The hydrophobic-subtraction model of reversed-phase column selectivity

L. R. Snyder, J. W. Dolan, P. W. Carr

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350 Scopus citations


A recently developed treatment of reversed-phase column selectivity (the hydrophobic-subtraction model) is reviewed and extended, including its characterization of the selectivity of different column types (e.g., C 1-C 30, cyano, phenyl, etc.). The application of this model to retention data for various solutes and columns has provided new insights into the nature of different solute-column interactions and their relative importance in affecting sample retention and separation. Reversed-phase columns can be characterized by five selectivity parameters (H, S *, A, B and C), values of which are summarized here for more than 300 different columns. The selection of columns of either equivalent or different selectivity is readily achievable on the basis of their values of H, S *, etc. The development of the hydrophobic-subtraction model, its use in characterizing the selectivity of different reversed-phase liquid chromatography (RP-LC) columns, and its application to various practical problems as described here began in 1998. The original inspiration for this project owes much to Jack Kirkland, who also contributed actively to the initial studies that laid the foundation of this model; he has since provided other important support to this project. Jack and one of the authors (LRS) have enjoyed a strong professional relationship and personal friendship for the past 35 years, and it is the privilege of the authors to dedicate this paper and the work that it represents to Jack. His contributions to HPLC column technology have extended from the mid-1960s into the present century, and it is impossible to conceive of present day HPLC practice without Jack's contributions over the years. In this and other ways, his position as a pioneer and key implementer of HPLC is widely recognized. We wish Jack well in the years to come.

Original languageEnglish (US)
Pages (from-to)77-116
Number of pages40
JournalJournal of Chromatography A
Issue number1-2 SPEC. ISS.
StatePublished - Dec 10 2004

Bibliographical note

Funding Information:
It is appropriate to acknowledge the help of a number of different people and institutions, in the completion of the present 6-year study. First, 24 active participants in this project can be identified as the co-authors of eleven previous papers [4,5,10–12,30–33,72,75] . Second, almost every major column company has donated columns to this project for the measurement of values of H , S * , etc.; their names are provided in Table 13 . Third, a major part of the funding required for the work described in papers [4,5,10–12,30–33,72,75] was provided by Small Business Innovative Research (SBIR) grants from the National Institutes of Health. Fourth, we are much indebted to the Product Quality Research Institute and its membership for carrying out inter-laboratory comparisons of our column characterization procedure [30] , for examples of its application to practical assay procedures [72] , and for ongoing studies involving the selection of columns of greatly differing selectivity for use in orthogonal separations. Fifth, the coordination of early studies among different groups was supported by Nan Wilson of BASi, while Jonathan Gilroy of BASi has filled a similar critical role in later studies. Finally, we are indebted to Uwe Neue (Waters Corp.), Colin Poole (Wayne State University), Daniel Marchand and Ken Croes (University of Wisconsin, River Falls), and David McCalley (University of the West of England) for their help with the present paper.


  • Column selectivity
  • Hydrophobic-subtraction model
  • Retention models
  • Reviews


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