Automated in situ analysis of volatile sulfur gases using a Sulfur Gas Analyser (SUGAR) based on cryogenic trapping and gas-chromatographic separation

Based on the technique of cryogenic trapping, gas-chromatographic separation, and flame-photometric detection, we designed an instrument for the analysis of reduced sulfur compounds. The fully automated Sulfur Gas Analyser (SUGAR) consists of a dual sampling system, an electrically cooled cryotrap, and a newly devised small gas chromatograph, which is integrated mechanically and in terms of system control. The system incorporates microprocessor control and provides significant ease of operation. All operational parameters necessary for a complete sampling audit trail are logged on non-volatile memory. SUGAR achieves adequate sensitivity for measuring reduced sulfur gases at typical atmospheric concentrations. Applications under laboratory conditions and in the field demonstrate the versatility of the automated system. Field deployment proved the capability of continuous operation over a period of several weeks. The potential for further improvements of sensitivity and portability by use of different sulfur specific GC detectors is discussed.     

Noncryogenic FSOT column separation of sulfur-containing gases

Fused silica open tubular (FSOT) capillary column GC separations of low molecular weight, reactive sulfur-containing gases (S-gases) are significant improvements over packed column separations in terms of resolution, detection limits, and conditioning effects. Nevertheless, some of the problems with current FSOT capillary systems include matrix Injection incompatibilities; detector dead volumes; the necessity for cryogenic initial oven temperatures to separate CO₂, H₂S, COS, and SO₂; and relatively long analysis times to separate later, closely eluting compounds. A noncryogenic FSOT GC-FPD system that either reduces or eliminates these problems is reported. Baseline separation of seven common S-gases (H₂S-DMDS) is achieved in less than 5 min with ambient initial oven temperatures via this system, which is a combination of (1) a cryogenic sample concentration/injection design that is flow compatible with a wide-bore FSOT column; (2) a combined DB-1/DB-WAX thick phase, wide-bore FSOT column for greater capacity, retention, and tuned selectivity; and (3) a reduced dead volume FPD to minimize peak width and tailing.     

Gas chromatographic separation of anaesthetic gases on a single column

Summary Gas chromatography has been employed in the separation of mixtures of air, carbon dioxide, nitrous oxide and a volatile anaesthetic (halothane, isoflurane or enflurane) on a single Chromosorb 101 column by temperature programming from room temperature. Calibration over the required range for the analysis of exhaled air, demonstrated good linearity with a repeatability for test mixtures of about 1%.     

Synthesis of silica adsorbent and its selective separation for flavone

One kind of built-in silica adsorbent, which has high adsorption selectivity to rutin, was synthesized using molecular imprinting technology by the following steps: synthesis of precursor from the reaction between water soluble rutin (as template molecule) and the functional monomer chloropropyltriethoxysilane, co-hydrolysis of the precursor and tetraethoxysilane (TEOS), sol-gel aging process, and removal of template molecules. The results of adsorption experiment show that this adsorbent has a high adsorption capacity for rutin, and good adsorption selectivity towards rutin even under the interference of a flavone with a similar structure. TEM photos suggest that nanocaves corresponding to rutin were formed inside the adsorbent while FTIR spectra indicate that new bond was generated during the recognition process. __________ Translated from Journal of Tianjin University, 2007, 40(4): 411–415 [译自: 天津大学学报]     

Adsorption of carbon dioxide on microporous carbon adsorbent PAU-10

Carbon dioxide adsorption on the microporous carbon adsorbent PAU-10 within the 177.8—423 K temperature and 0.1—5.13·10⁶ Pa pressure intervals was studied. The isosteres of absolute adsorption are well approximated by straight lines, which do not change their slope on going to temperatures higher than the critical temperature of CO₂. An increase in the differential molar isosteric heat of adsorption (q _st) at 0 < a < 1 mmol g^–1 is explained by the influence of the endothermic effect of adsorption expansion of the adsorbent. In the region of high pressures and nonideal gas phase, q _st is temperature-dependent.     

Solubility of some carrier gases in stationary liquid phases used in gas-liquid chromatography

A simple gas chromatographic technique for the determination of the solubility of gases in low-volatile liquids was proposed. The procedure is based on the introduction of a certain volume of the liquid saturated with the gas at atmospheric pressure into a gas chromatograph. The solubility of carrier gases (helium, hydrogen, nitrogen, methane, and carbon dioxide) in various stationary liquid phases (SLP), such as pentadecane, polydimethylsiloxane PMS-100, and polyethylene glycol PEG-600, was studied. The carrier gases studied can be arranged in the following series by solubility in SLP: He<H₂<N₂<CH₄<CO₂. This order coincides with the series reflecting change in the retention values in GLC for different carrier gases. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 923–925, May, 1999.     

Viscosity of gases used as the mobile phase in gas chromatography

The vicosity-temperature relationship of the three gases (helium, nitrogen and hydrogen) most frequenly used as the carrier gas in gas chromatography is studied. Based on available data, equaitions are derived to describe this relationship. Using these equations viscosity data are tabulated for the chromatographically important temperature range.Dedicated to Professor A. Zlatkis on the occasion of his 60th birthday.     

Viscosities of carrier gases at gas chromatograph temperatures and pressures

Summary Equations are derived for viscosities of H₂, He, N₂ and Ar for use at chromatographic temperatures which are accurate to within 0.3% for H₂, and 0.1% for the other gases. The effect of pressure is usually negligible but may increase the viscosity of N₂ or Ar by as much as 0.5% at 25°C or lower and 5 atm or higher.     

Single fiber-in-capillary annular column for gas chromatographic separation

A method for preparation of a stationary phase-adjustable column with in-column stationary phase-coated fused-silica fiber annular column was successfully developed. The surface of a 0.12 mm o.d. bare optical fiber was first coated with a stationary phase and then inserted into a fused-silica capillary (non-coated or coated) as an annular column for gas chromatographic study. The optical fiber and capillary were coated with polydimethylsiloxane (SE-30) and polyethylene glycol 20M (PEG-20M) as nonpolar and polar stationary phases, respectively. Among the investigated annular and open tubular columns, the PEG-20M-coated fiber-in-PEG-20M-coated capillary annular column showed the highest column efficiency with a minimum plate height of 0.35 mm and an optimum gas velocity of 25 cm/s. When a SE-30/PEG-20M-coated fiber-in-uncoated capillary annular column was applied to separate a 9-component complex mixture, the total analysis time was 5.3 min and the column length was 12 m. By contrast, when a SE-30-coated fiber-in-PEG-20M-coated capillary annular column was used to separate the same 9-component mixture, the analysis time was reduced to 3.5 min and the column length was shortened by half to 6 m. Our results show that the stationary phase-coated fiber-in-stationary phase-coated capillary annular column is a better choice for gas chromatographic separation as it is more efficient and flexible. In addition, the proposed annular column design provides flexibility in using two or even more types of stationary phases to achieve optimal analytical separation.     

A GC-system for the analysis of residual geothermal gases

Summary The gases evolved from geothermal fields, after condensation of H₂O, CO₂, H₂S and NH₃ in caustic solution, contain He, H₂, Ar, O₂, N₂, CH₄ and higher hydrocarbons. The analysis for the major components in these residual gas mixtures can be achieved by use of two simple gas chromatographs in parallel, and using 5Å molecular sieve. The separation of He and H₂ to baseline is achieved by using low temperatures (30°C) coupled with a relatively long column; and the difficult separation of Ar and O₂ is achieved by use of a cryogenically cooled column. The use of switching valves to backflush and bypass columns ensures that a minimum time for analysis can be achieved whilst retaining baseline separations of the He/H₂ and Ar/O₂ pairs.     

Selectivity of polymer adsorbent in adsorptive separations of stevia diterpene glycosides

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Thin layer chromatographic separation of a few food dyes over scolecite as a new adsorbent

Summary A naturally occurring Zeolite mineral collected from Pawagad (Gujrat) india was shown to be a Scolecite of the natrolite group of Zeolites. After physico chemical characterization it was used as a new adsorbent for the separation of food dyes by TLC.     

高硫石油焦制备高储气性能天然气吸附剂

以高硫石油焦为原料,KOH为活化剂,十二烷基苯磺酸钠（SDBS）为表面活性剂制备天然气吸附剂,分析了高硫焦基吸附剂的孔结构和孔分布特征,讨论了高硫焦制备吸附剂的活化机理。结果表明,预活化中加入表面活性剂SDBS可提高KOH与原料的混合均匀度,对活化效果有利。最优活化条件下制备的吸附剂样品GSR3和GSR4的微孔容积分别达到1.0985cm3·g－1 和1.3193cm3·g－1,孔径分布集中在0.9nm~1.5nm;在25℃、充放气压力3.5MPa和0.1MPa下,GSR3、GSR4对甲烷的质量吸附量分别达到0.139和0.145,有效体积脱附量达到111和115。粉体高硫焦基吸附剂的性能非常接近于低硫焦基吸附剂。     

Evaluation of the surface properties of 4-(Decyloxy) benzoic acid liquid crystal and its use in structural isomer separation

The selectivity of 4-(Decyloxy) benzoic acid (DBA) liquid crystal in surface adsorption region (303.2–328.2 K) and thermodynamic region (423.2 – 433.2 K) was investigated by inverse gas chromatography at infinite dilution (IGC-ID). The selectivity parameters of the structural isomer series named butyl acetate, butyl alcohol, and amyl alcohol series were calculated for the DBA using IGC-ID technique. Additionally, the surface properties including dispersive surface energy (gS D), free energy (DGA S), enthalpy (DHA S), and acidity-basicity constants were calculated with net retention volumes obtained from IGC-ID experiment results. When the DHA S and DGA S are constants, DBA surface was found to be an acidic character (KD/KA @ 0.89).     

Separation of flavonoid and alkaloid using collagen fiber adsorbent

Flavonoids and alkaloids are two major classes of plant compounds with biological activities, and they usually coexist in many medicinal herbs. In this study, a novel collagen fiber adsorbent (CFA) was prepared, and its application for adsorption chromatography separation of flavonoids and alkaloids was systematically investigated. The typical flavonoids, rutin and baicalin, and the typical alkaloids, matrine and caffeine, were selected as probe molecules for the investigations. The batch adsorption behaviors of these compounds on CFA in different solvents indicated that hydrogen bond plays a predominant role for the adsorption of flavonoid and alkaloid in pure ethanol, while the hydrophobic interaction plays a predominant role for the adsorption in water. In column chromatography separation, flavonoids were completely separated from alkaloids by a stepwise elution process with pure ethanol followed by aqueous ethanol solution. The two flavonoids, rutin and baicalin, were also well separated although the two alkaloids, matrine and caffeine, were washed out together. The optimal loading volume of sample solution (10 mg/mL) for the separation was determined as 0.66 mL/g CFA. Under these conditions, flavonoid and alkaloid were effectively separated with a recovery higher than 90% in 8 times repeated applications.     

New method for calculating the adsorption of noble gases on amorphous surfaces

A new approach to calculating the equilibrium characteristics of the adsorption of noble gases on the amorphous surfaces of adsorbents was developed and applied to the Ar−TiO₂(rutile) system. Intermolecular adsorbate-adsorbate interactions are taken into account for the nearest neighbors in the quasi-chemical approximation. The lattice energy parameters of all interactions of the model are determined from the Lennard-Jones potential (12-6). The formation of amorphous TiO₂(rutile) surface includes completion of the surface layers and partial removal of the surface oxygen ions. The quality of the amorphization procedure was confirmed by the experimentally measured heats and isotherms of adsorption of the system under study. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1109–1118, June, 1997.     

笼形聚偕氨肟树脂吸附溴和碘

用酸、碱处理的笼形聚偕氨肟树脂（ACAO、BCAO）吸附溴和碘,发现它们的吸附能力无显著差别。吸附客量与溴和碘浓度关系符合Freundlich方程．从扫描电子显微镜观察到碘在树脂表面形成微晶．联系到溴和碘的超当量吸附现象,初步认为,它们是通过物理吸附在树脂表面富集。     

Membranes for separation of higher hydrocarbons from methane

In the search for a membrane material capable of separating higher hydrocarbons from methane about 40 different polymers were tested. The most promising two, polyoctylmethylsiloxane (POMS) and polytrimethylsilylpropyne (PTMSP), are compared in this article to the standard material polydimethylsiloxane (PDMS).     

A new look at light hydrocarbon separations on commercial alumina PLOT columns: Column selectivity and separation

Alumina-coated porous layer open tubular (PLOT) columns are widely used for analyses of light hydrocarbons (C₁ to C₆). There is, however, a need for improved selectivity for complex analyses such as the determination of impurities in high purity petrochemical products. Some commercial alumina PLOT columns do not have sufficient selectivity for such analyses. The selectivity of four commercial alumina PLOT columns is evaluated for analyses of propylene and ethylene, and differences in column selectivity discussed. Requirements of column selectivity and retention are presented for several applications including the analysis of refinery gas, transformer oil gas, and fuel gas.