Implications of dispersion in connecting capillaries for separation systems involving post-column flow splitting

•Post-column flow splitting is commonly used for coupling fast LC analyses to MS.•Flow splitting can lead to very small volumetric variance peaks in the detector.•A framework is developed to help choose connecting capillaries when using splitting.•At high split ratio the capillary has a large effect even for larger volume columns.•Narrow capillaries are advised for high split ratios to avoid losses in efficiency.