Packing chromatography, schematic

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. 

Schematic diagram of an injector for packed coiumn gas chromatography.

The basic instrument required for packed-column unified chromatography is shown schematically in Figure 7.9. This is essentially a two-pump HPLC instrument utilizing high-pressure mixing with just a few new components. At least one pump must... 

Figure 12.24 Schematic diagram of the multidimensional packed capillary to open tubular column SFC-SFC system. Reprinted from Analytical Chemistry, 62, Z. Juvancz et al., Multidimensional packed capillary coupled to open tubular column supercritical fluid chromatography using a valve-switching interface , pp. 1384-1388, copyright 1990, with permission from the American Chemical Society.

The recycle reactor is shown schematically in Figure 1. It consists of a catalytic or electrocatalytic reactor unit with a bypass loop, a recycle pump and a molecular sieve trap unit. The latter comprises one or two packed bed columns in parallel each containing 2-10 g of Linde 5A molecular sieve pellets. On line gas chromatography (Shimadzu 14A) was used for the analysis of CH4, O2, CO, CO2, C2H4 and C2H6 in the reactants and products. 

Filters. HN03 is efficiently trapped out on nylon filters. Typically, two or more filters are connected in series. A schematic of such a filter pack was shown in Fig. 11.22 (Anlauf et al., 1988). A Teflon filter first removes particles from the airstream and a nylon filter then removes gaseous HNO,. In this particular system, a third filter (Whatman 41 impregnated with an aqueous solution of glycerol and citric acid) was used to trap NH3. After sample collection, each of the filters is extracted separately and nitrate, ammonium, and additional particle components collected on the Teflon filter are measured by ion chromatography. The sensitivity of this method for nitric acid and the other species is determined in part by filter blank values (i.e., nitrate on unexposed filters) and by the total amount collected and hence the sampling time used. Times of... 

Figure 13.6 shows a schematic for IGC operation. Inverse, in this instance, refers to the observation that the powder is the unknown material, and the vapor that is injected into the column is known, which is inverse to the conditions that exist in traditional gas chromatography. After the initial injection of the known gas probe, the retention time and volume of the probe are measured as it passes through the packed powder bed. The gas probes range from a series of alkanes, which are nonpolar in nature, to polar probes such as chloroform and water. Using these different probes, the acid-base nature of the compound, specific surface energies of adsorption, and other thermodynamic properties are calculated. The governing equations for these calculations are based upon fundamental thermodynamic principles, and reveal a great deal of information about the surface of powder with a relatively simple experimental setup (Fig. 13.6). This technique has been applied to a number of different applications. IGC has been used to detect the following scenarios ...

In normal-phase chromatography, the retention is governed by the interaction of the polar parts of the stationary phase and solute. For retention to occur in normal phase, the packing must be more polar than the mobile phase with respect to the sample. Therefore, the stationary phase is usually silica and typical mobile phases for normal phase chromatography are hexane, methylene chloride, chloroform, diethyl ether, and mixtures of these. In reverse phase the packing is nonpolar and the solvent is polar with respect to the sample. Retention is the result of the interaction of the nonpolar components of the solutes and the nonpolar stationary phase. Typical stationary phases are nonpolar hydrocarbons, waxy liquids, or bonded hydrocarbons (such as Ci8, Q, etc.) and the solvents are polar aqueous-organic mixtures such as methanol-water or acetonitrile-water. In the strictest interpretation, normal and reverse phase are terms which only relate to the polarity of the column and mobile phase with respect to the sample as shown in Table 3-3 and drawn schematically in Figure 3-14. 

Figure 5 Schematic of a complete multiplexed and integrated instrumental design with eight capillaries. Stars at I, U1, and U2 represent the multiplexed freeze/ thaw valves. The T-assembly is made up of eight pieces of commercial junctions stacked together. These connect to the manifold M1, the SEC (size-exclusion chromatography) purification columns, and the reaction loops. The cross-assembly is made of eight pieces of standard crosses packed together with built-in heaters. V8 is an eight-position motorized titanium valve with a center port. S1 is a two-position motorized PEEK valve. V6 is a six-position motorized PEEK valve. (Reprinted from Ref. 33 with permission.)...

Specific and essentially stand-alone mode of liquid chromatography is associated with the absence or suppression of any analyte interactions with the stationary phase, which is called size-exclusion chromatography (SEC). In SEC the eluent is selected in such a manner that it will suppress any possible analyte interactions with the surface, and the separation of the analyte molecules in this mode is primarily based on their physical dimensions (size). The larger the analyte molecules, the lower the possibility for them to penetrate into the porous space of the column packing material, and consequently the faster they will move through the column. The schematic of this classification is shown in Figure 1-1. 

A schematic layout of a typical GPC unit is shown in Fig. 4.24. Since the elution rates by gravity flow through a vertical column, as in conventional chromatography, will be slow and nonreproducible, a mechanical pump is usually employed to force the sample and the elution solvent through the column at pressures of up to 1000 to 4000 psi and at a rate of 2 to 3 ml/min. The sample is injected into the column entry from a graduated hypodermic syringe (typically, 0.5 to 3 ml of a 0.005 to 0.1% solution of the polymer) by means of a mechanical inlet device. The pulse of the polymer solution injected into the column entry becomes diluted and attenuated as the different species are separated on the column packings. 

Figure. 4.18 Schematic layout of a typical gel permeation chromatography apparatus. It is, however, a normal practice to use a set of several columns each packed with porous gel particles having a different porosity, depending on the range of molecular sizes to be analyzed. (Adapted from Allcock and Lampe, 1990.)...

The technique differs from the standard gas chromatography only in the material used for the column packing and the processing of the data. The only additional hardware required are pressure gauges at the injection point and detector, which enable the k factor in Equation (3.4) to be calculated. A schematic diagram of an IGC is shown in Figure 3.8. 

The equipment for packed-column SFC is very similar to that for HPLC, whereas the instrumentation for capillary SFC is more reminiscent of gas chromatography. In Figure 43 a schematic diagram of packed-column SFC instrumentation is shown. It consists of a high-pressure pump, sample introduction system, oven, detector, restrictor, and recorder. In addition, a microcomputer is installed that controls temperature, flow, pressure, and density programming. 

The electrolytic water purifier is a layered EDI device with two discreet depletion chambers packed with various ion-exchange resins. It can be powered by an external low-voltage power supply or, most conveniently, by a built-in auxiliary power supply such as that provided by a Thermo Scientific Dionex ICS-2100 ion chromatography system at a constant current of 20 mA. Figure 10.90 shows the schematics of the EWP to be used in anion analysis. Feed water is... 

A schematic diagram of a typical hollow fiber dense membrane reactor is shown in Figure 37.5a. The hollow fibers (Figure 37.5b) are manufactured by a phase inversion process (OD = l.1-1.5 mm ID = 0.75-1 mm) [63,64]. The oxidant gas (O2, H2O, CO2, N2O) mixture is fed to the core side, while a fuel (CH4, CO, or H2) mixture is fed to the shell side. A catalyst can be packed on the shell side. Both exit hnes are continuously monitored by onhne gas chromatography or mass spectrometry. 

Fig. 3.21 Schematic illustration of gel-permeation chromatography column packed with beads.

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