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The Carrier

Gas phase chromatography is a separation method in which the molecules are split between a stationary phase, a heavy solvent, and a mobile gas phase called the carrier gas. The separation takes place in a column containing the heavy solvent which can have the following forms ... [Pg.19]

The column is swept continuously by a carrier gas such as helium, hydrogen, nitrogen or argon. The sample is injected into the head of the column where it is vaporized and picked up by the carrier gas. In packed columns, the injected volume is on the order of a microliter, whereas in a capillary column a flow divider (split) is installed at the head of the column and only a tiny fraction of the volume injected, about one per cent, is carried into the column. The different components migrate through the length of the column by a continuous succession of equilibria between the stationary and mobile phases. The components are held up by their attraction for the stationary phase and their vaporization temperatures. [Pg.20]

This type of analysis requires several chromatographic columns and detectors. Hydrocarbons are measured with the aid of a flame ionization detector FID, while the other gases are analyzed using a katharometer. A large number of combinations of columns is possible considering the commutations between columns and, potentially, backflushing of the carrier gas. As an example, the hydrocarbons can be separated by a column packed with silicone or alumina while O2, N2 and CO will require a molecular sieve column. H2S is a special case because this gas is fixed irreversibly on a number of chromatographic supports. Its separation can be achieved on certain kinds of supports such as Porapak which are styrene-divinylbenzene copolymers. This type of phase is also used to analyze CO2 and water. [Pg.71]

To demodulate the signal, it is then necessary to multiply the carrier by itself. Of eourse, the carrier of the driver must be exactly the same as the demodulator one. But, as it is modified to be demodulated, we nevertheless need a common frequency reference for the driver and for the DSP. This reference is delivered by a quartz oscillator. [Pg.281]

In equations (3) and (4) the noise was simulated by sine function 6 = bs, (2nat), where a is the ratio of noise frequency to the carrier frequency of the reference signal. [Pg.830]

The efforts of the experts from Pivdenny have made it possible for Ukraine to become firmly established in the first three of space powers (after USA and Russia). More than 400 earth satellites developed in Pivdenny have been in space In recent years experts have developed the unique camer-rockets Zenith and Cyclone, capable of taking 4 and 14 tons into orbit, respectively. No other carrier-rockets of this type exist anywhere in the world, so they were selected for the international project Sea Start and Globalstar The NDT experts from Pivdenny have made a great contribution to these development, as practically all the parts and components of the carrier-rockets are subjected to thorough control. [Pg.970]

We will explore the effect of three parameters 2 -and < )> that is, the time delay between the pulses, the tuning or detuning of the carrier frequency from resonance with an excited-state vibrational transition and the relative phase of the two pulses. We follow closely the development of [22]. Using equation (Al.6.73). [Pg.238]

Figure Al.6.16. Diagram showing the directionality of the signal in coherent spectroscopy. Associated with the carrier frequency of each interaction with the light is a wavevector, k. The output signal in coherent spectroscopies is detemiined from the direction of each of the input signals via momentum conservation (after [48a]). Figure Al.6.16. Diagram showing the directionality of the signal in coherent spectroscopy. Associated with the carrier frequency of each interaction with the light is a wavevector, k. The output signal in coherent spectroscopies is detemiined from the direction of each of the input signals via momentum conservation (after [48a]).
The primary driver for the expansion of optoelectronic teclmologies is optical communications [2]. It was realized in the second-half of the 20th century that an increase of several orders of magnitude in bandwidth would be possible if optical waves were used as the carrier for telephone signals. The basic configuration of an optical communication... [Pg.2873]

The application of a small external electric field A to a semiconductor results in a net average velocity component of the carriers (electrons or holes) called the drift velocity, v. The coefficient of proportionality between E and is known as the carrier mobility p. At higher fields, where the drift velocity becomes comparable to the thennal... [Pg.2882]

In tenns of the carrier mobility, the electrical conductivity c of an n type semiconductor can be written as... [Pg.2882]

The carriers in tire channel of an enhancement mode device exhibit unusually high mobility, particularly at low temperatures, a subject of considerable interest. The source-drain current is carried by electrons attracted to tire interface. The ionized dopant atoms, which act as fixed charges and limit tire carriers mobility, are left behind, away from tire interface. In a sense, tire source-drain current is carried by tire two-dimensional (2D) electron gas at tire Si-gate oxide interface. [Pg.2892]

Initially, the only means of obtaining elements higher than uranium was by a-particle bombardment of uranium in the cyclotron, and it was by this means that the first, exceedingly minute amounts of neptunium and plutonium were obtained. The separation of these elements from other products and from uranium was difficult methods were devised involving co-precipitation of the minute amounts of their salts on a larger amount of a precipitate with a similar crystal structure (the carrier ). The properties were studied, using quantities of the order of 10 g in volumes of... [Pg.443]

Two different types of dynamic test have been devised to exploit this possibility. The first and more easily interpretable, used by Gibilaro et al [62] and by Dogu and Smith [63], employs a cell geometrically similar to the Wicke-Kallenbach apparatus, with a flow of carrier gas past each face of the porous septum. A sharp pulse of tracer is injected into the carrier stream on one side, and the response of the gas stream composition on the other side is then monitored as a function of time. Interpretation is based on the first two moments of the measured response curve, and Gibilaro et al refer explicitly to a model of the medium with a blmodal pore... [Pg.105]

The technique just described requires the porous medium to be sealed in a cell, so It cannot be used with pellets of irregular shape or granular material. For such materials an alternative technique Introduced by Eberly [64] is attractive. In Eberly s method the porous pellets or granules are packed into a tube through which the carrier gas flows steadily. A sharp pulse of tracer gas is then injected at the entry to the tube, and Its transit time through the tube and spreading at the exit are observed. A "chromatographic" system of this sort is very attractive to the experimenter,... [Pg.106]

Apparatus. The apparatus is made of Pyrex glass, in one piece. It consists of a shaped bulb A (Fig. 89 of about 30 ml. capacity in which the reaction takes place, provided with an inclined inlet B at the side and a vertical ascension tube D. B serves not only as an inlet for the admission of the carrier gas but also as the route by which the reagents and test sample are introduced into the apparatus. B ends in a small ground-glass joint into which fits ajoint carrying a capillary-tube which projects well down into the bulb A (the end of the capillary should be just above the liquid level when the apparatus is charged for the determination). The upper extension of this capillary beyond the joint is provided with a tap C to control the rate of flow of the carrier gas. [Pg.498]

To prepare the funnel G, fit it to the filter-flask and wash it by passing distilled water, ethanol and acetone through the glass plate H. Remove G from the bung J, wipe it with a clean cloth, and dry it in an oven for 15 minutes at 140°. Then carefully wipe it again with the cloth, and place it in the balance case on the carrier D (Fig. 90) for 15 minutes to attain an equilibrium with the air. Then transfer it to the balance pan and weigh. [Pg.504]

Method A. Cool a solution of the nitrate-free dichloride, prepared from or equivalent to 5 0 g. of palladium or platinum, in 50 ml. of water and 5 ml. of concentrated hydrochloric acid in a freezing mixture, and treat it with 50 ml. of formahn (40 per cent, formaldehyde) and 11 g. of the carrier (charcoal or asbestos). Stir the mixture mechanically and add a solution of 50 g. of potassium hydroxide in 50 ml. of water, keeping the temperature below 5°. When the addition is complete, raise the temperature to 60° for 15 minutes. Wash the catalyst thoroughly by decantation with water and finally with dilute acetic acid, collect on a suction filter, and wash with hot water until free from chloride or alkali. Dry at 100° and store in a desiccator. [Pg.948]

In gas chromatography (GC) the sample, which may be a gas or liquid, is injected into a stream of an inert gaseous mobile phase (often called the carrier gas). The sample is carried through a packed or capillary column where the sample s components separate based on their ability to distribute themselves between the mobile and stationary phases. A schematic diagram of a typical gas chromatograph is shown in Figure 12.16. [Pg.563]

In GC-MS effluent from the column is introduced directly into the mass spectrometer s ionization chamber in a manner that eliminates the majority of the carrier gas. In the ionization chamber all molecules (remaining carrier gas, solvent, and solutes) are ionized, and the ions are separated by their mass-to-charge ratio. Because each solute undergoes a characteristic fragmentation into smaller ions, its mass spectrum of ion intensity as a function of mass-to-charge ratio provides qualitative information that can be used to identify the solute. [Pg.571]

When a sample is injected into the carrier stream it has the rectangular flow profile (of width w) shown in Figure 13.17a. As the sample is carried through the mixing and reaction zone, the width of the flow profile increases as the sample disperses into the carrier stream. Dispersion results from two processes convection due to the flow of the carrier stream and diffusion due to a concentration gradient between the sample and the carrier stream. Convection of the sample occurs by laminar flow, in which the linear velocity of the sample at the tube s walls is zero, while the sample at the center of the tube moves with a linear velocity twice that of the carrier stream. The result is the parabolic flow profile shown in Figure 13.7b. Convection is the primary means of dispersion in the first 100 ms following the sample s injection. [Pg.650]


See other pages where The Carrier is mentioned: [Pg.21]    [Pg.71]    [Pg.830]    [Pg.132]    [Pg.809]    [Pg.809]    [Pg.1067]    [Pg.1247]    [Pg.1252]    [Pg.1253]    [Pg.1572]    [Pg.1573]    [Pg.2389]    [Pg.2861]    [Pg.2882]    [Pg.2890]    [Pg.2894]    [Pg.2895]    [Pg.105]    [Pg.482]    [Pg.503]    [Pg.505]    [Pg.50]    [Pg.573]    [Pg.1104]    [Pg.568]    [Pg.649]    [Pg.649]    [Pg.650]    [Pg.651]   


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Buffering Capacity of the Carrier Ampholytes

Charge carrier transport in the electrode-oxide semiconductor interfaces

Choice of the carrier

Concentration of the majority carrier

Detection involving the use of Au-NPs as carriers

Diffusion coefficient of the charge carriers

Floating Carriers—The Use of Hydrostatic Pressure

Fractionating the Carrier Ampholytes

Lifetime of the minority carriers

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Polymers as Carriers through the Blood-Brain Barrier

Positioning the carrier

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Requirements for the Carrier Materials

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The Ampholine Carrier Ampholytes

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The Carrier Range

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The Nature of Charge Carriers in Conjugated Polymers

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The Sequence of Electron Carriers

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The adenine nucleotide carrier

The discontinuous carrier gas flow procedure

The electrogenic carriers

The recombination of excess carriers

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