Waters 2998, Operator'S Manual

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Resolving spectral data 1-5
prevents light rays from striking the internal walls of the flow cell. The
Waters TaperSlit flow cell, so-called because of the shape of the flow cell exit
face, matches the shape of the spectrograph slit. Compared to a conventional
flow cell with a cylindrical shape, the 2998 detector achieves higher light
throughput for a given spectral resolution with the TaperSlit cell design.
Comparison of flow cell characteristics
Resolving spectral data
Together with photodiode spacing, the detector’s 50-µm slit determines the
intensity and bandwidth of the light that strikes the photodiode array.
Reducing the bandwidth increases the resolving power of the detector. As a
result, similar spectra are more effectively distinguished.
The grating images the slit onto the photodiode array. The angle of diffraction
from the grating determines the wavelength that strikes a particular
photodiode in the array.
The following figure shows an absorbance spectrum of benzene. Note that the
wavelength resolution is sufficient to resolve five principal absorption peaks.
Window
Window
UV light
Conventional flow cell:
TaperSlit analytical flow cell:
Window
Lens
UV light