Internal column diameter

Column internal diameter Volumetric flow rate Injection volume UV-deteaor cell volume Sensitivity improvement... 

INFLUENCE OF COLUMN INTERNAL DIAMETER ON EFFICIENCY AMD SEPARATION TIME FOR OPEN TUBUALR COLUMN SUPERCRITICAL FLUID CHROMATOGRAPHY. 

Note not all combinations of stationary phase, column internal diameter, and column length are available. For analytical comparisons, see References 36 and 37. Names of columns and/or stationary phases may be trademark protected. N/A = not available. ID = inner diameter. 

Column internal diameter (dc) None if linear gas velocity the same Narrower column sharper peaks... 

Miniaturizing the column i.d. is of great benefit to the sensitivity of ESl-MS, which behaves as a concentration-sensitive detection principle, because the concentration of equally abundant components in the LC mobile phase is proportional to the square of the column internal diameter. Column diameters from 150 to 15 jm with flow rates 20-200nL improve detection limits of peptides 1-2 orders magnitude over microliter flow rates. Several references referred to in other sections of this chapter discuss the use of LC-ESI MS to characterize separation products. and a sample chromatogram from Ito and coworkers. is seen in Figure 3.8. Table 3.4 provides additional and references that have used this technique. 

With open tubular columns, permeability is given by Poiseuille s law, B = dll32, where dc is the column internal diameter. 

The absorption column is sized according to two key parameters, these are to design for optimum mass transfer and optimum unit cost. A column internal diameter can be estimated according to the liquid and gas flowrates by utilizing graphs and nomographs such as those contained in Ref. A3. These recommendations have been refined using a computer-based mathematical model. The model predicts the required number of trays for a specified column internal diameter. These results enable a compromise to be achieved between tower cost and tower performance. 

After selection of the column internal diameter (the fundamental column specification), the sieve plates must then be designed. This involves a trial and error approach. A preliminary plate design is proposed based upon typical tray configurations, then the hydraulic... 

The sieve-plate weir length is taken as 0.8 times the column internal diameter (Ref. A5, p.14). The downcomer area is sized using a graph relating downcomer area and weir length (Ref. A3, Figure 11.31), and is found to be 15% of the column area. 

Reference A3 details the recommended plate configuration for liquid flowrate versus column internal diameter. This suggests a single-pass crossflow-type sieve plate as shown in Figure 9.1. 

Reference A3 (Figure 11.28) details the recommended plate configuration for liquid flowrate versus column internal diameter. A reverse flow-type sieve plate is suggested as shown in Figure 9.3. The pitch of the sieve-tray holes is selected so that the total hole area is reduced to 0.07 times the total column area. The other design criteria employed to provide the provisional plate specification are detailed in Table G,3. 

DIA, s = required extractor column internal diameter for solvent phase, ft... 

Equations (7.26) and (7.27) are based on 80% extractor column flood. (Note the 0.8 factor in both equations.) Please note that Vc and VD are the superficial full-column internal diameter velocities. Superficial simply means that you calculate these velocities as though the respective liquid phase were the only material in the full-column cross-sectional area... 

Load the sample on an appropriate RP column (internal diameter of the column chosen according to the starting biological material available, 300 A for granulometry, internal diameter from 3.8 to 7 mm, a Ci8 or C8 column is recommended for step 1). It is recommended to equilibrate the column with 2% acetonitrile in acidified water (0.05 % TFA) to remove the hydrophilic molecules and to properly stack the interesting material. 

Small-bore columns for HPLC are categorized in terms of the column internal diameter. There are four types of small-bore columns narrow-... 

Gas absorption is a function of the gas and liquid mass transfer coefficients, the interfacial area, and the enhancement due to chemical reaction. The gas-liquid interfacial area is related to the Sauter mean bubble diameter and the gas holdup fraction. The gas holdup fraction has been reported to vary with radial position (7-11) for column internal diameters up to 0.6 m. Koide et al" Tl2), however, found that the radial distribution of gas holdup was nearly constant for a column diameter of 5.5 m. Axial distribution of average gas holdup has been reported by Ueyama et al. (10). The average gas holdup... 

A comparison of monolithic conventional size, microbore, and capillary poly(p-methylstyrene-co-l,2-bis(p-vinylphenyl)ethane) columns confirmed that the efficiency for analysing proteins and oligonucleotides improved with decreasing column internal diameter, even if monolithic capillary columns up to 0.53 mm internal diameter were successfully used for the fractionation of the whole spectrum of biopolymers including proteins, peptides, and oligonucleotides as well as double-stranded DNA fragments under IPC conditions [14,23]. 

Modem GC uses capillary columns (internal diameter 0.1-0.5 mm) up to 60 m in length. The stationary phase is generally a cross-linked silicone polymer, coated as a thin film on the inner wall of the fused silica (Si02) capillary at normal operating temperatures, this behaves in a similar manner to a liquid film, but is far more robust. Common stationary phases for GC are shown in Fig. 32.4. The mobile phase ( carrier gas ) is usually nitrogen or helium. Selective separation is achieved as a result of the differential partitioning of individual compounds between the carrier gas and silicone polymer phases. The separation of most organic molecules is influenced by... 

Fig. 32.5 Influence of GC column internal diameter on separation 1. phenol 2. 2-chlorophenol 3. 2-nitrophenol 4. 2,4-dimethylphenol 5. 2,4-dichlorophenol 6. 4-chloro-3-methylphenol 7. 2,4,6-trichlorophenol 8. 2,4-dinitrophenol 9. 4-nitrophenol 10. 2-methyl-4,6-dinitrophenol 11. pentachlorophenol.

Selecting an appropriate column for capillary GC is a difficult task and one which is usually left to the technician. However, it is important to be aware of some general issues and what influence they can have on the separation. The column internal diameter can affect both resolution and speed of analysis. Smaller internal diameters columns (0.25 mm i.d.) can provide good resolution of early eluting peaks (Fig. 32.5a). However, the problem is that the analysis times of the eluting components may be longer and that the linear dynamic range (see p. 210) may be restricted. In contrast. 

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