128 1220 Infinity II LC System User Manual
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Detector Description
Agilent 1220 Infinity II LC Diode Array Detector (DAD)
Figure 41 Benzene at 1, 4 and 16 nm slit width (principle)
A wide slit uses more of the light shining through the flow cell. This gives
lower baseline noise as shown in Figure 42 on page 128.
Figure 42 Influence of the Slit Width on Baseline Noise
However, with a wider slit, the spectrograph’s optical resolution (its ability to
distinguish between different wavelengths) diminishes. Any photodiode
receives light within a range of wavelength determined by the slit width. This
explains why the fine spectral structure of benzene disappears when using a
16-nm wide slit.
Furthermore, the absorbance is no longer strictly linear with concentration
for wavelengths at a steep slope of a compound’s spectrum.
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