Column inside diameter

Sample loading must be reduced in accordance with the column inside diameter. Polymers exhibit high solution viscosity, and in order to avoid band broadening due to viscous streaming the sample concentration must be reduced for narrow-bore columns. Overloading effects become noticeable at much lower concentrations using 4.6-mm columns compared to 7.5-mm columns because of the effective sample concentration in a smaller volume column. 

A typical column setup is shown in Figure 3.6. The heart of the system is, of course, the column of adsorbent. In general, the longer the column, the better the resolution of components. However, a compromise must be made because flow rate decreases with increasing column length. The actual size of a column depends on the nature of the adsorbing material and the amount of chemical sample to be separated. For preparative purposes, column heights of 20 to 50 cm are usually sufficient to achieve acceptable resolution. Column inside diameters may vary from 0.5 to 5 cm. 

HPLC columns are prepared from stainless steel or glass-Teflon tubing. Typical column inside diameters are 2.1, 3.2, or 4.5 mm for analytical separations and up to 30 mm for preparative applications. The length of the column can range from 5 to 100 cm, but 10 to 20 cm columns are common. 

The submitters used an 18-in. spinning-band column (inside diameter 10 mm.). The checkers employed a 12-in. helix-packed column. 

Impeller diameter on the figures in this chapter, m Note This parameter is identified as D in the text material.) Column inside diameter on the figures in this chapter, m Note This parameter is identified as T in the text material.) Diameter of the stage divider opening, m Diameter of the agitator shaft, m... 

Vertical length of draft tube, m Impeller speed, m/s Gas volumetric flow rate, m /s Column inside diameter, m... 

The relationship between capillary column inside diameter, column efficiency, expressed as the number of theoretical plates per meter (N/L), and film thickness is illustrated in Figure 7. These curves represent the theoretical limits of column efficiency for a given column inside diameter and stationary phase coating. The very thin-film, narrow-bore columns will be the most efficient and their efficiency changes markedly as the film thickness increases. The efficiency of a 0.25-mm i.d. column with a stationary phase film thickness of less than 1 pm is shown to be limited by mass transfer in the mobile phase (designated by Cg from the van Deemter equation), whereas mass transfer in the stationary phase (CL) becomes predominate in thick-film columns. The point at which Cg = CL is shown for narrow- and wide-bore capillary columns in Figure 7. 

Air containing 5 mol% NH3 at a total flow rate of 20 kmol/h enters a packed column operating at 293 K and 1 atm where 90% of the ammonia is scrubbed by a counter-current flow of 1500 kg/h of pure liquid water. Estimate the superficial gas velocity and pressure drop at flooding, and the column inside diameter and pressure drop for operation at 70% of flooding for two packing materials ... 

Figure 3. Calculated height equivalent to a theoretical plate, h, vs. log of the mobile phase velocity for a perfect analyte eluted on one capillary column with three different mobile phases. Assumptions are column inside diameter is 50 urn diffusion coefficients are 10 1 cm2/s for gas, 10-3 and 10-A cm2/s for low-and high-density supercritical fluid, respectively, and 10 cm /s for liquid.

Reversed-phase (RP) chromatography with an octadecyl-silyl column is usually employed for the separation of steroids from biological components. A conventional column (inside diameter, 4.0-4.6 mm) is used for LC-APCI-MS, whereas, because a low flow rate (0.05-0.2 ml/min) is required for ESI-MS detection, a semi-micro column (inside diameter, 1.0-2.1 mm) is usually employed in this mode. Methanol and acetonitrile are the most generally used organic modifiers for the mobile phase. In ESI-MS, acids (positive-ion mode) such as formic acid and acetic acid, bases (negative-ion mode) such as triethylamine or volatile salts (positive- and negative-ion modes) such as ammonium formate and ammonium acetate, are used as the mobile-phase additives to promote protonation or deprotonation of the analyte. 

Theoretically, when the linear velocity of the mobile phase is meant, then the value of N is independent of i.d. of the column. However, experimentally obtained results showed that the relationship between the mobile phase velocity and the maximum value of N varies, dependent on the column inside diameter. The maximum N for benzene in a polystyrene gel column with tetrahydrofuran was obtained at 0.4 mm/s, using a column of 1.5 mm i.d. [ref. 13]. Equation (9) predicts that the value of HETP decreases with decreasing packing particle diameter, dp, and that HETP is greatly Influenced by velocity with an increase in dp. These factors have been examined [ref. 14). When j-ica gels of 3 Um were used, the values of HETP for benzene were constant over 2 - 12.5 mm/s and increased as velocity decreased to less than 2 mm/s. 

The absorber is selected and the number of stages is set to six stages. The PR equation of state is selected for property measurements. Running the system leads to the process flow sheet and streams material balance shown in Figure 7.50. The estimated packed height and column inside diameter are shown in Figure 7.51. 

Solid Support—The support for use in the packed column is usually crushed firebrick or diatomaceous earth. Sieve size will depend on the diameter of the column used and liquid-phase loading, and should be such as would give optimum resolution and analysis time. Optimum size ranges cannot be predicted on purely theoretical grounds. For some systems it has been found that a ratio of average particle diameter to column inside diameter of 1 25 will result in minimum retention time and minimum band widths. 

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