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131.
Silicones have innumerable applications in many areas of life. Polydimethylsiloxane (PDMS), which belongs to the class of silicones, has been extensively used in the field of analytical chemistry owing to its favourable physicochemical properties. The use of PDMS in analytical chemistry gained importance with its application as a stationary phase in gas chromatographic separations. Since then it has been used in many sample preparation techniques such as solid phase microextraction (SPME), stir bar sorptive extraction (SBSE), thin-film extraction, permeation passive sampling, etc. Further, it is gaining importance in the manufacturing of lab-on-a-chip devices, which have revolutionized bio-analysis. Applications of devices containing PDMS and used in the field of analytical chemistry are reviewed in this paper. 相似文献
132.
采用顶空-气相色谱法测定了食品用软质塑料包装材料中具有代表的10种挥发性有机物(VOC′s),包括甲苯、乙酸乙酯、2,4-戊二酮、2-乙基-1-己醇、1-壬醛、癸烷醛、十二烷醛、癸烷、正辛烷及十二烷,并用基体匹配法抵消了样品本身的基体干扰。从待分析样品(包装膜)裁取约100cm2大小片样置于真空烘箱中,于90℃烘24h,此片试样即可作为空白基质,再加入一定量的上述VOC标准溶液制备校准曲线。另取同一样品一片,剪碎后移入顶空瓶中,立即盖紧,在100℃平衡30min。方法中用HP-INNOWAX色谱柱在20℃~220℃温度区间程序升温,对各VOC进行分离,采用火焰离子化检测器检测。测得10种VOC′s的检出限(3S/N)在0.2~2.0μg.dm-2之间。另测得平均回收率及相对标准偏差(n=6)分别在82.5%~97.6%和0.9%~14.0%之间。 相似文献
133.
Influencing atmospheric OH radical budget and tropospheric ozone production,ambient formaldehyde(HCHO) is one of the key oxygenated volatile organic compounds(OVOCs).We present the variations on formaldehyde column densities in summertime in Beijing retrieved from ozone monitoring instrument(OMI) between 2005 and 2011.Satellite columns of HCHO correlated well with available ground-based measurements despite some noticeable differences.The orthogonal distance regression(ODR) method was used to estimate the ratio between satellite columns and ground-level concentrations,whereas ordinary least squares(OLS) method was used to fit the trend of ambient formaldehyde.The formaldehyde concentrations derived from HCHO columns were in the range of 7-12 ppbv and steadily increased at an approximate rate of 0.64 ppbv/yr(7.8%at 2005 level) with an uncertainty of 51%.VOC reactivity quantified by means of OH loss rates showed increasing contribution from formaldehyde and acetaldehyde, rising from 35%in 2005 to 40%in 2010,and decreasing contribution from anthropogenic VOCs,dropping from 49%in 2005 to 40%in 2010.More attention should be paid to understanding the net feedback of increasing formaldehyde to ozone formation potential. 相似文献
134.
Determination of complex mixtures of volatile organic compounds in ambient air: canister methodology
Canister methodology is applicable to 150 polar and nonpolar VOCs found in ambient air from parts-per-billion by volume (ppbv)
to parts-per-million (ppmv) levels, and has been validated at parts-per-trillion (pptv) levels for a subset of these analytes.
This article is a detailed review of techniques related to the collection of volatile organic compounds (VOCs) in evacuated
Summa and fused-silica-lined canisters, and their analysis by gas chromatography/mass spectrometry (GC/MS). Emphasis is placed
on canister cleaning, VOC stability in canisters, sample dilution, water management, and VOC cryogenic and sorbent preconcentration
methods. A wide range of VOC preconcentration and water management methods are identified from the literature, and their relative
merits and disadvantages are discussed. Examples of difficulties that commonly arise when processing canister samples are
illustrated, and solutions to these problems are provided. 相似文献
135.
NIAEI Aligholi SALARI Dariush HOSSEINI Seyed Ali KHATAMIAN Masumeh JODAEL Azadeh 《中国化学》2009,27(3):483-488
Gas phase catalytic combustion of ethyl acetate, as one of volatile organic compounds (VOC), was studied on nanostructure ZSM-5, HZSM-5 and Co-ZSM-5 with different cobalt loadings. Nanostructure of ZSM-5 was determined by XRD, SEM and TEM. Catalytic studies were carried out under atmospheric pressure in a fixed bed reactor. Results showed that the Co-ZSM-5 catalysts had better activity than others and at temperatures below 350 ℃, amount of Co loading was more effective on catalytic activity. The order of conversion of ethyl acetate over different Co loading is as follows: Co-ZSM-5 (0.75 wt%)<Co-ZSM-5 (1.5 wt%)<Co-ZSM-5 (15 wt%)<Co-ZSM-5 (2.8 wt%). Besides the higher the inlet concentration of ethyl acetate, the lower the conversion yield, and oxygen concentration in catalytic oxidation conditions has not so large influence on conversion. Furthermore, the presence of water vapor in inlet gaseous feed has an inhibitive effect on ethyl acetate conversion and at the temperatures above 400˚C, the effect decreases. 相似文献
136.
Maxinne Denis Damien Le Borgne Rodolphe Sonnier Sylvain Caillol Cdric Totee Claire Negrell 《Molecules (Basel, Switzerland)》2022,27(15)
Novel phosphorylated cardanol molecules based on phosphonate (PO3CR) and phosphate (PO4CR) functions were synthetized. Those molecules have two main actions which are described in this article: the reduction in volatile organic compounds (VOC) and the development of flame retardant (FR) properties conferred on alkyd resins used as coatings for wood specimen. Phosphorylated cardanol compounds have been successfully grafted by covalent bonds to alkyd resins thanks to an auto-oxidative reaction. The impact of the introduction of PO3CR and PO4CR on the film properties such as drying time and flexibility has been studied and the thermal and flame retardant properties through differential scanning calorimeter, thermogravimetric analysis and pyrolysis-combustion flow calorimeter. These studies underscored an increase in the thermal stability and FR properties of the alkyd resins. In the cone calorimeter test, the lowest pHRR was obtained with 3 wt% P of phosphate-cardanol and exhibited a value of 170 KW.m−2, which represented a decrease of almost 46% compared to the POxCR-free alkyd resins. Moreover, a difference in the mode of action between phosphonate and phosphate compounds has been highlighted. The most effective coating which combined excellent FR properties and good coating properties has been obtained with 2 wt% P of phosphate-cardanol. Indeed, the film properties were closed to the POxCR-free alkyd resin and the pHRR decreased by 41% compared to the reference alkyd resin. 相似文献