The colour obtained upon the addition of diazosulphanilic acid to histidine in alkaline medium (Pauly reaction) is bleached rather suddenly after a certain lag. This lag is shorter the more oxygen is present in the alkaline reaction medium. A method of determining histidine on a micro scale, consisting of an improved Pauly reaction after paperchromatographic separation, is described in detail.
Sluyterman, L. A. A. E. (1960). Effect of oxygen upon the microdetermination of histidine with the aid of the Pauly reaction. Biochimica et Biophysica Acta, 38, 218-221. https://doi.org/10.1016/0006-3002(60)91234-8