Improved gas chromatographic separation of C6 epoxides

Summary The separation of C₆ epoxides on a fused-silica capillary column coated with Permaphase DMS (dimethylsilicone) was investigated. Retention indices were determined at 50 and 60°C.We demonstrate that this stationary phase provides a better resolving power than OV-101.     

Capillary gas chromatography of C1−C4 alkyl tert-butyl ethers

Summary The separation of C₁–C₄ alkyl tert-butyl ethers with the general formula (CH₃)₃C–O–R (R-alkyl substituent) on fused-silica capillary columns coated with dimethylsilicone and cyanopropylmethylsilicone stationary phases was investigated. Retention indices were determined at two temperatures in order to understand their chromatographic behaviour. The respective standard deviations were 0.3 and 0.5 i.u.     

Automatic headspace gas chromatography of C1–C7 hydrocarbons in sedimentary rocks. Application in Petroleum Geochemistry

Summary The analysis of hydrocarbons (C₁–C₇ molecular range) from the water-saturated pore structure of sedimentary rocks is performed by headspace gas chromatography. Hydrocarbon yields are compared to those of dynamic gas extraction techniques (gas stripping, thermovapourization). Lowest detectable quantity is estimated as 1–10 ppb (w/w) for the C₁–C₅ molecular range. Automation of the method helps to improve its application for routine light-hydrocarbon analysis in rock samples of oil and gas exploration wells. Presented at the 15th International Symposium on Chromatography, Nürnberg, October 1984     

The thermodynamics of mixing C6 and C7 compounds with a bicyclic compound at infinite dilution

The activity coefficients at infinite dilution have been measured at 25°C for cyclohexane, cyclohexene, 1,3-cyclohexadiene, 1,4-cyclohexadiene, benzene, n-hexane, 1-hexene, 1-hexyne, n-heptane, 1-heptene and 1-heptyne in decahydronaphthalene, bicyclohexyl, 1,2,3,4-tetrahydronaphthalene and cyclohexylbenzene. These results, together with previously determined H _m ^E and V _m ^E have been used to calculate the partial molar excess thermodynamic properties of mixing at infinite dilution.     

Characterization of sixty alkenes in a cat-cracked gasoline naphtha by gas chromatography

Summary The alkene-rich petrol fraction from refinery fluid catalytic cracking (FCC) has been characterized by GC and GC-MS. Quantitative proportions and retention data of 52 acyclic and 11 cyclic C₅–C₇ alkenes are given. Relative retentions are reported for methylsilicone and aluminium oxide stationary phases as methylene units (MU). Applications of mass spectra, single-ion GC-MS monitoring and retention data for identifications are demonstrated.     

A column packing for isothermal gas chromatographic analysis of C1−C5 paraffins and monoolefins and dimethyl ether

Summary An analytical GC method was developed which uses a single packed column consisting of three packings in series prepared with the following liquid phases: dimethyl sulfolane, propylene carbonate, and silver nitrate. This system provides satisfactory resolution of mixtures of C₁–C₅ hydrocarbons and dimethyl ether obtained when converting methanol to gasoline. Due to the high capacity of the column it is possible to inject larger sample amounts permitting trace analysis.     

Chromatography of glycols. Regularities in the retention of C3−C6 branched glycols in gas-solid and gas-liquid chromatography

Summary Linear correlation between the major physico-chemical properties of glycols and their relative retention volumes measured by gas-solid (GSC) and gas-liquid (GLC) chromatography is shown. The coefficients of the linear regression equations describing the relationship between the relative retention volumes and the physico-chemical parameters (boiling point, density, etc.) are given. The values of the change in the free energy for the stationary phases studied are given as well as the increments of this change per −CH₂- and CH₃-group. The main factors determining the retention of branched glycols on Polysorb, Tween and poly(ethylene glycol) are shown to be the distance between the hydroxyl groups in their molecules, the presence of alkyl substituents and the type and the number of these substituents.     

A new method to determine reid vapour pressure for stabilized crude oils by gas chromatography

Summary A new rapid method has been developed to determine Reid Vapour Pressure (RVP) for stabilized crude oils by gas chromatography. The quantity of light hydrocarbons dissolved in crude oil was measured directly by gas chromatographic analysis, while the RVP value was computed utilizing a new correlation with this quantity at constant temperature. A variety of crude oils were investigated and the results revealed the accuracy of this method.     

Determination of C1−C4 fatty acids as p-bromophenacyl esters using glass-capillary gas chromatography and electron-capture detection

Summary A method for the determination of low relative molecular mass carboxylic acids (C₁–C₄) in water is reported. The acids are converted to p-bromophenacyl esters prior to a glass-capillary gas chromatographic separation. By utilizing electron-caputre detection the detectability is substantially improved compared to flame-ionization detection. A comparison of three different ways to treat the water samples and to produce the derivatives is made. It is shown that the , p-dibromoacetophenone reagent decomposes to a small extent which limits the utility of the reagent. Nevertheless a detection limit for formic acid of approximately 2.5 mgl^–1 is obtained. The method is applied to the determination of formic and acetic acids in a paper kraft water sample.     

Analysis of hydrocarbons in coal and rock samples by on-line combination of thermodesorption,gas chromatography and mass spectrometry

Summary GC-MS analysis of hydrocarbons, thermally mobilized from rock and coal samples (“thermodesorption”) at 320°C, provides valuable and readily available information of organic geochemical significance. Two oil shale and three coal samples of different rank have been selected for this study. The molecular patterns of compound classes of various saturated and aromatic hydrocarbons are recorded here by employing mass chromatography of selected ions. The method described is of particular importance for the detection of those volatile constituents in coals and sedimentary rocks, which are usually not recovered during elaborate workup procedures (i.e. solvent extraction, liquid chromatography) due to evaporation losses.     

Gas chromatographic retention indices for C6 alkanols on OV-101 and Carbowax 20M capillary columns

Summary Gas chromatographic retention indices for 16 C₆ alkanols measured on capillary columns coated with OV-101 methylsilicone and Carbowax 20M propylethyleneglycol liquid phases at 80° and 90°C were determined. The respective standard deviation values were 0.5 and 0.8 i.u. The correlation between the retention indices measured on non-polar and polar stationary phases and the boiling points of the alkanols was studied.     

Simultaneous thermoanalytical investigations of (C6H5)4AsCl and (C6H5)4PCl under air and argon atmospheres

The thermoanalytical curves of (C₆H₅)₄AsCl (I) and (C₆H₅)₄PCl (II) were generated simultaneously by using a Netzsch simultaneous thermal analyser 409 under static air and dynamic argon atmospheres. The ranges of thermal stability of I and II were found to be 145–310°C and 137–365°C, respectively, and their melting points to be 261 and 278°C. The DTA profiles of I and II differ and can be used for their distinction.     

Determination of mono and disaccharide content of enteral formulations by gas chromatography

Summary A quantitative GC method has been developed which allows determination of mono and disaccharides in enteral formulations. The method is based on the isolation of the mono and disaccharide fraction on a charcoal-celite column and conversion to trimethylsilylated oximes (TMS-oximes). The repeatability of the complete method and recovery were acceptable. In the five commercial samples assayed, maltose was the main sugar (5.24–8.85 gL⁻¹) followed by glucose (1.06–2.41 gL⁻¹) and lactose (0–1.17 gL⁻¹) Low levels of fructose (0–0.18 gL⁻¹) and sucrose (0–0.07 gL⁻¹) were observed and galactose was detected in two of the samples. The presence of maltulose is reported in enteral formulations for the first time. Maltulose formed from maltose during processing, was present in variable amounts (0.12–1.07 gL⁻¹) and could be a useful indicator for enteral formulation classification.     

Discussion of thermodynamic data obtained by adsorption gas chromatography on carbograph 6

Summary Carbograph 6, a new graphitized carbon black with a specific surface area of 203 m² g⁻¹, as measured by BET, both uncoated and coated with up to 12% (w/w) of squalane, a non-polar stationary phase, has been studied by gas chromatographic determination of the enthalpy, entropy, and free energy of adsorption of a series of alkanes (C₂−C₆) and benzene. The data obtained are discussed and compared with those available in the literature for other graphitized carbon blacks. An example of a separation obtaned with Carbograph 6 is reported.     

离子色谱法测定合成气制烯烃产物中的C_1~C_6有机酸

采用离子色谱建立了合成气制烯烃(SGTO)水相产物和油相产物中C1~C6有机酸的测定方法。对分离条件进行了优化,使用标准样品测定了线性范围和工作曲线,考察了方法的精密度和准确度,确定了SGTO油相产物样品的碱洗条件,并对SGTO水相产物和油相产物样品进行了测定。结果表明:C1~C6有机酸的质量浓度在各自配制的质量浓度范围内呈现良好的线性关系,相关系数均大于0.99。标准溶液的回收率测定表明回收率在95.6%~104.3%之间,5次重复测定的相对标准偏差(RSD)在0.4%~3.6%之间,表明该方法具有良好的准确性和精密度。SGTO油相产物中的加标回收率在91.1%~96.8%之间,5次重复测定的RSD为0.7%~2.3%,准确性可以满足实际分析的需要。实际SGTO水相产物和油相产物中C1~C6有机酸的分析结果表明,SGTO水相产物中C2~C4有机酸含量较高,而SGTO油相产物中C4~C6有机酸含量较高。本研究对SGTO反应研究、催化剂制备、工艺优化以及设备材料的选择具有重要意义。     

气相色谱法测定饼干类食品中氯丙醇类化合物

报道了饼干类食品中3-氯-1,2．丙二醇和1,3-二氯-2-丙醇的测定。采用乙醚索氏提取、甲醇萃取净化,再经N,O-双（三甲基硅烷）三氟乙酰胺（BSTFA）衍生,毛细管气相色谱法分离,FID作检测器。方法检出限为0．01mg／kg,回收率在90％～105％,相对标准偏差为2．2％～9．3％,     

Esterification of C2−C16 dicarboxylic acids to n-butyl esters in aqueous solutions for their gas chromatographic analysis

Summary C₂–C₁₆ dicarboxylic acids were esterified in aqueous solution in the presence of sulfuric acid. Esterification in water/n-butanol mixtures with mole ratios between 0.02 and 2.53 can be utilized for the quantitative determination of the dicarboxylic acids by gas chromatography. The presence of water does not interfere at water/n-butanol mole ratios below 0.27. For mole ratios above 0.27 anhydrous sodium sulfate has been used for binding the water. The mole ratio range was 0.25–0.75 for anhydrous sodium sulfate/water, and 0.32–1.3 for sulfuric acid/anhydrous sodium sulfate.     

衍生-气相色谱法测定水产品中的游离甲醛

建立了水产品中游离甲醛残留量的衍生-气相色谱快速检测方法,对衍生剂、抗干扰剂、萃取剂、色谱条件进行了研究.用HP-5 (30 m×0.32 mm i.d.,0.25 μm)毛细管色谱柱,程序升温,γ-ECD检测器,外标法定量.甲醛的检出限为0.05 mg/kg,在0.1～20.0 mg/L范围内,其线性相关系数R2=0.9994,标准偏差为0.041,在0.5、 1.5、 5.0 mg/kg 3个添加水平下回收率为89.6%～102.6%.3个实验室间的RSD为2.7%～4.4%.     

Estimation of C2−C5 hydrocarbons in air by pre-concentration on silica gel at dry ice temperature

Summary A short stainless steel column packed with silica gel is cooled to –78°C and atmospheric hydrocarbons are preconcentrated from 3 I of air on it. Desorption to the analytical column is by heating for 10 min to 200°C. Analysis is by GC on OPN-Poracil C at 27°C. The sorption efficiencies were nearly 100% for most of the light hydrocarbons.