A centrifugal assembly is provided that can be used in common laboratory fixed angle or swinging bucket centrifuges for the separation of material, such as parasitic ova, based on particle density. The centrifugal assembly allows the fluid level to be gently adjusted to form a meniscus without disruption of the buoyant matter, such as ova. The centrifugal assembly also enables a user to easily and hygienically collect and transfer a measured amount of a sample, such as fecal material, and to break apart and mix the sample with a floatation fluid contained in a centrifuge tube.