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The direct analysis of drugs in serum without extensive sample preparation.

Updated: Jun 18, 2021

Developed by Dr. Thomas Pinkerton, the result was a new phase that allows for chromatographic separations without interference by protein adsorption.

A second generation phase with an improved bonding process—bonding the GFF peptide to the silica surface through a monofunctional glycidoxypropyl linkage rather than the original trifunctional linkage.

ISPR : Internal Surface Reversed Phase.

This resulted in the following improvements:

• Increased sample retention

• Higher column efficiency

• Greater batch-to-batch reproducibility.


ISRP Selectivity


Many variables can affect the selectivity of the ISRP phase, including:


Mobile Phase Composition: The nature of ISRP analytes requires that mobile phases consist of a buffer with varying degrees of modification. Modifiers can include acetonitrile, methanol, isopropanol and tetrahydrofuran. Caution: too much modifier can result in matrix precipitation.


pH: The pH of the mobile phase can be controlled to avoid protein denaturing and to enhance selectivity. The pH range of the column is between 2.5 and 7.5; however, within the optimal pH range of 6.0 to 7.5, both the proteins and the glycine outer surface take on a negative charge. As a result, negatively charged proteins are repulsed by the outer phase and pass quickly through the column.


Temperature: Separations can also be optimized by varying column temperature. Lower temperatures have been shown to result in increased retention and selectivity.

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