James-Martin factor

In both cases, the James-Martin factor for the correction of gas compressibility under pressure difference between column inlet, pi, and column outlet, po, is introduced ... 

MARTIN-JAMES COMPRESSIBILITY FACTOR AND GIDDINGS PLATE HEIGHT... 

The following table provides the Martin-James compressibility factor, j,1 and the Giddings plate height correction factor, f,2 for chromatographically useful pressures. These quantities are defined as... 

Martin-James Compressibility Factor and Giddings Plate Height Correction Factor... 

Figure 10.5. Plot of James-Martin pressure-gradient correction factor / as a function of the compression ratio P = pjp0 for a GC column.

Where j is the James-Martin pressure-gradient correction factor... 

Prove that the James-Martin pressure-gradient correction factor j approaches zero as P- oo and approaches unity as 1. Deduce these limits on a physical basis using the result j = u/v0. 

In some cases of gas-liquid partition chromatography, as well as in the solid-liquid type just discussed, H bonds have been proposed as an important factor in achieving some separations. James (1031) describes successive passage through columns having stationary phases of differing H bond properties to separate 15 aliphatic amines. James, Martin, and Smith (1033) also effected separation of some amines by changing the liquid composition. Bradford, Harvey, and Chalkley (257, 884) used a similar method to separate unsaturated hydrocarbons. In this case, the... 

James-Martin pressure correction factor (compressibility factor)... 

If the mobile phase is a liquid, and can be considered incompressible, then the volume of the mobile phase eluted from the column, between the injection and the peak maximum, can be easily obtained from the product of the flow rate and the retention time. For more precise measurements, the volume of eluent can be directly measured volumetrically by means of a burette or other suitable volume measuring vessel that is placed at the end of the column. If the mobile phase is compressible, however, the volume of mobile phase that passes through the column, measured at the exit, will no longer represent the true retention volume, as the volume flow will increase continuously along the column as the pressure falls. This problem was solved by James and Martin [3], who derived a correction factor that allowed the actual retention volume to be calculated from the retention volume measured at the column outlet at atmospheric pressure, and a function of the inlet/outlet pressure ratio. This correction factor can be derived as follows. 

Diffusion is the dominant mechanism of lung deposition for radon daughter aerosols. It is generally assumed that airflow is laminar in the smaller airways and that deposition in each airway generation can be calculated adequately (Chamberlain and Dyson, 1936 Ingham, 1975). However, there is no such consensus on the treatment of deposition in the upper bronchi. Some authors (Jacobi and Eisfeld, 1980 NCRP, 1984) have considered deposition to be enhanced by secondary flow, on the basis of experimental results (Martin and Jacobi, 1972). It has been shown that this assumption reduces the calculated dose from unattached radon daughters by a factor of two (James, 1985). 

The net retention volume V, corrected for the pressure drop across the column by the gas compressibility factor of James and Martin (20) Is given by... 

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