PerkinElmer LS 55, User Manual

Page: 50 / 202

50 . LS 55 User’s Guide
Using Stirrer Bars
Several accessories feature built-in stirring mechanisms.
It is intended that stirring is performed in a cuvette supplied by PerkinElmer. These
cuvettes are completely optically flat on all surfaces, including the base, allowing
the stirrer bar to freely rotate, whereas certain disposable cuvettes, made of
polystyrene or a similar polymer, have curved internal bases from the molding
process. This can cause severe physical disturbance of the rotation of the stirrer,
such that the stirrer cannot rotate at all or it rotates very erratically. In this case, it
is best to use a flat, round stirrer with a cross or vane built into the top. This type
of stirrer is more stable, and can rotate on an uneven surface.
PerkinElmer cuvette Polymer cuvette Special stirrer
Figure 30 Stirrers in cuvettes
The stirrer is controlled using the FL WinLab LS 55 Status application, by clicking
the accessory icon. Three speeds can be set:
•
Off
- no stirring.
•
Low
- intended for keeping sensitive cells in suspension without physical
damage.
•
High
- intended for keeping the sample suspended (or the temperature
homogeneous) where the sample will not be physically damaged by the
grinding action between the stirrer and the bottom of the cuvette.
NOTE: High speed is not intended for rapid mixing within the cuvette as stirrer
speeds high enough to effect rapid mixing often cause a vortex to be
created, producing bubbles in the light beam and high and erratic
background levels.