Agilent InfinityLab LC Series Diode Array Detectors User Manual
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Optimizing the Detector
Optimizing for Sensitivity, Selectivity, Linearity and Dispersion
Peak width (response time)
Response time describes how fast the detector signal follows a sudden change
of absorbance in the flow cell. The detector uses digital filters to adapt response
time to the width of the peaks in your chromatogram. These filters do not affect
peak area nor peak symmetry. When set correctly, such filters reduce baseline
noise significantly (
on page 85), but reduce peak height only slightly. In
addition, these filters reduce the data rate to allow optimum integration and
display of your peaks and to minimize disk space required to store
chromatograms and spectra.
Figure 22 Influence of Response Time on Signal and Noise
on page 86 and
on page 86 list the filter choices of the
detector. To get optimum results, set peak width as close as possible to a narrow
peak of interest in your chromatogram. Response time will then be
approximately 1/3 of the peak width, resulting in less than 5 % peak-height
reduction and less than 5 % additional peak dispersion. Decreasing the peak
width setting in the detector will result in less than 5 % gain in peak height but
baseline noise will increase by a factor of 1.4 for a factor of 2 response-time
reduction. Increasing the peak width (response time) by a factor of two from the
recommended setting (over-filtering) will reduce peak height by about 20 % and
reduce baseline noise by a factor of 1.4. This gives you the best possible
signal-to-noise ratio, but may affect peak resolution.
Response time = 2 s
Response time = 0.016 s
Slit width = 4 nm
