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Troubleshooting Problems with Ghost Peaks

Possible Cause

Prevention/Solution

Ghost Peaks

Contamination in column or injector

Use only HPLC grade solvents

Flush column to remove impurities

Flush injector between analyses

Late eluting peak from the previous injection

Extend run time

A flush column with the strong mobile phase at end of each run

For gradient runs, end at a higher concentration

Contaminated water in RP HPLC

Use HPLC-grade water

Unknown interferences in the sample

Use sample clean-up (e.g. SPE)

Negative Peaks

Refractive index of solute lower than that of mobile phase (RI detector)

Use mobile phase with a lower refractive index

Reverse detector polarity to obtain positive peaks

Absorption of solute lower than absorption

of mobile phase (UV detector)

Change UV wavelength

Use mobile phase with lower UV absorption

Sample solvent and mobile phase differ in composition

Change sample solvent and dissolve

sample in mobile phase if possible

Spikes

Air bubbles in the mobile phase

Degas mobile phase

Install back pressure restrictor at detector outlet

Ensure all fittings are tight

Column stored without endcaps

Store columns with endcaps

Flush RP column with degassed methanol



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