Sorbent Information: Mixed Phase Cation (MPC)

Mixed phase cation sorbent is a silica based particle that has been bonded with both a reversed phase group (octyl) and a strong cation exchange group (benzene sulfonic acid). This mixed phase chemistry, in which two primary modes of attraction are present, allows for a more efficient and selective extraction compared to traditional reversed phase techniques. Neutral and ionized analytes can be simultaneously extracted from a complex mixture and eluted as separate fractions. A mixed phase sorbent offers the following advantages:

• Eluting acidic and neutral analytes separately from basic analytes
• Selecting specific chemical interactions by nature of solvent and pH optimization to yield a more efficient extraction
• Providing cleaner chromatograms by allowing contaminants either to pass through or be retained on the sorbent

Applications: drugs of abuse antidepressants benzodiazepines antihypertensives antiarrhythmics opiates anticonvulsants antipsychotics stimulants

Chemical Structure

Product Usage

MPC sorbent is versatile and can be used in any of the following solid phase extraction schemes:

• Use selective elution solvents to elute acidic and neutral analytes in one fraction, followed by basic analytes in a separate fraction
• Use one elution solvent to elute a single analyte (or multiple analytes) selectively
• Use as a reversed phase sorbent and adsorb cationic interferences to the sulfonic acid group to obtain cleaner extracts for analysis

The successful use of mixed phase chemistry relies on adsorbing an analyte by either reversed phase and/or cation exchange interactions. The optimal analyte typically contains a hydrophobic region and at least one amine group that can be protonated. The pH at which the sample is loaded is very important to ensure that the amine group is fully protonated (sample pH should be at least 2 units below pKa of targeted amine group). When MPC sorbent is used in the reversed phase mode for a neutral analyte, it may be substituted into an existing method that now uses C18 or C8 bonded silica. An acidic analyte can be retained using reversed phase when the pH is lowered to make the analyte neutral.

Important Notes:

As a result of the dense particle loading within Empore membranes, proper use may require slightly higher vacuum or pressure than other SPE products. When used with a vacuum manifold, about 10 in Hg (254 mm Hg or 34 kPa) may be needed to pass solutions through the disk cartridge.