We recommend the gradient to be prepared just before use. This will give a better preparation with a higher yield and more motile sperm. The interface between the upper and lower gradient layers is an important physical hinder where a lot of dead or immotile sperm and debris is found. This effect also occurs between the semen sample on top of the upper gradient layer; same principle, where other
cells are removed. If the gradient is prepared several hours in advance, the layers will integrate with each other and not give the same separation.
