John W. Dolan

Where do you start when you encounter a problem with your LC system?

Rules of thumb for isolating problems, determining problem sources, and developing a maintenance routine.

What do you do when a peak grows over time?

A case of over-recovery of a preservative on ageing of a pharmaceutical product provides a good example of how to approach solving a problem of overlapping peaks in an LC separation.

Can pressure alone affect the appearance of a chromatogram?

Can pressure alone affect the appearance of a chromatogram?

Tips on what to consider when choosing another column to try and solve a tricky separation problem.

Comparisons between different C18 columns and the best way to select which one to use

A few simple calculations and estimates can provide insight into a troublesome chromatogram.

Apply the fundmentals to your problem and the cause may become obvious.

A change in the mobile phase strength can be a powerful tool to move peaks in a separation.

A change in the mobile phase strength can be a powerful tool to move peaks in a separation.

Examining the properties of the three most commonly used solvents and how to select the most suitable mobile phase composition.

Methanol and acetonitrile are the two most popular organic solvents to use in the mobile phase for reversed-phase liquid chromatography (LC) separations. Tetrahydrofuran is also used to a lesser extent. Why are these solvents the most popular ones? Are there alternative solvents that should be tried? This month's "LC Troubleshooting" examines these and some other aspects of solvent selection for LC.

If something doesn't look right you need to investigate!

John Dolan presents some practical pointers to get the most out of your UHPLC system.

An essential guide to getting the most from your UHPLC system.

John Dolan discusses an inquiry he received from a reader complaining about the difficulty he was having meeting system suitability for an LC method that had been transferred into his lab.

If something doesn't look right you need to investigate!

How to make gradient separations faster without changing the separation

Guest author Stefan Brand and John Dolan take a look at how to speed up gradient separations while avoiding common errors.

A broad peak where it does not belong is a classic sign of late elution.

Deterioration of the separation can result from many causes. This month's column looks at some techniques to isolate the problem source.

John Dolan looks at a case in which the peak doesn't seem to belong with the neighboring peaks in the chromatogram.

A broad peak where it doesn't belong is a classic sign of late elution.

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

This is John Dolan's 300th "LC Troubleshooting" column. Here, he takes a look through the archives.

John Dolan reaches a milestone with his 300th installment of "LC Troubleshooting" and takes a look back through the years.