Monomeric HPLC Columns
Refers to monomeric funtionalization of stationary phase. Function groups, e.g., C18, is covalently bonded to stationary phase. Silica is the most popular stationary phase in HPLC column. Chlorodimethylsilane is used to form a single bond between the functional group and the silica stationary phase. Endcapping can be performed to further minimize silanol activities.
Monomeric stationary phase has good batch-to-batch reproducibility, good hydrophobic properties, often cheaper than polymerics, making it popular. The silanols contribute to the selectivity of the column. However, too much silanols may cause tailing in some samples. Endcapping is often used to minimize silanol activity. It is mostly used for analyses of pharmaceutical molecules,analgesics, antidepressants, herbicides, or immunosuppressants
Monomeric stationary phase is less stable than polymeric in low pH. Silane hydrolysis can occur more easily in monomeric stationary phase causing leaching and short column life time. The low pH range for a monomeric stationary phase is often cited as pH 2.0 by most manufacturers.