Clarification of plasma from whole human blood using ultrasound

There has been interest for a number of years in the possibility of separating blood into cells and plasma by methods other than centrifugation, so that the plasma can be analysed on-line. Cells in whole blood normally occupy about 45% of the suspension volume. It has been shown with a number of different cell types, such as yeast and bacteria, that for concentrations of this order the cells are not as efficiently harvested by ultrasound as those for lower concentrations. In this study, removal of cells from 3-4 ml whole blood volumes has been examined in ultrasonic standing wave fields from tubular transducers driven at a frequency of 1.6 MHz. Samples of whole human blood (n = 11) from two volunteers have been processed by three tubular transducers where high levels of cell removal, 99.7% on average, have been demonstrated with high reproducibility between samples as well as for different transducers.