Liquid Chromatography

John Dolan

John Dolan is best known as one of the world’s foremost HPLC troubleshooting authorities. He has been responsible for training of thousands of scientists over the last 30 years, and is also known for his ongoing research with Lloyd Snyder, resulting in more than 100 technical publications and three books.

Recent Posts

Method Adjustment vs Change Part 7: Follow-up

This article considers the dilemma that occurs with any discussion regarding method alteration in that it can be open to interpretation.

Method Adjustment vs Change Part 6: Interactions

This technical article discusses the possible effect caused from interactions between changes from different variables.

Method Adjustment vs Change Part 5: Volume, Column Temperature and Detector Wavelength

This technical article discusses the injection volume, column temperature and detector wavelength adjustments.

Method Adjustment vs Change Part 4: Flow Rate and Particle Size

In this article we’ll look at flow-rate and particle-size adjustments.

Method Adjustment vs Change Part 3: Column Dimensions

In this article, we’ll take a closer look at some of the potential adjustments related to the column.

Method Adjustment vs Change Part 2: Aqueous-to-Organic Ratio

The second part of this series focuses on the allowable adjustment in the ratio of aqueous (A) to organic (B) components of a reversed-phase mobile phase.

Method Adjustment vs Change Part 1: Overview

In the first part of this series, an overview of the concept of method adjustment vs method change in reversed-phase HPLC is presented.

PEEK Fitting Slippage

PEEK (poly-ether-ether-ketone) fittings and tubing are in widespread use for HPLC applications. The convenience of using your fingers instead of a wrench to tighten the fittings and the flexibility of the tubing make PEEK the material of choice for...

Too Much Retention

As part of the HPLC Master Classes that I teach, I start each class by gathering questions or topics that the attendees would like to know more about. In a recent class in London, one of the topics was the causes of excessive retention – a method in...

Temperature and Retention

This technical article takes a closer look at the influence of temperature on the separation.

Back to Basics #10: Fundamental Resolution Equation – k

In the previous three instalments of this series ('#7: Fundamental Resolution Equation, Part 1', '#8: Fundamental Resolution Equation, N', '#9: Fundamental Resolution Equation – Alpha'), we’ve looked at the fundamental resolution equation

Back to Basics #9: Fundamental Resolution Equation – Alpha

In the previous two articles ('#7 Fundamental Resolution Equation, Part 1' and '#8 Fundamental Resolution Equation, N'), we’ve looked at the fundamental resolution equation

Back to Basics #8: Fundamental Resolution Equation, N

In the previous article we began our study of the fundamental resolution equation

Back to Basics #7: Fundamental Resolution Equation, Part 1

In our last Back-to-Basics discussion (#6 Resolution), we looked at the way we measure resolution, Rs, from a chromatogram using the following equation:

Solvent Nomograph

This technical article introduces the solvent-strength nomogram, a tool to pick the (approximately) equal strength of one solvent from another.

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