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RAM Direct Injection Phases

Updated: Jun 17, 2021

A Tool for the Separation of Small Molecules in the Presence of Large Biomolecules.



Most conventional HPLC phases have a homogenous stationary phase on both silica surfaces. In contrast, the RAM phases are prepared by unique bonding processes that result in distinct inner and outer surfaces.


RAM direct injection advantage.

Eliminates multiple sample pretreatment steps The use of RAM Direct Injection HPLC columns eliminates the precipitation, centrifugation, solvent evaporation, and residue dissolution steps of typical procedures.

RAM phases employ a porous silica support that consists of an external, directly accessible surface and internal pores accessible only to molecules with an approximate molecular weight of less than 12,000 Daltons.


Small molecules contained within a protein matrix.

HPLC analysis of small molecules contained within a protein matrix can be a difficult and time consuming task. The analysis often involves multistep pretreatment procedures including centrifugation, extraction, and filtration. RAM Direct Injection allows for the chromatographic resolution of small molecules in the presence of much larger analytes without extensive sample pretreatment (figure 1). RAM Direct Injection HPLC columns eliminate prior sample clean up making it possible to directly inject a variety of complex sample matrices for the separation and detection of drugs, drug metabolites, peptides, and other analytes. .


RAM : Restricted Access Media

Simply filter the sample and inject directly onto the column.

• Works with a variety of sample matrices The RAM Direct Injection HPLC columns have demonstrated efficacy in the analysis of drugs, drug metabolites, peptides, and other analytes in matrices such as plasma, serum, whole blood, urine, plant and tissue extract, food and beverage, and environmental samples.

• Compatible with automated sample processing Simplified sample preparation and use of HPLC columns allow customers to employ automated systems.

• Reduces potentially dangerous sample handling With direct injection, sample handling is significantly reduced; therefore, potentially dangerous samples such as plasma, serum, urine, and environmental samples do not pose as significant a threat to the worker.

• Reduces biohazardous waste Use of SPE (solid phase extraction) disks can create biohazardous waste. RAM Direct Injection columns limit the creation of unnecessary biohazardous waste.

• Saves while it solves Because of the benefits described above, RAM Direct Injection often offers the lowest total cost solution.


A dual surface configuration is especially important because the pores provide the majority of the silica’s surface area. This dual-phase system allows for the separation of analytes through a combination of size exclusion and conventional phase partitioning. The outer surface employs both size exclusion and hydrophilic interaction to prevent large biomolecules from accessing the inner layer. As a result, these compounds elute from the column at the void volume. Small molecules penetrate through to the inner surface where they are retained and separated by the underlying hydrophobic support.



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