
Chapter 3 Preparing Samples
3-34 PerSeptive Biosystems
3
3.2.4 Examining Crystals on Sample Plates
Overview
If you are using polished blank or laser etched sample plates
(see “Types of sample plates” on page 3-29), you can look at
the crystallization of sample and matrix under a microscope. A
magnification of 30X is sufficient to see crystals.
You can also view crystallization on the video monitor on the
instrument.
The morphology of crystals is a critical element for successful
analysis. Ideally, you want small crystals that are evenly
distributed in the sample well.
α
-cyano or
sinapinic acid
Figure 3-1 illustrates good patterns of crystallization for
α
-cyano and sinapinic acid matrices.
Figure 3-1 Microscopic View of Sample Plate with
α
-Cyano or Sinapinic Acid Matrices
With good crystallization, you see small, equally-sized crystals
that are evenly distributed on the plate. Clumping is not
desirable. If you see clumped crystals with
α
-cyano or
sinapinic acid matrices, it may indicate:
• Matrix concentration is too high
• Organic concentration is too high
• Sample plate was dried too quickly
• Sample contains contaminants
PB100265
α
-cyano
Sinapinic acid
Rounded
Rhomboid-shaped
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