A discussion about the significance of absorbance and sample optical thickness in conventional absorption spectrometry and wavelength modulated laser absorption spectrometry:an alternative view

摘要

I must disagree with the general premise of this paper [1],that laser-based modulation techniques cannot measure absorbance in the conventional manner.In the introduction of the paper,the authors state "laser-based modulation techniques in fact do not measure exactly the same physical quantities as conventional AAS techniques do".They further state "it is neither straightforward,nor extremely convenient,to compare a technique that measure the difference between the signals 'on' and 'off resonance to an entity that is defined in terms of the logarithm of the ratio of the two intensities",and "Absorbance is not as natural for the modulated laser-based absorption techniques".These statements are inaccurate.First,all modulation techniques measure intensity,either with a photomultiplier tube or a solid state detector.Converting intensity to absorbance is a matter of signal processing.