Mean effective wavelength

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. 

The earlier discussion (7.3) leads one to expect absorption and enhancement effects in these high-temperature alloys. For example, the results for nickel will be very sensitive to the iron content. Nickel Ka has a wavelength about 0.1 A shorter than that of the iron K edge (Figure 7-2), and a slight increase in the iron content consequently means an increased absorption of nickel Ka, which tends to reduce the apparent nickel content (negative absorption effect). Furthermore, this increased absorption of nickel Ka will enhance iron Ka, whence an... 

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