So, what happens to stray light when we place any sample in the instrument for measurement? If the sample has any absorbance it has the ability to block the stray light in that absorbance wavelength range. Thus, the sample becomes its own stray light filter (blocker). So, samples, depending on how broad in wavelength their absorbance is, can frequently allow high absorbance measurements that appear to exceed the stray light specification of the instrument.

These are other unique samples that have a high absorbance level across an extend wavelength range very much like a high absorbance neutral density filter. These samples have the unique property of acting as their own stray light filter over the entire wavelength range. These samples are the darlings of instrument vendors to show 10 absorbance or even higher. Be warned, not many samples have this type of absorbance profile. So, if your sample has several absorbance peaks and returns to a low absorbance baseline in between, don’t expect to be measuring 8 plus absorbance values.

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