ISRP
Internal Surface Reversed Phase (ISRP)
Developed by Dr. Thomas Pinkerton, this material was created specifically for the direct analysis of drugs in serum without extensive sample preparation. The result was a new phase that allows for chromatographic separations without interference by protein adsorption. The efficacy of the GFF II phases has been demonstrated in a variety of applications, including the study of drugs, their metabolites, and the resolution of peptides.
Continuing product improvement efforts resulted in the development of the ISRP GFF II, a second generation phase with an improved bonding process ― bonding the GFF peptide to the silica surface through a monofunctional glycidoxypropyl linkage rather that the original trifunctional linkage. 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.
| Product | Particle Size | Column Dimensions | Regis
Product # | U.S. Price |
|
| GFF II | 5 µm, 80 Å | 15 cm x 4.6 mm i.d. | 731471 | $880.00 |  |
| GFF II | 5 µm, 80 Å | 25 cm x 4.6 mm i.d. | 731472 | $1,165.00 | |
| GFF II | 5 µm, 80 Å | 5 cm x 2.1 mm i.d. | 731469 | $550.00 | |
| GFF II | 5 µm, 80 Å | 5 cm x 4.6 mm i.d. | 731470 | $595.00 | |
GFF II Guard
Cartridges** | 5 µm, 80 Å | 1 cm x 3.0 mm i.d. | 731474 | $195.00 | |
| GFF II Guard Kit* | 5 µm, 80 Å | 1 cm x 3.0 mm i.d. | 731475 | $290.00 | |
* Includes 1 holder and 2 guard cartridges
** Includes 3 guard cartridges |