Also referred to as ODs or reversed-Phase C18 Columns. This is a separation system that uses high performance liquid chromatography system (HPLC) with C18 as the main stationary phase substance. It is important to note that single stationary C18 phases will always be different from one C18 HPLC to the other.

The main difference between C8 and C18 column in HPLC is that the C8 column contains octyl carbon chain (C8)-bonded silica as the stationary phase, but the C18 column contains octadecyl carbon chain (C18)-bonded silica.

C8 and C18 both refer to the alkyl chain of a bonded face of a column. They are both used in the high performance liquid chromatography system. On the other hand, Octylsilane(C8) has only 8 carbon atoms on the column parking bonded to silica (Si). C18 will tend to retain more than C8.

C18, C8, and C4 are all linear alkylsilane phases. C18 is octyldecylsilane and contains 18 carbons bound to the silica. So they have more carbons and a longer carbon chain than C8 (8 carbons) or C4 (4 carbons). Because of the extra carbons, C18 has a larger surface area that the mobile phase has to travel across.

C18, C8, and C4 are all linear alkylsilane phases. C18 is octyldecylsilane and contains 18 carbons bound to the silica. So they have more carbons and a longer carbon chain than C8 (8 carbons) or C4 (4 carbons). Because of the extra carbons, C18 has a larger surface area that the mobile phase has to travel across.

Because of the extra carbons, C18 has a larger surface area that the mobile phase has to travel across. This offers more interaction time between the bonded phase and the elutes. Thus the sample elutes more slowly and has more separation.

What are C18 Columns? Also referred to as ODs or reversed-Phase C18 Columns. This is a separation system that uses high performance liquid chromatography system (HPLC) with C18 as the main stationary phase substance. It is important to note that single stationary C18 phases will always be different from one C18 HPLC to the other.