ANALYSIS OF VOLATILE CONSTITUENTS OF CHINESE MEDICINAL HERBS BY FLASH DISTILLATION/CAPILLARY GAS CHROMATOGRAPHY/MASS SPECTROMETRY

In present work,the volatile constituents of Curcuma longa L.,A.lancea (Thunb.) DC.,Foeniculum vulgare Mill,and Cinnamomun cassia Presl.have been analyzed by flash distillation/capillary gas chro-matography/mass spectrometry.The results are consistent with those obtained by conventional steam distillation extraction method.The optimum condition of flash distillation has been studied.The experimental results showed that this new technique proved to be a simple,rapid and efficient tool for microanalysis of volatile constituents of Chinese medicinal herbs.

Exergy Analysis and Retrofitting of Natural Gas-based Acetylene Process

This article presents an acetylene production process by partial oxidation/combustion of natural gas. The thermodynamic performance and exergy analysis in the process are investigated using the flow-sheeting program Aspen Plus. The results indicate that the most important destruction of exergy is found to occur in the reactor and water quenching scrubber, amounting to 8.23% and 10.39%, respectively, of the entire system. Based on the results of thermodynamic and exergy analysis, the acetylene reactor has been retrofitted. The improvement ratios of molar 02 to CH4 and molar CO to CN4 are 0.65 and 0.20, respectively. An improvement of the acetylene production system is proposed. Adopting the improvement operation conditions and using oil to realize the reaction heat recovery, the feedstock of natural gas is reduced by 9.88% and the exergy loss in the retrofitting process is decreased by 19.71% compared to the original process.

Thermodynamic Analysis of Alternative Marine Fuels for Marine Gas Turbine Power Plants

The marine shipping industry faces challenges to reduce engine exhaust emissions and greenhouse gases （GHGs） from ships, and in particular, carbon dioxide. International regulatory bodies such as the International Maritime Organization and National Environmental Agencies of many countries have issued rules and regulations to drastically reduce GHG and emissions emanating from marine sources. This study investigates the possibility of using natural gas and hydrogen as alternative fuels to diesel oil for marine gas turbines and uses a mathematical model to assess the effect of these alternative fuels on gas turbine thermodynamic performance. Results show that since natural gas is categorized as a hydrocarbon fuel, the thermodynamic performance of the gas turbine cycle using natural gas was close to that of the diesel case. However, the gas turbine thermal efficiency was found to be slightly lower for natural gas and hydrogen fuels compared to diesel fuel.

Detection of Tocopherol in Oilseed Rape (Brassica napus L.) Using Gas Chromatography with Flame Ionization Detector

The variation among Chinese genotypes of Brassica napus L. for seed tocopherols content and their analysis using gas chromatography has not been comprehensively reported till to date. In the present study, the tocopherol contents of four Chinese genotypes of Brassica napus L., namely, Gaoyou 605, Zhejiang 619, Zheshuang 758, and Zheshuang 72, were evaluated using three modified sample preparation protocols （P1, P2, and P3） for tocopherol extraction. These methods were distinguished as follows. Protocol one （P1） included the evaporation of solvent after extraction without silylation. Protocol two （P2） followed the direct supernatant collection after overnight extraction without drying and silylation. Protocol three （P3） included trimethylsilylation with N,O-bis（trimethylsilyl） trifluoroacetamide. Genotypic comparison of tocopherol and its isoforms revealed that Gaoyou 605 was dominant over the other genotypes with （140.5＋ 10.5）, （316.2＋ 9.2）, and （559.1＋ 24.3） ~tg g-~ of seed meal ct-, 7-, and total （T-） tocopherol, respectively, and a 0.44＋0.04 ^- to 7-tocopherol ratio. The comparison of the sample preparation protocols, on the other hand, suggests that P3 is the most suitable method for the tocopherol extraction from Brassica oilseeds and for the analysis of tocopherols using gas chromatography flame ionization detector （GC-FID）. Trimethylsilylation is the key step differentiating P3 from P1 and P2. Variations detected in tocopherol contents among the Chinese rapeseed （B. napus） genotypes signify the need to quantify a wide range of rapeseed germplasm for seed tocopherol dynamics in short and crop improvement in long.

Some New Techniques of Gas Analysis Developed in RIPP

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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.

Determination of Trihalomethanes in Water Samples Using Headspace Solid-Phase Microextraction Gas Chromatography

The chlorination process is one of the water treatment method used for the disinfection of water. The disinfection by products are trihalomethanes such as chloroform, dichloromethane, dibromochloromethane and bromoform. A headspace solid-phase microextraction method has been developed for determination oftrihalomethanes in water samples. The experimental parameters such as the stirring rate, extraction time, extraction temperature and desorption time were investigated. The linearity, detection limits and percentage recovery were evaluated. The optimum conditions were stirring rate 800 rpm/min, extraction time 6 min, extraction temperature 20 ~C, desorption time 2.5 min and desorption temperature 220 ~C. The detection limits were 0.01 ~g/L and the recoveries were in the range of 86-110 %, The proposed method was successfully applied to determination of THM4 in tap water samples. The THM4 contents were varied depending on the sample sites and the season. The total THM4 contents in cool, summer and rainy season were in the range of 27.58-41.89, 32.06-60.73 and 46.26-69.87 p.g/L, respectively. Confirmation of the detected compounds in water samples were performed by gas chromatograph-mass spectrometer. The mass spectra of the target compounds in water samples is in good agreement with trihalomethanes standard spectra.

Supercritical fluid extraction and gas chromatography analysis of arsenic species from solid matrices

A method in combination with derivatization-supercritical fluid extraction（SFE） and gas chromatography（GC） for the speciation and quantitative determination of dimethylarsinate（DMA）, monomethylarsonate（MMA） and inorganic arsenic in solid matrices was investigated. Thioglycolic acid methyl ester（TGM） and thioglycolic acid ethyl ester（TGE） were evaluated as derivatization reagents. The effects of pressure, temperature, flow rate of supercritical CO_2, extraction time, modifier and microemulsion on the efficiency of extraction were systematically investigated. The procedure was applied to the analysis of real soil and sediment samples. Results showed that TGE was more effective for arsenic speciation as a derivatization reagent. Modifying supercritical CO_2 with methanol can greatly improve the extraction efficiency. Further, the addition of microemulsion containing surfactant Triton X-100 can further enhance recoveries of arsenic species. The optimum extraction conditions were 100 ℃, 30 MPa, 10 min static and 25 min dynamic extraction with 5%（v/v） methanol, and surfactant modified supercritical CO_2. Detection limits in solid matrices were 0.15, 0.3 and 1.2 mg/kg for DMA, MMA and inorganic arsenic,respectively. The method was validated by the recovery data. The resulting method was fast, easy to perform and selective in the extraction and detection of various arsenic species in solid matrices.

Application Progress of Headspace Gas Chromatography in Analytical Chemistry

This paper briefly expounds the basic principle and classification of headspace gas chromatography,summarizes its application in food analysis,environmental analysis and medical analysis,and forecasts the application prospect of headspace gas chromatography in analytical chemistry in the future.

Coupling a Gas Chromatography Unit to an Inductively Coupled Plasma Mass Spectrometer

Although the eminent threat of a terrorist group detonating an improvised nuclear device (IND) in an urban environment is low, it is crucial that countries develop modern nuclear forensic capabilities to expedite response in a post-detonation scenario. In particular, new instruments need to be created to shorten dissolution time, expedite chemical separation, and improve forensic analysis of the nuclear melt glass that is created during the detonation of the device. To expedite this process, an instrument was designed to thermally couple a gas chromatograph (GC) to a time-of-flight inductively coupled plasma time-of-flight mass spectrometer (ICPTOFMS) In order to couple these two instruments, another instrument was designed to provide an isothermal atmosphere between the GC and TOFICPMS to expedite rapid gas separations processes. By using gas separations instead of the current wet chemistry processes, the required separation and analysis time of the melt glass significantly decreases. The new instrument would also provide a more detailed analysis of the elemental and isotopic composition of the melt glass. By completing these tasks simultaneously, this significantly decreases the required time to conduct these separations and improves the elemental and isotopic analysis.

THERMODYNAMIC ANALYSIS OF THE ENANTIOMER RESOLUTION OF TFA-Ala-OMe, TFA-Ala-Ala-OMe, AND TFA-Ala-Ala-Ala-OMe BY GAS CHROMATOGRAPHY ON CHIRASIL-VAL

TFA-Ala-OMe, TFA-Ala-Ala-OMe, and TFA-Ala-Ala-Ala-OMe can be separated into 1, 2, and 4 enantiomeric pairs, respectively, by GC on the chiral stationary phase Chirasil-Val. The selectivity of the chiral stationary phase for the different stereoisomers is controlled by both interaction enthalpy and interaction entropy. The interaction enthalpy is approximately proportional to the number of Ala units. Although the whole molecule is involved in the interaction, the C-terminus plays an important role. The elution order of DDD- and LLL-TFA-Ala-Ala-Ala-OMe is opposite to the order of the enhalpy values, and the ratio of net retention data t’r(DDD)/t’r(LLL) is increased with increasing temperature. By lowering the temperature, peak crossing of the enantiomeric pair has been observed. Below the isoselective temperature Tiso’ the order of elution is ruled by the enthalpy of interaction, above Tiso by the entropy of interaction.

Principal Component Analysis （PCA） on Multivariate Data of Lard Analysis in Cooking Oil

Discrimination of fatty acids （FAs） of lard in used cooking oil is important in halal determination. The aim of this study was to find the information related to the changes FAs of lard when frying in cooking oil. Quantitative analysis of FAs composition extracted from a series of experiments which involving frying cooking oil spiked with lard at three different parameters; concentration of spiked lard, heating temperatures and period of frying. The samples were analyzed using Gas Chromatography （GC） and Principal Components Analysis （PCA） technique. Multivariate data from chromatograms of FAs were standardized and computed using Unscrambler X10 into covariance matrix and eigenvectors correspond to Principal Components （PCs）. Results have shown that the first and second PCs contribute to the FAs mapping which can be visualized by scores and loading plots to discriminate FAs of lard in used cooking oil

Study on the analysis and distribution of dimethylsulfoxide in the Jiaozhou Bay

A chemoreduction-purge-and-trap gas chromatographic method has been developed for the deter-mination of trace dimethylsulfoxide （DMSO） in seawater. In the analysis procedure, DMSO was first reduced to dimethylsufide （DMS） by sodium borohydride and then the produced DMS was analyzed using the purge-and-trap technique coupled with gas chromatographic separation and flame photometric detection. Under the optimum conditions, 97% DMSO was reduced in the standard solution samples with a standard deviation of 5% （n=5）. The detection limit of DMSO was 2.7 pmol of sulfur, corresponding to a concentration of 0.75 nmol/L for a 40 ml sample. This method was applied to determine the dissolved DMSO （DMSOd） and particulate DMSO （DMSOp） con- centrations in the surface seawater of the Jiaozhou Bay, and the results showed that the DMSOd and DMSOp concentrations varied from 16.8 to 921.1 nmol/L （mean：165.2 nmol/L） and from 8.0 to 162.4 nmol/L （mean： 57.7 nmol/L）, respectively. The high concentrations of DMSOp were generally found in productive regions. Consequently, a significant correlation was found between the concentrations of DMSOp and chlorophyll a, suggesting that phytoplankton biomass might play an important role in controlling the distribution of DMSOp in the bay. Moreover, in the study area, the concentrations of DMSOd were significantly correlated with the levels of DMS, implying that the production of DMSOd is mainly via photochemical and biological oxidation of DMS.

Exhaled breath analysis in hepatology: State-of-the-art and perspectives

Liver disease is characterized by breath exhalation of peculiar volatile organic compounds(VOCs).Thanks to the availability of sensitive technologies for breath analysis,this empiric approach has recently gained increasing attention in the context of hepatology,following the good results obtained in other fields of medicine.After the first studies that led to the identification of selected VOCs for pathophysiological purposes,subsequent research has progressively turned towards the comprehensive assessment of exhaled breath for potential clinical application.Specific VOC patterns were found to discriminate subjects with liver cirrhosis,to rate disease severity,and,eventually,to forecast adverse clinical outcomes even beyond existing scores.Preliminary results suggest that breath analysis could be useful also for detecting and staging hepatic encephalopathy and for predicting steatohepatitis in patients with nonalcoholic fatty liver disease.However,clinical translation is still hampered by a number of methodological limitations,including the lack of standardization and the consequent poor comparability between studies and the absence of external validation of obtained results.Given the low-cost and easy execution at bedside of the new technologies(e-nose),larger and well-structured studies are expected in order to provide the adequate level of evidence to support VOC analysis in clinical practice.

Gas Chromatography–Mass Spectrometry for Quantitative and Qualitative Analysis of Essential Oil from Curcuma wenyujin Rhizomes

Objectives:A rapid and sensitive gas chromatography–mass spectrometry(GC–MS)method for quantitative and qualitative analysis of essential oil from Curcuma wenyujin rhizomes was established.Methods:The essential oil of C.wenyujin rhizomes was extracted by supercritical CO2 extraction(SFE).Six main bioactive compounds(eucalyptol,β-elemene,curzerene,germacrone,curdione,and curcumol)were analyzed in selected ion monitoring mode(SIM).Results:Curzerene is not originally present in C.wenyujin rhizomes,but is a product of the transformation of furanodiene at high temperature.The six target components demonstrated good linearity(R2>0.9979)over a relatively wide concentration range.The interday and intraday variations had relative standard deviation values less than 5%and the average recovery ranged from 96.95%to 100.04%.The limit of quantitation ranged from 0.032 to 0.235μg/mL.The developed method was successfully used to analyze the six compounds in 17 samples collected from different origins.Significant variation was observed for the concentrations of the six compounds.In addition,51 constituents were identified in C.wenyujin rhizome essential oil,consisting of 87.66%of the total essential oil,including curdione,curzerene,dehydrocurdione,germacrone,1,4-bis(2-benzimidazoyl)benzene,neocurdione,curcumenone,andβ-elemene.Conclusions:The proposed method will be useful in the quality control of C.wenyujin rhizome essential oil production.

Simultaneous Determination of Halogen Compounds and Sulfur Oxides in Flue Gas by Ion Chromatography

Ion chromatography （IC） is a suitable analytical method for the determination of anions. As analytical methods for the halogen compounds in flue gas, those of bromine compound, fluorine compound, chlorine （Cl2） and hydrogen chloride （HCI） are listed in JIS. However, IC has not been adopted in JIS except for HCI and C12. Because the carbon dioxide in flue gas is absorbed in a 0.1 M sodium hydroxide solution as an absorber, it is interfered with the measurement of F^- and Cl^- ions. This paper describes the development of the pretreatment equipment for the flue gas analysis by IC, and its applications to real flue gas analysis. The F^-, Cl^-, Br^- and SO4^2- in the absorbing solution can be clearly separated by IC using the pretreatment equipment. The halogen compounds and sulfur oxides in flue gas can be simultaneously determined by IC.

Structure and Vibrational Spectroscopy of 2-Methylallyl Alcohol

The intramolecular O−H…πhydrogen bond has garnered significant research interest in recent decades.In this work,we utilized the infrared(IR)-vacuum-ultraviolet(VUV)nonresonant ionization detected IR spectroscopy(NRID-IR)method to study the molecular structure of neutral and cationic 2-methylallyl alcohol(MAA,CH_(2)=C(CH_(3))−CH_(2)−OH).Density functional theory calculations revealed five stable neutral and three stable cationic MAA conformers,respectively.Two neutral MAA conformers are expected to have an O−H…πintramolecular hydrogen bond interaction,based on the structural characterization that the OH group is directed toward the C=C double bond.The IR spectra of both neutral(2700−3700 cm^(−1))and cationic MAA(2500−7200 cm^(−1))were measured,and the anharmonic IR spectra were calculated at the B3LYP-D3(BJ)/def2-TZVPP level.The OH stretching vibration frequency of neutral MAA was observed at 3656 cm−1,slightly lower than those of methanol and ethanol.In contrast,the OH stretching vibration of cationic MAA was red-shifted by about 140 cm^(−1)compared to neutral MAA.The interaction region indicator and natural bond orbital analysis suggest that the O−H…πinteraction in neutral MAA is weak,and may not play a major role in stabilizing the neutral MAA.

Study on Fine Structure of Gas Atomized LaNi_5-based Alloys

The fine structure of hydrogen storage alloy powders MiNi4.3-xCoxMr0.4AI0.3(x=0.75, 0.45, 0.10; Ml: La-rich misch metal) prepared by rapidly solidifying gas atomization was investigated using a Rietveld analysis method. Two sets of CaCu5-type crystal constants were observed in the studied alloys and one set was larger than the other. With decreasing powder radius the solidification rate of powder increased, and so did the percentage of a particle part with larger crystal constants. The reason why there were two sets of crystal constants might be the difference of solidification rate between the outside and inside of a particle.

Efficient Separation of Ar and Kr from Environmental Samples for Trace Radioactive Noble Gas Detection

Radioactive noble-gas isotopes, SSKr （half-life tl/2=10.8 y）, 39Ar （tl/2=269 y）, and SlKr （t1/2-229,000 y）, are ideal tracers and can be detected by atom trap trace analysis （ATTA）, a laser-based technique, from environmental samples like air and groundwater. Prior to ATTA measurements, it is necessary to efficiently extract krypton and argon gases from samples. Using a combination of cryogenic distillation, titanium chemical reaction and gas chromatography, we demonstrate that we can recover both krypton and argon gases from 1-10 L ＂air-like＂ samples with yields in excess of 90% and 98%, respectively, which meet well the requirements for ATTA measurements. A group of testing samples are analyzed to verify the performance of the system, including two groundwater samples obtained from north China plain.

Developing an authentication approach using SPME-GC-IRMS based on compound-specific δ^(13)C analysis of six typical volatiles in wine

An analytical method using gas chromatography isotope ratio mass spectrometry(GC-IRMS)combined with solid phase micro-extraction(SPME)was developed to measure the 613C values of six typical volatiles commonly occurring in wine(isoamyl acetate,2-octanone,limonene,2-phenylethanol,ethyl octanoate and ethyl decanoate)for the first time.SPME selected with a divinylbenzene/carboxen/polydimethylsiloxane fiber was combined with the GC-IRMS for pretreatment optimization.The optimized SPME parameters of extraction time,extraction temperature and salt concentration were 40 min,40℃ and 10%,respectively.The 613C values measured by SPME-GC-IRMS were in good agreement with those measured via elemental analyzer(EA)-IRMS and GC-IRMS.The differences range from 0.02‰to 0.44‰ with EA-IRMS and from 0 to 0.28‰ with GC-IRMS,indicating the high accuracy of the method.This newly established method measured the precision within 0.30‰ and was successfully validated to discriminate imported real wine samples with identical label but amazing price differences from different importers.