Showing papers on "DPPH published in 1971"
TL;DR: At higher enzyme levels the essential intermediate is formed more rapidly but is removed by the promoting agents leading to overall inhibition of IAA degradation, apparently accelerated at both high and low enzyme concentrations.
20 citations
TL;DR: In this article, the authors show that 2,2-Diphenyl-1-picrylhydrazyl (DPPH) is reversibly adsorbed at acidic centers on the surfaces of a variety of common mineral pigments and fillers.
Abstract: 2,2-Diphenyl-1-picrylhydrazyl (DPPH) is reversibly adsorbed at acidic centers on the surfaces of a variety of common mineral pigments and fillers, and undergoes a subsequent irreversible reaction with adsorbed water or surface hydroxy groups to yield 1,1-diphenyl-2-picrylhydrazine, 1-(4′-nitrophenyl)-1-phenyl-2-picrylhydrazine, and 4,4′-oxybis[N-(4-picryliminocyclohexa-2,5-dienylidene)aniline] as the major products. The rate of the irreversible reaction on kaolinite is second-order with respect to DPPH and probably depends on the disproportionation between a DPPH and a protonated DPPH molecule. The possible use of DPPH as a probe for the activity of mineral fillers in polymer chemistry, and some implications on its use as a diagnostic test for radical species are discussed.
4 citations
TL;DR: It was shown that the determination of pyrogallol and 2,6-dimethoxyphenol was more accurate when absolute ethanol was used than with 95 % ethanol, and the best results were obtained when the ratio of phenol to interferent was no greater than 1:1.
3 citations