升,脱附活化能最大降幅达18.5%和15.1%。     

Determination of highly volatile organic contaminants in water by the closed-loop gaseous stripping technique followed by thermal desorption of the activated carbon filters

Very volatile organic contaminants in water were determined by using closed-loop gaseous stripping combined with thermal desorption from the activated carbon filter into a high-resolution gas chromatograph. The operating parameters for quantitative applications were evaluated. The solvent-free thermal desorption procedure permits the determination of compounds that normally elute under the gas chromatographic solvent peak (e.g., dichloromethane and Freons). Sixteen volatile compounds with boiling points in the range -30 to 120 degrees C were determined with an overall recovery of 12-52%. Qualitative determinations of volatiles from a secondary sewage effluent were in good agreement with the results found by two more established methods.     

Reactivity of Carbon Adsorbents Used to Determine Volatile Organic Compounds in Atmospheric Air

The surface reactivity of carbon adsorbents (carbon molecular sieves and graphitized carbons) used for analysis of volatile organic compounds in atmospheric air was studied using ¹⁸O as a labelling agent. The carbon adsorbent surface activated in a stream of inert gas at 350°C and then exposed to air is very active chemically. Apparently peroxide structures are formed. Owing to this activity the integrity of some analytes, for example dienes and alcohols, among others, is compromised. The active surface can react with the volatile organic compounds analyzed and even initiate free-radical polymerization. The consequences in analytical practice are discussed.     

Hydrodistillation-adsorption method for the isolation of water-soluble, non-soluble and high volatile compounds from plant materials

Proposed method of hydrodistillation–adsorption (HDA) on activated carbon and hydrodistillation (HD) with solvent trap were compared for the isolation of water-soluble, non-soluble and high volatile compounds, such as acids, monoterpenes, isothiocyanates and others from carob (Certonia siliqua L.), rosemary (Rosmarinus officinalis L.) and rocket (Eruca sativa L.). Isolated volatiles were analyzed by GC and GC/MS. The main advantages of HDA method over ubiquitous HD method were higher yields of volatile compounds and their simultaneous separation in three fractions that enabled more detail analyses. This method is particularly suitable for the isolation and analysis of the plant volatiles with high amounts of water-soluble compounds. In distinction from previously published adsorption of remaining volatile compounds from distillation water on activated carbon, this method offers simultaneous hydrodistillation and adsorption in the same apparatus.     

不同材料滤嘴对卷烟主流烟气中挥发性羰基化合物截滤性能的研究

吸烟是引起肺癌及相关疾病的主要原因[1]。挥发性羰基化合物(如甲醛、乙醛、丙醛、丙酮、丙烯醛、巴豆醛、丁酮和丁醛)是卷烟主流烟气中含量较高的一类有害成分,含量从几十到几百微克不等[2-3]。这些挥发性羰基化合物特别是甲醛、丙烯醛及巴豆醛具有纤毛毒性,与氰化氢和氨一起,     

Bio-sniffers for ethanol and acetaldehyde using carbon and Ag/AgCl coated electrodes

Monitoring of ethanol and acetaldehyde in expired gas after drinking is an effective method for assessment of alcohol metabolic function. We have developed bioelectronic gas sensors (bio-sniffers) for convenient measurement of ethanol and acetaldehyde. The bio-sniffers were fabricated using a simple process and inexpensive method. The process consisted of coating carbon and Ag/AgCl on a filter paper using screen-printing, and immobilizing alcohol oxidase and aldehyde dehydrogenase on the carbon electrode. These bio-sniffers showed good response to ethanol and acetaldehyde vapor and were used to sense these vapors in the concentration range 1.0 to 100 ppm and 0.2 to 4.0 ppm, respectively. The calibration ranges cover the alcohol and acetaldehyde concentration in breath air after drinking. The bio-sniffer for acetaldehyde is applicable also to evaluate other aldehydes (i.e. formaldehyde as volatile organic compounds).

     

Trapping of volatile iodine by an activated carbon fiber filter

Model experiments for a simple and effective trapping device of volatile iodine that is generated during radioiodination of biomacromolecules were performed using an activated carbon fiber filter. Over 99.9% of the radioactivity was trapped by the first sheet, when a stream of the volatile radioactive iodine was passed through the layer consisting of several sheets of carbon fiber filter of pore-size 2nm preceded by two or three sheets of urethane foam filter to eliminate the water vapor. Since the carbon fiber filter has very little resistance to the gas flow, the device seems applicable to the small filter chamber for the radioiodination hood.     

Fluorescent and colorimetric detection of acid vapors by using solid-supported rhodamine hydrazides

Rhodamine hydrazide-based chemosensors that can detect volatile acidic gases in solid state have been developed. The rhodamine hydrazide probes adsorbed on filter paper respond fluorescently and colorimetrically only to volatile acidic gases but not to organic bases nor to other volatile organic compounds (VOCs). Diethyl chlorophosphate (DCP), one of model compounds used for the studies of Chemical Warfare Agent (CWA), could also be detected by using this method.     

Method for the collection and analysis of volatile compounds in the breath

A new method is described for the collection and assay of volatile compounds in the breath. Subjects expired into a pump-assisted collecting apparatus in which the breath was drawn through a water trap and then through an adsorptive trap where the volatile compounds were captured on graphitized carbon and molecular sieve. The sample was subsequently eluted from the trap by thermal desorption, concentrated by two-stage cryofocusing, then assayed by gas chromatography with flame ionization and flame photometric detection. Several compounds were regularly observed in the breath of normal human volunteers, including peaks eluting with the same retention times as isoprene, ethanol, acetone, acetaldehyde and carbon disulfide. As a quantitative assay for endogenous isoprene in the breath, the method was sensitive, linear, accurate and reproducible. This method provided a number of advantages: the collection technique was acceptable to volunteers and could be used at sites remote from the laboratory. The automated assay allowed isoprene and several other volatile compounds in the breath to be observed consistently and with improved sensitivity.     

Analysis of odorous compounds in water by isolation by closed-loop stripping with a multichannel silicone rubber trap followed by gas chromatography-mass spectrometry.

An alternative technique for the isolation and concentration of odorous compounds found in potable water is described. The method currently employed by water authorities is closed-loop stripping with the collection of these substances on a small activated carbon filter. The compounds of interest are then extracted from the carbon using a suitable solvent. The authors offer a multichannel silicone rubber trap as an alternative to the carbon filter. The absorbed compounds are thermally desorbed from the trap, directly on to the gas chromatographic column for analysis by GC-MS, thereby eliminating the solvent extraction step required by the carbon filter. The multichannel silicone rubber trap, producing equivalent results, offers a number of advantages over the carbon filter.     

Composite carbon-fluoroplastic surface-layer sorbents for the rapid preconcentration of organic substances from aqueous solutions

The regularities of the dynamic solid-phase extraction of organic substances (exemplified by chloroform, butyl acetate, and diethyl ether) from aqueous solutions on composite surface-layer sorbents, in which a finely dispersed sorption-active carbon material (active carbon or nanocarbon) was supported onto the surface of porous polytetrafluoroethylene, were found. It was demonstrated that the efficiency of the sorbents developed was higher than that of traditional bulk porous sorbents used for the preconcentration of volatile organic substances from aqueous solutions.