Particle Counting With The Multisizer

W Coulter

Wallace Coulter

For the most complex of sizing and counting applications, Meritics recommends the Multisizer™ Series of Coulter Counters® from Beckman Coulter®. If, however, your aim is to obtain relatively simple – but quick and accurate – counts of cells or other particles, you need look no further than Beckman Coulter’s Z™ Series.

In fact it was for counting blood cells that the Coulter Principle was first developed, by Wallace H Coulter, in the late 1940s. Today it is used as the basis for over 98% of all automated cell counters.

The ‘basic’ Z1 version offers a choice between Single and Dual Threshold Models for counting cells or particles of between 1 and 120 micron in size. Single Threshold means that the operator simply sets one size and the instrument counts all items larger than, or equal to, that value. Dual Threshold divides items between three size groups: above the upper size setting; between the two size settings; below or equal to the lower size setting.

Single Threshold is perfect for obtaining very rapid, fully automated, total cell counts when cell size is relatively uniform. Dual Threshold is ideal for mixtures of cell types and sizes.

Five standard aperture sizes are available for these models, while ampoule-insertable apertures can be used when dealing with very small sample volumes.

A further model, the Z2, has been added to the series for applications requiring analysis of size distribution as well as simple counts and concentrations. Operators can choose to display the whole size distribution, as a graph, or to compare size statistics and counts between selected areas. By positioning a cursor at any chosen point on the graph, the operator can also display the cumulative number and percentage of items above and below it.

Another added benefit of the Z2 is its ability to calculate average counts and channelise the combined data from as many as ten consecutive analyses. By counting and sizing more cells, statistical confidence is increased and the shape of the averaged size distribution becomes smoother.

A Windows-based software package, AccuComp®, is available for use with the Z2 to enable quick, accurate calculation and clear presentation of sample statistics. Size distribution statistics, data archiving, size trend analysis, results overlays, averages, graphs and tables, customised reports and import/export of data are just some of the facilities included within this package.