
Appendix H Continuous Extraction Mode
H-8 PerSeptive Biosystems
H
H.2 Obtaining Good Spectra
in Continuous Extraction Mode
This section describes:
• Spectra, resolution, signal-to-noise ratio, and laser
threshold
• Determining laser threshold
• Checking Resolution
• Fine-Tuning the Laser Setting
H.2.1 Spectra, Resolution, Signal-to-Noise
Ratio, and Laser Threshold
What is a good
spectrum?
A good spectrum is one that is acceptable for your purposes.
In general, it:
• Contains sharp, symmetrical, well-defined peaks
• Has acceptable resolution
• Has acceptable signal-to-noise ratio
For some applications (for example, when you are looking for
detailed structural information), you may require very
well-separated peaks and the maximum resolution possible.
For other applications (for example, when looking for an
estimate of molecular weight), your requirements may be less
strict.
Resolution and
signal-to-noise
ratio
There is a balance between good resolution and a good
signal-to-noise ratio. To achieve maximum resolution, you may
a see lower signal-to-noise ratio. Conversely, to maximize the
signal-to-noise ratio, you may see less than maximum
resolution.
Figure H-1 through Figure H-4 are examples of poor and good
spectra.
NOTE: Dimer in a spectrum may indicate that the molecular
ion is saturated, or that sample is too concentrated.
Decrease laser intensity or sample concentration to
minimize the dimer.
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