What does dead volume mean?

Dead volume is defined as that portion of the flow path which is not directly inline,that is, unswept. It is these small spaces within your system where remixing of the separated sample bands occur, or where the initial sample is diluted with mobile phase. Dead volume should be minimized in a system, especially when small-volume columns of high plate numbers are used. Many times, dead volume can manifest itself through poor analytical data, often seen as split peaks or broad peaks on your chromatogram.

It is important to note that “dead volume” does not typically refer to the overall internal volume of a product or system. Usually, at least some portion of the pathway through a product is directly in the flow path — this volume is typically referred to as “swept volume.” For proper reference to the total internal volume, the term “void volume” should be used.