Agilent Technologies 1100 Series Reference Manual page 40

2 How to optmize the Detector
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.
Substances with fine structures and steep slopes like benzene are very rare.
In most cases the width of absorbance bands in the spectrum is more like 30 nm as
with anisic acid (see
In most situations, a slit width of 4 nm will give the best results.
Use a narrow slit (1 or 2 nm) if you want to identify compounds with fine spectral
structures or if you need to quantify at high concentrations (> 1000 mAU) with a
wavelength at the slope of the spectrum. Signals with a wide bandwidth can be used to
reduce baseline noise. Because (digital) bandwidth is computed as average of
absorbance, there is no impact on linearity.
Use a wide (8 or 16 nm) slit when your sample contains very small concentrations.
Always use signals with bandwidth at least as wide as the slit width.
40 1100 Series DAD and MWD Reference Manual
Figure 10).