著者

Nobuhiro MATSUMOTO Nobuyasu ITOH

出版者

The Japan Society for Analytical Chemistry

雑誌

Analytical Sciences (ISSN:09106340)

巻号頁・発行日

vol.34, no.8, pp.965-971, 2018-08-10 (Released:2018-08-10)

参考文献数

53

被引用文献数

6

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Di(phenyl)-(2,4,6-trinitrophenyl)iminoazanium [DPPH] is widely used as a standard for measuring the number of free radicals. Here, we evaluated the number of free radicals of “DPPH” reagents from three manufacturers by effective magnetic moment method. Interestingly, the reagents from different manufacturers had varying temperature dependencies for both magnetic moment and g-value at low temperatures. As a result, the maximum relative difference among the three reagents on the number of free radicals per unit mass was 20%. Carbon hydrogen nitrogen (CHN) analyses, high-resolution EPR measurements, FT-IR measurement, and NMR measurement confirmed that a major component of only one among the three reagents was “pure” DPPH. The evaluated purity based on free radical content was 0.998 kg kg−1 with expanded uncertainty of 0.036 kg kg−1. The other two reagents were found to be contaminated by several % of benzene in the DPPH crystal structure.