Regarding hybrid silica C18 columns, it shows a large efficiency loss from thermal friction. A 100 mm length column shows more than 50 MPa, so that the effect of frictional heat is larger compared to that with a 50 mm length column.
Some scientists wrote papers regarding efficiency loss by thermal friction. Totally porous hybrid silica showed the highest plate number at a low flow rate of 0.2 ml/min because of efficiency loss by thermal friction at a high flow rate. Totally porous silica particle catches influence of thermal friction less than totally porous hybrid silica particle.
This slide shows a comparison of separation of standard samples for 2 um or sub 2 um C18 columns as well as 2.6 um or 2.7 um core shell C18 columns. Regarding Separation Factor k6, company P and company W showed only 70% of retention factor of amylbenzene compared with SunShell C18. Company S shows almost the same retention factor as SunShell C18 although in regards to retention time, company S showed longer retention time than SunShell C18.
Pyridine peak shape was compared and the effect of residual silanol groups was evaluated. Mobile phase is methanol and water 30 to70. Number 2 peak is pyridine. SunShell C18 showed the best peak compared to the other C18's.
Oxine is a metal chelating compound. It is considered that Company P and Company S shows a low theoretical plate number and tailing. This means that they have a lot of metal impurities.
Company W has a bad peak shape.
SunShell C18 shows a good peak shape which shows that SunShell C18 has little metal impurities.