Chromatography Forum

Hi everybody,

Could somebody help me with the bindwidth concept?
Which bindwidth is correct for a wavelenght of 280nm? How is bindwidth value going to influence on the final chromatogram?

Thanks,

It probably won't affect anything very much, within reasonable ranges. UV absorbances tend to be fairly broad peaks; probably a thing absorbing at 280nm actually has significant absorbance all the way from 250/260 to 300/310, so whether you look at a range from 265-295, or a range from 279-281 won't matter.

If you use a very very broad range, you will lose a little selectivity, and other peaks will appear in your chromatogram (things that absorb at 230 or 240nm will begin to have an effect). If you use a very, very narrow range, you are actually relying on a smaller amount of light (in a PDA, a smaller number of light-sensitive-elements) and the noise will increase slightly. I usually default to about 9nm width, but it depends on your detector.

Just to expand on Imh's explanation. Bandwidth sets the range around a given wavelength that the detector will look at and report on the chromatogram. Allowing a broader range will detect compounds that may absorb at much different wavelengths from your target to be seen.