John W. Dolan

Questions from the e-mail bag are considered this month.

Questions from the e-mail bag are considered this month.

Questions from the e-mail bag are considered in this month's instalment.

Problems with retention-time drift, temperature control, and broad peaks from a new column are discussed.

Retention-time drift, temperature control and broad peaks from a new column are the topics of this month's discussion.

What do you do when the peak shape changes?

In a well-behaved method, changes in peak shape should occur gradually over hundreds or thousands of samples. Tailing of one or a few peaks usually points to a problem.

Will an internal standard always improve data quality?

What happens when the same method gives different retention times on different instruments?

Will an internal standard always improve data quality?

What do you do when an unexpected peak appears?

What do you do when an unexpected peak appears in the chromatogram?

What happens when the same method gives different retention times on different instruments?

What happens when the same method gives different retention times on different instruments?

Changing to a "better" liquid chromatography column may not always produce the expected results.

Changing to a "better" liquid chromatography column may not always produce the expected results.

No matter where LC is used, it is never immune to problems.

A mysterious autosampler problem is solved.

Liquid chromatography is never immune to unexpected problems.

This month, we look at calculating injection volume, choosing a wash solvent, and handling doubts about reference standard purity.

A look at situations in which retention times are too long, too short, or inconsistent

What causes peaks to appear where they do not belong?

Too much variability in your liquid chromatography method?

Too much variability in your liquid chromatography method?

How do you react to symptoms that indicate your liquid chromatography column has major problems?

How do you react to symptoms that indicate your liquid chromatography column has major problems?

What do you do when the system pressure is not what it is supposed to be?

A look at ways to estimate what normal system pressure should be and some likely causes of various pressure abnormalities

An exploration of how different variables affect a separation

For method development or routine analysis the minimum gradient time may be a limit of throughput.