A Brief History of the Hydrophobic Subtraction Model

Work on what is now known as the Hydrophobic Subtraction Model (HSM) was initiated by Dr. Lloyd Snyder and began informally in the late 1990's. The extensive expertise in and previous experience of Dr. Snyder and close collaborators Dr. John Dolan, Dr. Uwe Neue, and Professors Peter Carr and Dan Marchand with the subject of selectivity in HPLC supported a vision for a broader understanding of selectivity in Reversed-Phase HPLC (RPLC). This vision subsequently turned into a long-term project that led to the development of the HS model and characterization of hundreds of RPLC columns. The early stages of this project were supported financially by Phase I and II Small Business Innovative Research (SBIR) grants from the National Institutes of Health. The project has been highly collaborative from its inception, and has benefited immensely from involvement by innovators in the pharmaceutical industry, many manufacturers of HPLC columns, the Product Quality Research Institute (PQRI), and the United States Pharmacopeia. A database containing HS model parameters for hundreds of RPLC phases and an associated tool for finding columns of similar or different selectivity are also available at the USP website.

In late 2011, the work of characterizing of new stationary phases transitioned from the BAS laboratory in Oregon to the laboratory of Dr. Dwight Stoll at Gustavus College in Minnesota. Dr. Stoll currently maintains the HS database and is pursuing further development of the model with a number of collaborators. Column manufacturers interested in having their stationary phases listed in the HSM database should contact Dr. Stoll for more information.

About the Authors of this Website

Dr. Dwight Stoll is an Assistant Professor in the Department of Chemistry at Gustavus Adolphus College. His current research interests are focused on multi-dimensional separation methodologies and characterization of selectivity in HPLC.

Dr. Paul Boswell is acknowledged for his initial development of this site and contributions through 2015.


Snyder, L.R., Dolan, J.W., Marchand, D.H., Carr, P.W. The hydrophobic-subtraction model of reversed-phase column selectivity. Advances in Chromatography (Boca Raton, FL, U. S.) 2012 (50) 297–376.

Special Thanks To...

The National Institutes of Health

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