Liquid Chromatography - The Retention Properties of Bulk and Brush Phases 2
It follows that the retention of the solute will depend only on the volume or surface area of the bonded material. Thus, providing all the bonded phase is available for solute interaction, the retention volume will be proportional to the carbon content of the phase. Scott and Kucera (28) examined a series of commercially available reverse phases and determined the carbon content of each phase and the retention volume of a series of solutes on columns packed with each adsorbent. The retentive properties of the five reverse phase are shown in figure 37 where the corrected retention volume (V'r) of 2-ethyl anthraquinone is plotted against carbon content of the reverse phase. It is seen, somewhat surprisingly, that there is a linear relationship between retention volume and carbon content of the brush phases (R2, R8, R18). This relationship can only be expected to occur if all the stationary phase is available to the solute and the packing procedure is very reproducible so that each column contains the same amount of packing.
Figure 37. Graph of Retention Volume against Carbon Content (%w/w)
It should again be stressed that all three reverse phases were produced from base silicas of very different surface areas and, despite this, the linear relationship between carbon content and corrected retention volume remained. This relationship may well depend, not only on the type of silica gel that is used but also on h bonding process and his relationship has not been proved generally.