Diode array detector geometry

Such effects principally cannot be observed in multi band detectors such as a UV diode array detector or a Fourier transform infrared (FTIR) detector because all wavelengths are measured under the same geometry. For all other types of detectors, in principle, it is not possible to totally remove these effects of the laminar flow. Experiments and theoretical calculations show (8) that these disturbances can only be diminished by lowering the concentration gradient per volume unit in the effluent, which means that larger column diameters are essential for multiple detection or that narrow-bore columns are unsuitable for detector combinations. Disregarding these limitations can lead to serious misinterpretations of GPC results of multiple detector measurements. Such effects are a justification for thick columns of 8-10 mm diameter. 

An example of a solid state detector is the Reticon self-scanning photodiode array, which was specifically designed for spectroscopic applications [104]. These diode arrays contain 512 or 1024 silicon diode sensor elements on 25 jum centers corresponding to a density of 40 diodes mm" . Each diode is 2.5 mm high giving each element a slit-like geometry with a 100 1 aspect ratio. Beam registration problems do not apply to the diode array since the channel dimensions are defined by a photomask and hence the detector element size and position are completely reproducible. Solid state detectors do not suffer from lag [105] and althou they will bloom, the effect is much less severe than in a vidicon. 

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