System peaks and their impact in liquid chromatography

• Analyte peaks are distorted when eluted together with large system peaks.
• System peaks can be used for advantageous analyte peak compression.
• Unwanted system peak deformations can be avoided by system design.
• Preparative separations can have extreme band deformations due to system peaks.
• System peaks can be used for more efficient preparative separations.

A sample injected into a chromatographic system can generate extra peaks, called “system peaks”, which in general are undetectable. However, for small analytical injections, solute zones eluting with a system zone will often give strongly deformed solute peaks. But, if a solute zone is eluted in a particular region of the system zone it will instead be strongly compressed and well-shaped. For overloaded solute injections, another type of complex band deformation may take place due to large system peaks. This review will present results related to system peak distortions of both small analytical peaks and large preparative ones. Guidelines will be given on how to avoid unwanted distortions and how to utilize the distortions for increased detectability in analytical chromatography, or enhanced production rate in preparative chromatography. The works reviewed here were mainly made by Georges Guiochon, and some of his close colleagues, and is dedicated to his memory.