Peptides from a sample that are not captured during the loading step
The stationary phase used in our columns has a lower retentivity of peptides than other stationary phases (peptides are eluted at a lower %ACN than other stationary phases).
Therefore, there is a small amount of peptides that will not bind to the stationary phase, even under no or low %ACN conditions. Generally, the percentage of unbound peptides represents a small percentage of the peptides from the sample.
The amount of peptides that escape capture during loading can be minimised by loading at 0% or 1% ACN.