calculating bonding density from carbon load

[Jaycee]

In a research paper published on the Journal of Chromatography A (Characterization of phenyl-type HPLC adsorbents by Chan et al.,2005), the authors used the Berendsen-de Gara equation to calculate the bonding density of several Ph-type columns. However, I noticed that these columns do have a secondary bonding step after the primary bonding process with Ph groups, such as TMS or polar endcapping. Then in my opinion, the authors got overestimated values of the surface coverage of Ph functionality. Could anyone tell me if the authors made the right calculation? Sorry for my English and many thanks in advance

[Jaycee]

I've found an article in agreement with me, reading "…The ligand densities were calculated by the method of Berendsen and de Galan [67] and would represent an over-estimation of the ligand density because it does not take into account endcapping, especially in the case of the polar end-capped stationary phases, nevertheless it does offer a good comparison of the surface densities across the five phases…"(An assessment of the retention behaviour of polycyclic aromatic hydrocarbons on reversed phase stationary phases: Selectivity and retention on C18 and phenyl-type surfaces by Kayillo et al.,2006)
However, I wonder in this circumstance (TMS or polar end-capped) is there any more accurate approach to ligand density estimation by somewhat accounting for endcapping? Thanks for any insights, examples, or suggestions