Carrier gases for

The penetration and film-penetration theories have been developed for conditions of equimolecular counterdiffusion only the equations are too complex to solve explicitly for transfer through a stationary carrier gas. For gas absorption, therefore, they apply only when the concentration of the material under going mass transfer is low. On the other hand, in the two-fihn theory the additional contribution to the mass transfer which is caused by bulk flow is easily calculated and hp (Section 10.23) is equal to (D/L)(Cr/Cum) instead of D/L. 

The electron capture detector is another type of ionization detector. Specifically, it utilizes the beta emissions of a radioactive source, often nickel-63, to cause the ionization of the carrier gas molecules, thus generating electrons that constitute an electrical current. As an electrophilic component, such as a pesticide, from the separated mixture enters this detector, the electrons from the carrier gas ionization are captured, creating an alteration in the current flow in an external circuit. This alteration is the source of the electrical signal that is amplified and sent on to the recorder. A diagram of this detector is shown in Figure 12.13. The carrier gas for this detector is either pure nitrogen or a mixture of argon and methane. 

Nitrous oxide is used for induction and maintenance of anaesthesia. It is widely used as carrier gas for other volatile agents in general anaesthesia. The usual concentra-... 

Place column in gas chromatograph and purge with carrier gas for 10 h. 

Similar to the analytical procedure for trace analysis in high purity GaAs wafers after matrix separation, discussed previously,52 the volatilization of Ga and As has been performed via their chlorides in a stream of aqua regia vapours (at 210 °C) using nitrogen as the carrier gas for trace/matrix separation.58 The recoveries of Cr, Mn, Fe, Ni, Co, Cu, Zn, Ag, Cd, Ba and Pb determined after a nearly quantitative volatilization of matrix elements (99.8 %) were found to be between 94 and 101 % (except for Ag and Cr with 80 %). The concentrations of impurities measured by ICP-DRC-MS (Elan 6100 DRC, PerkinElmer Sciex) after matrix separation were compared with ICP-SFMS (Element 2, Thermo Fisher Scientific) and total reflection X-ray fluorescence analysis (TXRF Phillips). The limits of detection obtained for trace elements in GaAs were in the low ngg-1 range and below.58... 

Figure 4.26 shows a flow reactor of diameter D in which the downstream portion of the walls is catalytic. Assume that there is no gas-phase chemistry and that there is a single chemically active gas-phase species that is dilute in an inert carrier gas. For example, consider carbon-monoxide carried in air. Assume further a highly efficient catalyst that completely destroys any CO at the surface in other words, the gas-phase mass fraction of CO at the surface is zero. Upstream of the catalytic section, the CO is completely mixed with the carrier (i.e., a flat profile). The CO2 that desorbs from the catalyst is so dilute in the air that its behavior can be neglected. Thus the gas-phase and mass-transfer problem can be treated as a binary mixture of CO and air. The overall objective of this analysis is to... 

Are there potential benefits to changing the fraction of Cd in the carrer gas Are there benefits to changing the carrier gas, for example, to nitrogen ... 

Expose hot fiber to carrier gas for fixed time (column is cold)... 

P 3] The liquid methanol water mixture leaves the storage tank and enters the evaporator together with nitrogen which is used as carrier gas for the evaporated... 

Oxygen is used for the correction of hypoxia and as a diluent or carrier gas for vapors and gases, primarily anesthetic agents. The use of oxygen at increased pressure is termed hyperbaric oxygen therapy. This therapy is used in diverse conditions such as multiple sclerosis, traumatic spinal cord injury, cerebrovascular accidents, bone graft, fractures, and leprosy. However, there are no available authentic data, as there are no well-controlled clinical trials. 

Gas Chromatography. The basic components of a gas chromatograph are a carrier gas system, a column, a column oven, a sample injector, and a detector. Very pure helium is the near-universal carrier gas for environmental and many other analyses. Open tubular GC columns are constructed of fused silica with low-bleed stationary phases of varying polarity chemically bonded to the silica surface. Columns are typically 30-75 m in length and have inside diameters (ID) in the range of about 0.25-0.75 mm. The column oven is capable of precise temperature control and temperature programming at variable rates for variable times. 

Note Chromosorb 104 is oxygen sensitive. Both new and used columns should be flushed with carrier gas for 30 to 60 min before heating each time they are installed in the gas chromatograph. 

The Role of Oxygen. To define properly the role which 02 played in these ozonolysis reactions, nitrogen was occasionally used as the carrier gas for ozone. After ozonizing n-hexylmercuric bromide at 10°C with the usual 03—02 mixture, the reaction was repeated with 03—N2 (see Experimental). By comparing the reaction products from runs 6 and 7 (Table I), it can be readily seen that no product differences exist when N2 is substituted for 02. 

Argon or hydrogen at various amount of substance flow rate relations a (nH MTs) or P (oaf Omjs) was used as carrier gas for the MTS. The influence of temperature, amount of substance flow rate relation a or P and residence time t was also investigated. The experimental identification of the reaction components is required to formulate a reaction mechanism and to compare with thermodynamic calculated gasphase composition. Knowledge of the individual running reactions should make the specific influence on the deposition of SiC layers possible. 

Another strategy to improve transport efficiency of the Ba(thd)2 and process reproducibility is to use NH, which is a simple amine adduct, as a carrier gas for the precursor. This idea was suggested by A. Baron in 1990 for the MOCVD of high T, superconducting oxide films containing Ba ions. J. S. Lee et al. recently reported in - situ mass spectroscopic analysis results of the MOCVD of SrTi03 thin... 

---