John W. Dolan

Have a problem with your LC system? Maybe applying a little "DDT (Don't Do That)" may help.

Have a problem with your LC? Maybe applying a little DDT may help.

Make your column last forever? Not quite, but you can help prevent its early demise. 

How large an injection can you make if the injection solvent is not matched to the mobile phase?

How large an injection can you make if the injection solvent is not matched to the mobile phase?

What symptoms might indicate we have an injection problem?

Both the volume of the sample injection and the solvent in which the sample is dissolved can affect the appearance of the chromatogram.

How can resolution be determined when peak width cannot be measured?

How can resolution be determined when peak width cannot be measured?

A fast, sensitive and accurate quantitative method was developed using HPLC–MS–MS for analysis of phthalate metabolites in urine samples.

Small changes in retention time with an LC method are normal. At what point is a problem suggested?

Why should you be concerned about mobile-phase degassing?

Why should you be concerned about mobile-phase degassing - it's all done automatically, isn't it?

To solve problems with UV detectors, it helps to understand a few things about how the detector cells are designed.

UV detectors are the most common LC detector, and perhaps the most reliable ones. But they are not without problems.

This month's "LC Troubleshooting" instalment looks at two reader-submitted questions regarding method calibration.

A look at two reader-submitted questions regarding method calibration

Some attributes of large molecules make them behave differently from small molecules in reversed-phase separations.

Some attributes of large molecules make them behave differently from small molecules in reversed-phase separations.

If scaling isocratic separations is so simple, why is gradient scaling so confusing?

If scaling isocratic separations is so simple, why is gradient scaling so confusing?

What kind of adjustments need to be made when scaling an isocratic method?

What kind of adjustments need to be made when scaling an isocratic method?

What good is that big, ugly peak at the beginning of the chromatogram?

What good is that big, ugly peak at the beginning of the chromatogram?

Why do some peaks front and others don't in the same method?

Why do some peaks front when others don't - in the same method?

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

How to evaluate a calibration curve and calculate the lower limit of calibration.