Spectral bandwidth is an important specification for UV- Vis spectrophotometers. Here you can learn why.
Spectral bandwidth (SBW) is defined as the width, at half the maximum intensity, of the band of light leaving the monochromator.
Spectral bandwidth of a spectrophotometer is related to the physical slit-width and optical dispersion of the monochromator system. In general, it is the range of colors the spectrophotometer can transmit through the test sample.
The narrower the bandwidth, the greater resolution will be achieved in measurements and scans improving peak separation and identification and the lower signal- to-noise ratio.
The accuracy of any measured absorbance depends on the ratio of the spectral bandwidth to the natural bandwidth (NBW) of the absorbing substance. The natural bandwidth is the width of the sample absorption band at half the absorption maximum. An SBW/NBW ratio of 0.1 or less will yield an absorbance measurement with accuracy 99.5% or better.