Agilent InfinityLab LC Series Diode Array Detectors User Manual
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Optimizing the Detector
Optimizing the Detector Regarding to the System
it is a wide band as close to the signal wavelength as possible but on a zero
absorbance region. Reference bandwidths of 60 nm to 100 nm are commonly
used. The default reference is 360 nm with a bandwidth of 100 nm. A wide
bandwidth is used because this reduces the noise in the reference signal (from
statistical theory, the error, i.e. noise in this case, is reduced by the square root of
the number of determinations). It is important that the reference bandwidth does
not extend to a part of the spectrum that has some absorbance as this would
then reduce the resulting signal and sensitivity would be reduced. The use of a
reference wavelength can help to reduce drift or wander in the chromatogram
caused by refractive index changes due to room temperature fluctuation or
gradient operation. The effect of a reference signal can be easily tested by setting
two otherwise identical signals, one with and one without a reference signal. If
there is no part of the spectrum with zero absorbance then it will be better to
have the reference signal turned off.
Figure 30 Spectrum of Anisic Acid
Peak Width, Response Time and Data Collection Rate
The peak width setting, response time and data rate in the detector are all linked.
The available settings are shown in
on page 100 and in
page 101. It is important to set this correctly for optimum sensitivity and to
preserve the resolution achieved in the separation.
The detector internally acquires data points faster than is needed for a
chromatogram and processes them to produce the signal seen by the data
system. Part of the processing reduces the data to an appropriate data rate
