Determination of 7 Indictor Polychlorinated Biphenyls (PCBs) Residues in Porphyra by Ultrasonic Extraction and Gas Chromatography (GC)

A method was developed for determination of 7 indictors the polychlorinated biphenyls (PCBs) residues in porphyra by gas chromatography (GC) with electron capture detector (ECD). The PCBs were extracted with hexane/methylene chloride (1:1, v/v) by ultrasonic extraction and the samples were cleaned up by concentrated sulfuric acid and Alumina-N solid phase extraction cartridge. The analytes were quantified by an internal standard method. Under optimal experimental conditions, good linearity was observed in the range of 5 - 200 ng/mL and the correlation coefficients were 0.9994 - 0.9998. The limit of quantitation (LOQ) for target analytes ranged from 6.0 to 10.0 μg/kg. At the spiked levels of 10, 50, 100 μg/kg, the average recoveries ranged from 90.9% to 102% with the relative standard deviations 2.12% - 6.32%. The result showed that the proposed method was rapid, and could be used for the determination of the PCBs in porphyra.

广防己挥发油的GC-MS指纹图谱研究

防己药材主要分粉防己和木防己两类,木防己包括广防己和汉中防己.广防己为马兜铃科植物广防己Aristolochia fangchi Y.C.WuexL.D.Chou.et S.M.Hwang的干燥根[1],习称"木防己"、"水防己",主产于广东、广西,具有祛风止痛、清热利水之功效[2].……

GC-MS Analysis of Essential oil and n-Hexane Extract from Moso Bamboo

[Objective] This study aimed to analyze the chemical composition and yield of essential oil and n-hexane extract from moso bamboo to find active compounds with potential value. [Method] Essential oil and n-hexane extract were respectively extracted from moso bamboo of four different ages by using hydrodistillation and ultrasonic-assisted extraction with n-hexane, and analyzed with gas chromatography/mass spectrometry （GC/MS）. [Result] The results show that cedrol （46.39%） is the first principal volatile component in essential oil of the middle stem of 7-year old moso bamboo; dibutyl phthalate （59.46%） is the first principal volatile component in n-hexane extract of the middle stem of 3-year old moso bamboo; yield of n-hexane extract is higher than that of essential oil from moso bamboo. [Conclusion] Cedrol is an active compound with potential value.

自动固相微萃取(SPM E)GC-MS、GC-MS-MS法检测环境水中有机磷杀虫剂的研究

固相微萃取(solid-phase microextraction,SPME)是20世纪90年代发展起来的一种样品前处理技术,与传统的液-液提取、液-固提取相比,SPME更适用于提取、浓缩液态或气态的挥发性和半挥发性物质,SPME技术可将采样、萃取、浓缩和样本引入集中于一个步骤完成,尤其随着自动SPME与GC-MS等联用技术的日益完善,使SPME技术优点得到更充分的发挥.……

A GC×GC-ToFMS Investigation of the Unresolved Complex Mixture and Associated Biomarkers in Biodegraded Petroleum

Heavy biodegraded crude oils have larger numbers of coeluting compounds than nonbiodegraded oils, and they are typically not resolved with conventional gas chromatography（GC）. This unresolved complex mixture（UCM） has been investigated using comprehensive two-dimensional gas chromatography–time-of-flight mass spectrometry（GC×GC-To FMS） within a set of biodegraded petroleums derived from distinct sedimentary basins, including northwestern Sichuan（Neoproterozoic, marine）, Tarim（Early Paleozoic, marine）, Bohai Bay（Eocene, saline/brackish） and Pearl River Mouth（Eocene, freshwater）. In general, the hydrocarbons that constitute the UCM in petroleum saturate fractions can be classified into three catalogues based on the distributions of resolved compounds on two dimensional chromatograms. Group 1 is composed mainly of normal and branched alkanes, isoprenoid alkanes and monocyclic alkanes; Group 2 comprises primarily terpanes ranging from two to five rings, and Group 3 is dominated by monoaromatic hydrocarbons such as tetralins and monoaromatic steranes. In addition, the UCM is source dependent and varies between oil populations. i.e., the UCM of petroleum derived from Precambrian and Early Paleozoic marine, Eocene saline/brackish and freshwater source rocks is specifically rich in higher homologues of A-norsteranes, series of 1,1,3-trimethyl-2-alkylcyclohexanes（carotenoid-derived alkanes）, and tetralin and indane compounds, respectively.

Determining organic compounds in coking wastewater by SPME-GC /MS

The solid-phase microextraction （SPME） combined with gas chromatography/mass spectrometry （GC/MS） was used to determine and analyze organic pollutants in coking wastewater. Based on the fact that the main compounds in the wastewater were organics, some key parameters of the SPME were optimized. The method has good linearity （ its correlation coefficients 〉 0.99） in the range determined,its relative standard deviations （RSD） are less than 15%, and its recovery is from 87.9% to 128.1% with the lowest quantification limit of 5 ~g/L. This method has been used to measure 15 organic pollutants in wastewater from a certain coking plant. The results show that compared with the conventional method,it can save an hour in pretreatment time. It is a fast, low-cost, accurate, simple and efficient analytical method indeed.

Analysis on Volatile Components of Flowers and Leaves of Thymus mongolicus by SPME-GC/MS

[Objectives] To analyze volatile components of flowers and leaves of Thymus mongolicus. [Methods]Volatile components of collected T. mongolicus flower and leaves were separated by headspace solid-phase microextraction( SPME) and identified by gas chromatography/mass spectrometry( GC/MS) and normallized by peak area. [Results] A total of 24 and 14 compounds were identified from flowers and leaves of T. mongolicus in the total ion chromatogram,accounting for 99. 573% and 97. 187% of the total peak area,respectively. Main components of flowers and leaves of T. mongolicus include phenols and terpenes,and thymol accounts for 35. 38% and 49. 13% of flowers and leaves of T. mongolicus,respectively. [Conclusions] SPME-GC/MS can be applied in analyzing volatile components of flowers and leaves of T. mongolicus,to provide basis for further development and utilization of T. mongolicus.

Effective and inexpensive gas chromatography method for detection of trace level SO_2 in H_2 fuel

Gas chromatography （GC） analysis of sulfer dioxide is challenging because SO2 is a highly mobile and chemically active molecule. For the conventional GC method with flame photometric detector （FPD） and direct-injection, it is often ineffective particularly when the SO2 level is as low as on the trace level. In this paper, a modified GC system integrated with an adsorption-desorption device was developed to detect the trace SO2 impurity in H2 fuel. Adsorbent GDX-502 is used in the adsorber to adsorb/collect SO2 from the sample gas and desorb/release it in a concentrated flow so that the conventional GC at downstream could detect it with an acceptable accuracy.

Using GC to determinate polychlorinated biphenyls in soil after pretreated with microwave-assisted alkaline degradation method

A new and simple microwave-assisted alkaline degradation （MAAD） method for the elimination of organoehlorine-pesticide interference on the determination of polychlorinated biphenyls （PCBs） in soil by GC is presented. Under the optimal conditions, the interference of α- HCH, β- HCH, γ -HCH,δ -HCH, o. p＇ - DDT, p. p＇ - DDD and p. p＇ - DDT could be eliminated completely, and p. p＇ - DDE, Aldrin and Dieldrin could be partially eliminated; however, Dieldrin could be completely eliminated by using concentrated sulphurie acid. The method was evaluated by analyzing the spiked-soil sample. The mean recovery obtained was 84. 1% and the Relative Standard Deviation （RSD） was 2. 7%. Experimental results also indicate that the degradation of the interference and the extraction of the target analytes, PCBs, could be carried out simuhaneously. Compared with the traditional methods, the MAAD method is a rapid, efficient and solvent-saving method,

阀切换技术在大气样品中六氟化硫快速分析中的应用

建立了双柱阀切换技术分析大气样品中的SF6含量的气相色谱-电子捕获检测器（GC-ECD）检测方法。采用规格为3.2mm×1m的5A分子筛（40-60目）柱为预柱,规格为3.2mm×0.5m的5A分子筛（60-80目）柱为分析柱。在所用实验条件下,平均峰高响应为1.08×10^-14mL/μV,SF6单位体积进样量的色谱峰高的相对标准偏差为2.2%,SF6的最低检测限为6.03×10^-13mL（3倍基线噪声）。采用该方法分析大气中SF6的含量,样品分析时间为1.2min,于12min内完成11个空气样品的分析,SF6含量的相对标准偏差2.1%。

程序升温汽化大体积进样气相色谱法同时测定空气中的甲醛及其他10种羰基污染物（英文）

Long-term indoor-air limit for formaldehyde stipulated by the European Commission is 1 μg/m3,while the World Health Organization has set a threshold of 100 μg/m3 that should not be exceeded for more than 30 min. To date,however,only a few analytical techniques have been developed that can be used to detect formaldehyde at these very restrictive limits. Thus,there is a need to develop for comprehensive methods for analyzing airborne formaldehyde and other carbonyl pollutants in the ambient environment. The aim of this study is to develop a highly sensitive online automated preconcentration gas chromatographic method using large-volume injection with a programmed temperature vaporization injector for the analysis of airborne formaldehyde and ten other carbonyl compounds. The influence of several parameters,such as the maximum volume injected,programmed temperature vaporization transfer time and temperature,carrier gas flow rate,and type of packing material was investigated. After optimization,highly satisfactory results in terms of the absolute and methodological detection limits were achieved,i. e. as low as the μg/m3 level for all the carbonyl pollutants studied. A commercially available sampler,originally designed for active sampling,was evaluated as a passive sampling device;this optimized technique was applied to monitor the concentrations of carbonyl pollutants in the indoor air of ten public buildings in Florence. The strength of this methodology lies both in the low detection limits reached in the simultaneous analysis of a wide group of 2,4-dinitrophenylhydrazine derivatives,and the potential adaptability of this method to other gas chromatographic applications to achieve lower sensitivity.

Capillary gas chromatographic determination of dimethachlon residues in fresh tobacco leaves and cut-tobacco

Simple procedures for extraction and chromatographic determination of dimethachlon residues in fresh tobacco leaves and cut-tobacco are described.The determination was carried out by capillary gas chromatography(GC) with electron capture detection(ECD) and confirmed by GC-MS.The mean recoveries and relative standard deviation(RSD) were 93.2%～112.9% and 3.5%～6.7%,respectively at levels ranging from 0.01 to 0.1 mg/kg.The limit of determination was 0.001 mg/kg.Tobacco samples in routine check were successfully analyzed using the proposed method.

气相色谱法探究聚醚醚酮的热降解及热氧化降解（英文）

Poly(ether ether ketone)(PEEK)was synthesized via polycondensation of hydroquinone with 4,4′-difluorobenzophenone at 320℃for 5 h.Thermal and thermo-oxidative degradation of PEEK was studied over a wide range of temperatures.In an inert medium,decomposition of the polymer occurred in one stage,with the formation of a coke residue accounting for approximately 50%of the original polymer mass.In air,the mass loss curve exhibited two distinct stages.The first stage involved breakdown of the main polymer chain,the speed of which indicated a radical chain failure mechanism.In the second stage,the rate of mass loss clearly decreased,indicating a transition from the radical chain failure mechanism to simple combustion reactions(wherein the polymer combusted completely).To further investigate the nature of the processes occurring during the pyrolysis of PEEK,the investigations were carried out using gas chromatograph under isothermal conditions.It was concluded that during thermal degradation,the decomposition of the polymer starts with the rupture of ketone and ether bonds and proceeds to destruction of the benzene ring at higher temperatures,which is accompanied by the formation of H2O and CH4.Above 500℃,the polymer degradation further involved thermohydrolysis.The thermo-oxidation of PEEK,which was accompanied mainly by the formation ofH2,was noticeable beginning at 325℃.The total yield of the latter indicated oxidation of fragments of the benzene ring.

气相色谱分析中是否一定要用质谱检测器? (英文)

The detector,as well as being an essential supporting device for the gas chromatography(GC) has also played a critical role in the development of the technique as a whole.The mass spectrometer(MS) is still the commonly praised detector as before.In fact,the information of fragmentation patterns is seldom used in practice,and the GC-MS instrument is even more expensive.For today's analytical problems,it seems that element specific detectors can and should be used for many applications rather than GC-MS.

Determination of Xenon in Air by a Pulse-discharge Helium Ionization Detector

A pulse-discharge helium ionization detector（Valco, PD-D3-I） was used to measure xenon concentration in air. The dependences of the detector relative response on various gas chromatograph parameters were investigated. Based on the well prepared gas connections for the detector system and optimized gas chromatography（GC） working conditions, the atmospheric xenon concentration could be measured by the cheap GC method with a detection level of 0.7×10-9（parts by volume）. Moreover, the xenon concentration in the ground level air around our laboratory was measured with the result of 0.085×10-6（parts by volume） and RSD of 0.91%.

Test on oxygen and benzene contents in gasoline by mid-infrared spectroscopy

This paper aims at testing oxygen and benzene contents in gasoline by mid-infrared spectroscopy.The experimental results prove that infrared spectroscopy(IR)is reliable.Compared with gas chromatography(GC)technology,this paper draws a conclusion that IR has several advantages,including rapid analysis,excellent repeatability and low analysis cost.

Processing impact on volatile compounds profile in higholeic and normal peanut oil

With the improvement of living quality, high-oleic peanuts have drawn people’s attention. Increasing oleic acid content of peanut oil should be desired for improving shelf life and potential health benefits. The flavor is among the most important quality attributes for commercial acceptance of peanuts products. The volatile components of high-oleic pea-nuts oil and normal-oleic lines were compared in this research. First, volatile components of peanut oils were analyzed and identified by solid-phase microextraction/gas chroma- tography/mass spectrometry （SPME/GC/MS）. Then principal components analysis （PCA） was used to identify principal volatile components in peanut oils of different cultivars fo卜 lowing three different processing methods, including roasting, boiling and roasting, and roasting by microwave-assisted. The results showed that there were obvious differences of the volatile components between high-oleic and normal peanut oils. Among different pro-cessing method of peanuts, there was no clear separation on volatile components observed between roasting and boiling and roasting by microwave-assisted. Moreover, the same genotype had the similar flavor characteristic. Different processing methods had no signifi-cant effect on volatile components in peanut oils.

Chemical composition and antimicrobial activity of the essential oil of Cacalia tangutica (Maxim.) Hand.-Mazz

Essential oil of the subterranean part of Cacalia tangutica(Maxim.)Hand.-Mazz was analyzed by gas chromatography(GC)-mass spectrum(MS)technique in two different capillary columns of different polarities.Thirty-one components were identified in the oil and the main compounds were a-zingiberene(13.49%),germacrene D(10.76%),α-pinene(8.54%),caryophyllene(Z-)(6.36%),linalool(6.16%),β-myrcene(4.89%),β-ocimene(Z-)(4.40%)and ocimenone(Z-)(3.58%).The antimicrobial activity of the oil was evaluated against 2 fungi and 12 bacteria including 6 clinically isolated strains using the agar disc diffusion and broth microdilution methods.The results show that the oil presented a broad antimicrobial spectrum and had better antimicrobial activity against yeast and gram-positive bacteria.The minimum inhibitory concentration values were 0.16–5.00 g/L and minimum bactericidal concentration values were 0.16–5.00 g/L.