Separation of monocytes from a leukocyte-rich plasma by flotation through a discontinuous iodixanol gradient
The monocytes in human peripheral blood, account for, on average, about 8% of the leukocyte population. They tend to be larger (15-20 µm) than lymphocytes (6-20 µm) and they also have a slightly lower density (Figure 1).
These properties allow some scope for their separation by centrifugation. Boyum  introduced a Nycodenz® density barrier (ρ = 1.068 g/ml) for resolving monocytes and lymphocytes from a leukocyte-rich plasma. This is commercially available as Nycoprep™ 1.068.
a slightly raised osmolality (335 mOsm); this
enhances the density difference between the
monocytes and the osmotically-sensitive
lymphocytes, whose density is increased. The
method is very effective and the purity of the
monocytes is greater than 90% but the monocytes do
not form a distinct band; they are concentrated in the
upper half of a broad turbid zone within the