SOME ASPECTS OF THE LUMINOL LIGHT REACTION 



H. H. Seliger 



McCollum-Pratt Institute and Department of Biology 



The Johns Hopkins University, Baltimore, Maryland 



Introduction 

 With the exception of biohiminescence, the oxidation of kmiinol 

 is the most efficient chemihnninescent reaction known and has been 

 the subject of comprehensive chemical investigations, the most re- 

 cent by White and coworkers (7) . With material purified in the 

 latter's laboratory the luminol light reaction is being investigated 

 by quantitative spectroscopic techniques and the following is a sum- 

 mary of some of the results obtained to date. 



Experiments and Discussion 



The primary object of the present investigation is to identify the 

 molecule whose excited state gives rise to the chemiluminescence. 

 This in itself requires two assumptions relative to the oxidation re- 

 action, and the validity of any conclusions reached rests on how 

 closely these assumptions hold within the general framework of 

 the mechanism of chemiluminescence. Briefly, one assumes that (I) 

 light emission o(curs from the excited state of a relatively stable 

 molecule, either the original molecule or an oxidized product; and 

 (II) the ionic environment in which the excited molecule finds 

 itself immediately after the oxidation process is not dissimilar from 

 the general ionic environment. 



In order to eliminate any possible effects of resonance self-absorp- 

 tion, the chemiluminescence emission spectrum of a highly purified 

 10-5 M luminol solution in .1 N NaOH was measured photoelec- 

 trically by a charge-normalization technique already described (5), 

 and is shown in Fig. 1 together with the fluorescence spectrum of the 

 neutral luminol molecule in acid solution. These data are similar 

 to tiic results of Spruit and Spruit van der Burg (6) , who suggest 

 that, by virtue of the coincidence of the spectra, the neutral luminol 

 molc(ulc is tiie emitting species in the light reaction. This picture 

 seems to Ik- generally accepted (1) , and the further assumption is 



200 



