124 Agilent InfinityLab LC Series 1260 Infinity II FLD User Manual
5
Optimizing the Detector
Finding the Best Signal Amplification
Finding the Best Signal Amplification
Increasing the PMTGAIN increases the signal and the noise. Up to a certain
factor the increase in signal is higher than the increase in noise.
The step from gain to gain is equal to a factor of 2.
In Figure 46 on page 124 the PMTGAIN was gradually raised from 4 up to 11
(the peak is from the Agilent Technologies isocratic sample which was diluted
1000 times). With increasing PMTGAIN there was an improvement in
signal-to-noise up to 10. Above 10 the noise increased proportionately to the
signal with no improvement in signal-to-noise.
Figure 46 Finding Best PMTGAIN for Biphenyl
The reason for this is the fact, that quantification of baselines (especially at
low background levels) is not sufficient for statistically working filter
methods. For the best gain, check your solvent under flow conditions with the
auto-gain function. Do not use higher values than proposed by the system, if
not necessary, because of excessive high fluorescence signals.
Use the PMT test to automatically determine the setting.
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