John W. Dolan

Two different methods of calculating the LLOQ disagree. Which, if either, is correct?

A look at liquid chromatography in the past, what it has become today, and where it is going in the future

What's happened in the last 30 years? What will happen next?

How do you identify the cause of unstable retention times?

This troubleshooting study of a problem of retention time variation provides a good example of how to track down the source of a problem and how to speculate on probable cause.

In contrast to isocratic separations, gradient elution can sometimes seem to be counter-intuitive. Yet with the proper perspective, the things we intuitively understand about isocratic methods apply in a similar manner to gradients.

Where do all those extra peaks come from?

Where do all those extra peaks come from?

Can anything be done to correct for baseline drift in gradient separations?

Can anything be done to correct for baseline drift in gradient separations?

In contrast to isocratic separations, gradient elution can sometimes seem to be counter-intuitive. Yet with the proper perspective, the things we intuitively understand about isocratic methods apply in a similar manner to gradients.

Gradient methods can offer unique solutions to separations problems, but transferring a gradient method from the literature, between laboratories, or even within the same laboratory can be a challenging process.

How can the gradient dwell volume impact results?

Sometimes when changes are made to gradient conditions, the result isn't what was expected.

Sometimes when changes are made to gradient conditions, the result isn't what was expected.

Is it possible to get the same separation under isocratic and gradient conditions?

Is it possible to get the same separation under isocratic and gradient conditions?

In contrast to isocratic separations, gradient elution can sometimes seem to be counter-intuitive. Yet with the proper perspective, the things we intuitively understand about isocratic methods apply in a similar manner to gradients.

A how-to on understanding gradient elution

It is important to consider the influence of the sample matrix when setting up an analytical method

How to account for the sample matrix when developing a method

The use of a gradient scouting run can be a powerful tool to jump-start method developent. But what conditions should be chosen, and what do we do with the results?

How to choose conditions and what to do with the results

The refractive index detector can be frustrating to use because of its extreme sensitivity to temperature and other variables. However, it can see things that no other detector can see.

A description of how refractive index detectors work and some good practices to get the most out of this powerful detector

The solvent chosen for injection can affect the apearance of chromatographic peaks.

How can we tell if an LC method is working properly?

How can we tell if a liquid chromatography method is working properly? How can a compendial method be adjusted to speed up the run time?

The solvent chosen for injection can affect the appearance of chromatographic peaks.

A closer look at how the solvent chosen for injection can affect the appearance of chromatographic peaks.