John W. Dolan

In recent conversations at Pittcon 2010, it became clear to the author that sometimes we get too focused on the details of the method without backing up and determining how the fit into the big picture.

Look at the big picture. It may not be appropriate to obsess on the details

In this month's "LC Troubleshooting," the authors look at another use of calibration standards: to monitor the quality of the data, with a goal toward helping scientists troubleshoot instrument problems.

In order to improve LLOQ or LOD, or to increase precision in any case where S/N degrades precision, an increase in S/N will be beneficial. Here, John Dolan focuses on improvements in signal-to-noise.

Which is more important: signal or noise?

What can be expected when the column diameter is changed?

John Dolan examines some questions he recently received concerning the changes that took place in the 2009 edition of the United States Pharmacopoeia.

What can be expected when the column diameter is changed?

What to do when a peak is too small or too large

What should you do when a peak is too small or too large?

John Dolan looks at ways to get to the root of some of the most common problems encountered in the lab.

Where to place the blame when something goes wrong.

Where to place the blame when something goes wrong.

What's the best way to integrate a peak?

Remember the rule of one - change just one thing at a time.

John Dolan looks at the signal-to-noise ratio and its relationship to uncertainty in a measurment.

When is curve weighting a good idea?

This month's column discusses the type of problems one can encounter when using methods supplied to us by other.

Remember the Rule of One - change just one thing at a time

The best results depend on the correct choice of the calibration model.

This is the fifth and final installment in a series of columns about various aspects of calibration of LC methods.

Part IV of this series focuses on three different calibration models: external standardization, internal standardization, and the method of standard additions.

It's all in the perspective.

How are the signal-to-noise ratio and imprecision related?

This is the third installment in a series of LC Troubleshooting columns that focus on calibration curves used for LC methods. Here, John Dolan considers some alternate ways to look at the data to determine if they appear to be normal or are trying to tell us something is amiss.

In part two of this series, John Dolan looks at the signal-to-noise ratio and its relationship to uncertainty in a measurement.

Deciding on a zero intercept.

This month's "LC Troubleshooting" looks at some different calibration models, how to decide if a calibration curve goes through zero, and some problems that can occur if the wrong choices are made.

What measurements are required for system suitability?

This month's "LC Troubleshooting" discussion will center on the recommendations of the CDER document, especially in terms of what it means from a practical method performance standpoint.