Gas Chromatography-Source of the Velocity-Independent A Term in the Van Deemter Equation

Solid Support Characteristics and Plate Height in Gas Chromatography.

“…In the derivation of the van Deemter equation, finite rate of mass transfer in the gas phase was omitted because estimates indicated that its contribution would be negligible compared to that of the liquid phase. or less than dp have been found by many workers (1,7,8,15,32,33,45,56) while others have apparently found negative A values (7,33,52,60). Some evidence has been presented that indicates that A is velocity dependent (7,35,60).…”

Modifications to the van Deemter Equation in Gas Chromatography

“…In some cases, (5, 9) the £q term is present in experi mental curve fits ; sometimes it is not. As the R values for NM were quite small for the direct fit of Equation 32, and since NM invariably appeared as a skewed (tailing) peak, it is thought that Kieselbach's (20) suggestion that the cause of the Pq term is either due to component remixing in the dead volume of the column and sample side of the detector or to channeling or wall effects in the packing is correct. In either case, the peak asymmetry would increase with decreas- Table 6 as shown below.…”

Modifications of the van Deemter equation in gas chromatography

“…In some cases, (5,9) the £q term is present in experi mental curve fits ; sometimes it is not. As the R values for NM were quite small for the direct fit of Equation 32, and since NM invariably appeared as a skewed (tailing) peak, it is thought that Kieselbach's (20) suggestion that the cause of the Pq term is either due to component remixing in the dead volume of the column and sample side of the detector or to channeling or wall effects in the packing is correct. In either case, the peak asymmetry would increase with decreas-…”