Lloyd R. Snyder

How do non-alkylsilica columns provide us an additional dimension of column selectivity?

How do non-alkylsilica columns provide us an additional dimension of column selectivity?

When developing or modifying an LC separation, a common strategy is to change selectivity by choosing a new column. Here’s guidance for making that selection.

Reversed-phase liquid chromatographic columns can be compared quantitatively for differences in selectivity by means of the hydrophobic-subtraction model. This allows selection of columns that are either equivalent or different in selectivity. The present paper both presents a summary of this approach and shows in detail how to use it in practice.

A pioneer in high performance liquid chromatography reflects on his career and how "enlightened trial-and-error" can reduce the effort involved in method development.

A pioneer in high performance liquid chromatography reflects on his career and how "enlightened trial-and-error" can reduce the effort involved in method development.

We focus on the characterization of reversed-phase columns with particular emphasis on the hydrophobic-subtraction model

The coauthors discuss the various attributes of and approaches to reversed-phase chromatography.

We focus on the characterization of reversed-phase columns with particular emphasis on the hydrophobic-subtraction model

In the last part of this series, the authors provide a technical review of the means for method adjustment and the pertinent regulations concerning the required validation of adjusted methods.

In the first part of this series, the authors look at method modification from a scientific and regulatory standpoint with regard to changing a column and the operating parameters.

When a column is replaced with a new or "equivalent" column, sometimes the chromatogram can change so much that it is no longer suitable for its intended use. In such cases, method adjustment is necessary to correct the change. How much can the chromatographic variables be changed before revalidation is required? What do the regulatory agencies have to say about method adjustment? The authors discuss these issues and propose a technique that can be used to speed selection of new operating conditions.

Guest authors Lloyd Snyder and John Dolan describe a method for determining reversed-phase column selectivity.