Helium, as carrier gas

Should be distd under reduced pressure under nitrogen and stored in the dark. Purified via the nitrosochloride [Waterman et al. Reel Trav Chim Pays-Bas 48 1191 7929]. For purification of optically active forms see Lynn [J Am Chem Sac 91 361 1919]. Small quantities (0.5mL) have been purified by GLC using helium as carrier gas and a column at 90 packed with 20 wt% of polypropylene sebacate on a Chromosorb support. Larger quantities were fractionally distd under reduced pressure in a column packed with stainless steel gauze spirals. Material could be dried with CaH2 or sodium, and stored in a refrigerator CaS04 and silica gel were not satisfactory because they induced spontaneous isomerisation. [Bates, Best and Williams 7 C/iem Soc 1521 7962.]... 

The analysis of estrogens and progestogens by GC-MS has been carried out with a variety of capillary columns using helium as carrier gas [7,26,36,43, 59, 66]. LODs in the range of 0.1—1.8 ng L 1 have been achieved. In terms of sensitivity, GC- and HPLC-tandem mass spectrometry are comparable techniques. However, the derivatization carried out prior to GC separation is time consuming and can be a source of inaccuracy [7]. 

Nitrous oxide can be analyzed by GC on a molecular sieve column using a thermal conductivity detector and helium as carrier gas. It may be identified by GC/MS from its mass spectra. The molecular ion is 44. Also, it can be oxidized to NO and identified by the brown-ring test, using FeS04 solution, (see Nitric Oxide.)... 

A few gas chromatography (GC) and liquid chromatography (LC) studies have been reported. Eor example, PCDDs have been separated on a 50m x 0.25 mm polar fused silica capillary GC column (CP Sil-88, Chrompack) with helium as carrier gas and Fourier transform infrared (FTIR)/MS detectors <1997ANC1113>. Furthermore, a highly sensitive and accurate GC-MS method for rapid quantitative analysis of 1,4-dioxane in water has been described <1997JCH(787)283>. 

Murillo et al. (2004) studied the adsorption of phenanthrene (polycyclic aromatic hydrocarbon -PAH) from helium as carrier gas on a coke fixed-bed adsorber, at 150 °C. The isotherm of the phenanthrene-coke system at 150 °C was found to be of Freundlich type with Fr = 0.161 and KF = 1.9 (mol/kg)(m3/mol)0161. The isotherm has been derived for phenanthrene concentrations between 1.71 X 10 4 and 1.35 X 10-2 mol/m3. Finally, the average solid-phase diffusion coefficient, calculated from several experimental runs, was found to be 6.77 X 10-8 cm2/s. 

Comparison of Release Data with Proposed Model. A summary of the cesium release data obtained with helium as carrier gas is shown in Figure 5, where the percentage of cesium remaining is plotted vs, heating time on semilogarithmic coordinates. In all of the experiments the flow rate was maintained at 300 cc./min. and the temperature at 730° = = 5°K. The geometric parameters are indicated on each curve. Since only about 5% of the sodium was vaporized in each experiment, the assumption of a stationary liquid-phase boundary is justified. 

Heat the sample for 30 min at 30°C while purging helium at a rate of 25 ml/min. Collect volatile compounds on the trap (packed with Tenax or equivalent) and thermally desorb at 180°C onto a 30-m x 0.32-pm i.d. x 1-pm film thickness fused-silica capillary column. After desorption is complete, hold the initial temperature for 1 min at -20°C and then program the temperature to ramp to 220°C at 6°C/min. Set the injector and the detector temperatures at 260°C and 280°C, respectively. Use helium as carrier gas at a flow rate of 3.0 ml/min and a split ratio of 20 1. 

Fused silica capillary columns give better separation than packed columns. Columns having inside diameters of 0.25, 0.32, and 0.53 mm and film thickness between 0.25 and 1 pm have found use in herbicides analysis. The stationary phase is generally made out of phenyl silicone, methyl silicone, and cyanopropyl phenyl silicone in varying compositions. Some common columns are DB-5, DB-1701, DB-608, SPB-5, SPB-608, SPB-1701, Rtx-5, AT-1701, HP-608, BP-608, or equivalent. Use helium as carrier gas flow rate 30 cm/s on narrowbore columns with 0.25 or 0.32 mm ID and 7 mL/min for megabore 0.53 ID columns. 

Pauschmann, H. Gas chromatography determination of hydrogen using helium as carrier gas. Z. Anal. Chem. 203, 16 (1964). 

To determine Paraquat in agricultural run-off water Payne [194] separated the sediment from the sample (2L) by adding calcium chloride to aid flocculation, leaving the mixture overnight in a refrigerator for the sediment to settle. A 1L aliquot of the filtrate is extracted with dichloromethane. The dichloromethane extracts are concentrated by evaporation and the Trifluralin and Diphenamid are determined by direct injection, without further purification on to a glass column 1,8x6mm od packed with 10% DC 200 on Gas-Chrom Q and operated at 220°C with helium as carrier gas (lOOmL min-1) and a Coulson electrolytic-conductivity detector (N mode). Paraquat is determined in the filtrate by a modification of a conventional colorimetric method. Recoveries of the three substances were between 82 and 95% from water. 

Results. For O3, experiments were made with both nitrogen and helium as carrier gas in the pressure range of 29 to 85 torr, covering an effective diffusivity range of 1.46 to 5.61 cm /sec. Data were taken at three different temperatures, namely, 0, 10 and 19°C. The effects of added chemical reagent on the apparent accommodation coefficient,... 

Note 7. Both an SE-30 fused silica capillary column (30 m, 0.25 mm inner diameter, 0.25-// film thickness) and a similar, bonded dimethylsilicone column with helium as carrier gas (35-40cms 1 linear velocity) give good resolution. 

GLC analysis of the reaction products was carried out on an LHM-8MD chromatograph, equipped with flame-ionizing detector, using a 2mx3mm column (5% SE-chezasorb AW-HMDS as filler and helium as carrier gas) with temperatures ranging from 50 to 250 °C. 

To validate the results from the volumetric method, breakthrough experiments were also conducted using helium as carrier gas in columns packed with CMS samples. The volumetric data predicted the breakthrough performance very well, as may be seen from Figure 2. 

Arsine, present as an impurity in acetylene, has been determined on a column packed with tritolyl phosphate on Chromosorb 102 at 30 °C with hydrogen or helium as carrier gas, and thermal conductivity detection. Peaks were obtained for nitrogen, methane, arsine, hydrogen sulphide and phosphine. 

GC-MS (70 eV) analysis is possibly performed with a modern sensitive instrument equipped with a PEG-type bound-phase fused-silica (30 m x 0.32 mm i.d. 0.25 pm film thickness) capillary column, working with helium as carrier gas at flow-rate of 1.2mL/min, transfer line temperature 220 °C and MS source temperature 150 °C. Analysis is carried out in single ion recording (SIR) mode. In the optimized chromatographic conditions proposed by Fedrizzi et al. (2007a), the GC injector is set at a temperature of 250 °C and operates in splitless injection mode for 1 min the oven temperature is programmed to start at 35 °C (5 min), then increased by 1 °C/min to 40 °C, and finally increased by 10°C/min to 250 °C. 

All the reactions were monitored by gas chromatography (FID from Hewlett-Packard 5890II, cross-linked methyl silicone column 25mxO.2mmxO.33pm, helium as carrier gas 20 psi, injector temperature 230°C, detector temperature 250°C) using n-decane as internal standard. 

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