Columns | Column: LC Troubleshooting

The potential causes are considered for peak distortion for the first two peaks in the chromatogram.The potential causes are considered for peak distortion for the first two peaks in the chromatogram.

Readers' questions regarding problems related to internal standard calibration of liquid chromatography methods are addressed.

Recently, I received an inquiry from a reader regarding a problem he encountered with a routine liquid chromatography (LC) method in his clinical laboratory.

When converting methods from liquid chromatography (LC) to ultrahigh-pressure liquid chromatography (UHPLC), don't get confused by flow-rate settings.

One of the most frequent times that we discover a problem with a liquid chromatography (LC) method is when we examine a data set following the analysis of a batch of samples.

Why are liquid chromatography retention times sometimes so slow to stabilize?

Have a problem with your LC system? Maybe applying a little "DDT (Don't Do That)" 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 can you avoid phase collapse when 5% organic solvent is too strong?

How can internal LC surfaces be made less reactive?

Stainless steel is inert – or is it?

A scouting gradient is a separation run under a standardized set of conditions and can be used to determine the complexity of a sample and estimate the difficulty of the separation. John Dolan tells why he believes using a scouting gradient is the best way to begin method development.

After exploiting the chemical factors in the separation process, chromatographers can adjust column conditions – flow rate, column size, and particle diameter – to further improve separations.

In part III of this column series, John Dolan demonstrated that systematic variation of the solvent strength can change selectivity and retention, and changing solvent type can amplify the effect. This month, he looks at three additional parameters (pH, temperature, and column type) for adjusting selectivity.

Most chromatographers can look at a chromatogram and provide a qualitative opinion about the separation, but it is equally important to be able to measure the separation quality.

LC problems fall into one of two categories: those associated with instrumentation and those associated with the separation itself. Dolan explains how to identify which kind you have and how to approach correcting the problem.

Readers submit questions about how to isolate the source of carryover in LC methods, mobile-phase temperature effects, and the care of cleaning of columns.

Inadequate mobile-phase gassing may be the single largest cause of LC problems. Columnist Dolan examines bubble-problem sources and techniques that analysts can use to eliminate excess gas in the mobile phase.

Peak shape problems don't always have a single solution.