Biotek EL800, Operator'S Manual

Page: 128 / 218

102
|
Chapter 4: Instrument Qualification
BioTek Instruments, Inc.
Recommendations for Achieving Optimum
Performance
Microplates should be perfectly clean and free of dust or bottom scratches. Use new
microplates from sealed packages. Do not allow dust to settle on the surface of the
solution; use microplate covers when not reading the plate. Filter solutions to remove
particulates that could cause erroneous readings.
Although the ELx800™ supports standard flat, U-bottom, and V-bottom microplates,
optimum performance is achieved with optically clear, flat-bottomed wells.
Nonuniformity in the optical density of the well bottoms can cause loss of accuracy,
especially with U- and V-bottom polyvinyl microplates. Check for this by reading an
empty microplate. Dual-wavelength readings can eliminate this problem, or bring the
variation in density readings to within acceptable limits for most measurements.
Inaccuracy in pipetting has a large effect on measurements, especially if smaller
volumes of liquid are used. For best results, use at least 100
μ
l per well in a 96-well
plate and 25
μ
l in a 384-well plate.
Dispensing solution into 384-well plates often traps air bubbles in the wells, which
may result in inaccurate readings. A dual-wavelength reading method usually
eliminates these inaccuracies; however, for best results, remove the air bubbles by
degassing the plate in a vacuum chamber before reading.
The inclination of the meniscus can reduce reading accuracy in some solutions,
especially with small volumes. Agitate the microplate before reading to help bring this
problem within acceptable limits. Use Tween
®
20, if possible (or some other wetting
agent) to normalize the meniscus. Some solutions develop menisci over a period of
several minutes. This effect varies with the brand of microplate and the solution
composition. As the center of the meniscus drops and shortens the light path, the
density readings change. The meniscus shape will stabilize over time.