Helium as a carrier gas

An important parameter when considering GC resolution of the sample components is the carrier gas linear velocity (flow rate, F), which can be determined by injecting 5-50 /A of argon or butane and measuring the time from injection to detection by the mass spectrometer. An optimum linear velocity using helium as a carrier gas is approximately 30 cm/sec and... 

The mass spectrum of primaquine diphosphate was obtained using a Shimadzu PQ-5000 mass spectrometer. The parent ion was collided with helium as a carrier gas. Figure 14 shows the detailed mass fragmentation pattern for primaquine diphosphate. Table 5 shows the proposed mass fragmentation pattern of the drugs. Clarke reported the following principal peaks at m/z 201, 81, 98, 175, 259, 176, 202, and 242 [2]. 

The column is operated at 230°C using helium as a carrier gas at the rate of 60 ml/min. The retention time of the drug is approximately 4 minutes. A flame ionization detector is used. n-Triacontane is used as an internal standard. 

Systematic diffusion experiments were also conducted with self-supported zeolite wafers (7-14 mg cm ) which were activated at 10 Pa and 675 K for 1.5 h. Prior to contact with the sorbate, the IR cell was filled with dried helium as a carrier gas. Subsequently, one or two components (benzene or ethylbenzene), carried by helium bubbling through thermostatted saturators, could be admitted. A system of mass-flow controllers allowed for an independent change of the partial pressures while the total pressure could be kept constant [22]. The time required to pass the sorbate from the inlet valve to the place of the zeolite wafer was about 4 s. IR spectra were obtained in intervals as short as 0.37 s. 

The most satisfactory column for estimating H2 was found to be a 6-foot length of Linde 13 X molecular sieves used in conjunction with argon as a carrier gas. The remaining components found to be present in significant quantities were CO2, CO, and CHU. These were estimated by using a 4-foot silica gel column in conjunction with helium as a carrier gas. This column was also found to be satisfactory for ethane however, this component was not present in sufficient quantity to be detected. 

The catalytic isomerization of -pentane was carried out in a once-through fixed bed flow reactor using helium as a carrier gas, at a standard temperature of 523 K in the absence and presence of dihydrogen in the feed. Characteristic rate and selectivity data are compared in Table 2 for WZ and PtWZ.21,35... 

Improvements in resolution on a capillary column after it has been prepared can be made only by the adjustment of retention time, which alters the partition ratio of the compounds, and by the optimization of the carrier gas used. Increases in retention time which result in a partition ratio of greater than 5 afford very little improvement in resolution and are done at the expense of analysis time. Similarly, the use of nitrogen instead of helium as a carrier gas results in an increase in resolution of 1.14 at the expense of doubling the analysis time. 

A gaseous mixture of CO ( C/ C = 0.011, natural abundance) and helium as a carrier gas was introduced into a small column of zeolite pellets for a selected time, then desorbed by evacuation of the column. 

If a purer compound is needed, HC=CD may be separated from C2H2 and C2D2 by gas chromatography . The best results are obtained with triethylamine supported on 60/80 mesh Chromosorb I at -78 C, employing helium as a carrier gas. After three runs, the product contains l -3% of C2H2 and less than 1% of C2D,. C2HD, stored at room temperature over mercury, is stable to disproportionation for several weeks at least. 

The feed was introduced by flowing dry helium as a carrier gas through a saturator containing freshly purified ethylbenzene kept at 25°C, to obtain an EB partial pressure of 10 Torr. Products were analysed by on-line G.C., using a column MBMA (Perkin Elmer), 30 m. The rate, r (mol- min l g"l) was calculated from r = Cq (F/W)-X, where c (mol- mP ), F (ml- min i), W ( g) and X (%) stand for the concentration of the feed, EB, at the inlet, flow rate, catal)ret mass and conversion, respectively. The contact time, F/W, was corrected for the flow at actual reaction temperature and reactor pressure. 

Reaction Studies. The reaction system consisted of a flow micro-reactor using helium as a carrier gas bubbled through a saturator containing 2-propanol. The partial pressure of 2-propanol was adjusted by controlling the temperature of the saturator. Approximately 200-400 mg of the layered hydroxide were heated In the reactor under a flow of helium In order dehydrate and dehydroxylate the material. The partial pressure of 2-propanol was maintained at 100 torr and the helium flow was varied between 10-20 ml/min. The in-situ calcination temperature was varied between 400-500°C and the reaction temperature between 150-350°C. Analyses of the reactants and the products were performed by an on-line GC fitted with a capillary column. 

Merck research grade H2S (5% vol.), alcohol (2,5 helium as a carrier gas and on line GC analysis. 

Continuous flow-isotope ratio mass spectrometry Gas source mass spectrometry where sample and standard gases are transported using helium as a carrier gas into the mass spectrometer for measurement of isotopic ratios. 

In regard to the question of calibration, a brief discussion will be given of the calibration curve for hydrogen with helium as a carrier gas. More detailed results will be reported elsewhere. The general character of the peak heights vs. increasing hydrogen concentration... 

Fig. 5. GC-MS chromatogram of the steam distilled volatile oil of the rhizome of C. aeruginosa. Camphor, isoborneol and borneol were eluted at 10.44,10.65 and 10.99min, their LRI were 1150,1160,1177, respectively. GC-MS system 1 pL (split mode 1 100) at 270 °C onto a TR-5 column using helium as a carrier gas at a flow rate of 1 mL.rnin-i. The oven temperature was programmed for 60 - 240 °C (4 °C.min-i) and 240 - 270 ° C (10 C.min-i) then held for 2 min. The detector and interface were maintained at 275 °C and the ion source at 220 °C and the MS scanned in positive ion mode over 35 - 650 m/ z. Obtained from the same instrument as Fig. 1.

The decay times measured In argon are longer than those observed with helium as a carrier gas. 

Pfab and Noffz [53] have described two methods, both based on GC, for the determination of styrene monomer and other volatiles in polystyrene. In one method an or /70-dichlorobenzene solution of the polymer is distilled to isolate volatiles as a concentrate in the distillate. The ortho-dichlorobenzene used to dissolve the polymer contains a known amount of toluene which is used as an internal standard. The distillate is chromatographed on a polyethylene glycol column using helium as a carrier gas and a katharometer detector. 

Catalytic Hydrogenations. The hydrogenations were carried out with a Parr hydrogenation apparatus at room temperature and hydrogen pressures of about 35 psL Cyclohexene, cis-cyclooctene, or 1-hexene (0.1 ml) was added to 20 ml methanol. The catalysts were added either as a colloidal diversion or as a solid after evaporation of the solvent. An amoimt of catalyst corre onding to 1 wt% platinum (with rei ect to cyclohexene, cis-cyclooctene, or 1-hexene) was added. The reaction mixtures were analyzed by gas chromatography (SE-30 packed column) with a flbme ionization detector, and helium as a carrier gas. 

Only one reference has been found in the literature to the direct gas chromatography of organozinc compounds. Longi and Mazzochi claim to have gas chromatographed this type of compound by gas chromatography on a 1-metre column of Chromosorb W containing 7.5% of paraffin wax (mp 63 - 64°C) triphenylamine (17 3) using dry purified helium as a carrier gas and a thermistor detector. 

Longi and Mazzocchi have gas chromatographed mixtures of lead, tin and antimony tetraethyl on columns comprising 7.5% paraffin wax on Chromosorb W at 143°C with an injection temperature of 196°C and using helium as a carrier gas. 

Turkel taub et al have described a gas chromatographic procedure for the determination of tricarbonylcyclopentadienyl-manganese, tritolyl phophate and various solvents in anti-detonator preparations. These are analysed on a column of Apiezon L on Celite 545, temperature programmed from 60 to 240 0 using helium as a carrier gas. 

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