RAM Direct Injection
For the separation of small molecules in the presence of large biomolecules
HPLC analysis of small molecules contained within a protein matrix can be a difficult and time-consuming task. The analysis often involves multi-step pretreatment procedures including centrifugation, extraction and filtration. RAM (Restricted Acces Media) Direct Injection columns separate small molecules in the presence of much larger analytes without extensive sample pretreatment (Figure 1
). You can, therefore, directly inject a variety of complex sample matrices without prior sample clean-up for the separation and detection of drugs, drug metabolites, peptides and other analytes. (Figure 2
Eliminates multiple sample pre-treatment steps
As shown in (Figure 1
), RAM Direct Injection reduces the number of steps for sample preparation.
Use for variety of sample matrices
Efficient 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
Reduces potentially dangerous sample handling
Sample handling is significantly reduced, reducing the workers' threat to dangerous samples such as plasma, serum, urine and environmental samples
Reduces of biohazardous waste
RAM Direct Injection Phases
Porous silica supports are characterized as consisting of an external, directly accessible surface; and internal pores accessible only to molecules with an approximate molecular weight of less than 12,000 Daltons. 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 (Figure 3
). A dual surface configuration is especially important because the majority of the silica's surface area is in the pores. Figure 3
demonstrates the inner and outer layers of a typical ISRP phase.
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.