National Metrology Institute of Japan (NMIJ), National Institute of Advanced Industrial Science and Technology (AIST), AIST Central-3, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8563, Japan.
Biomedical Research Institute (BMRI), National Institute of Advanced Industrial Science and Technology (AIST), AIST Central-6, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8566, Japan.
Anal Chem. 2022 Sep 20;94(37):12595-12603. doi: 10.1021/acs.analchem.2c01005. Epub 2022 Sep 5.
An absolute quantitative analysis of free radicals by combining the effective magnetic moment method and the quantitative electron paramagnetic resonance [qEPR] method is proposed. This combined method utilizes the advantages of both the analytical methods and compensates for their disadvantages. In the effective magnetic moment method, the magnetic moment under a constant magnetic field is measured accurately using a superconducting quantum interference device. The qEPR method compares a "primary standard sample" and "secondary standard sample". The effective magnetic moment method was used to determine the purity of the primary standard sample. The qEPR method realizes a simple purity analysis of free-radical reagents with traceability to the International System of Units (SI). The purity of the free radicals by the qEPR method for pure 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl benzoate [4HTB], 1-oxyl-2,2,6,6-tetramethyl-4-hydroxypiperidine [TEMPOL], and di(phenyl)-(2,4,6-trinitrophenyl)iminoazanium [DPPH] reagents was obtained with a relative expanded uncertainty of 0.7% for 4HTB to 1.5% for the DPPH. These small uncertainties were almost equal to those of the purity of the primary standard samples and were achieved by adopting in-plane positioning of the measured sample perpendicular to the cylindrical axis of the sample space of the superconducting quantum interference device. Some purity values of the free radicals for these reagents differed from those stated by the manufacturers. This combined method enables short-time quality control of pure radical reagents, instead of quality control by separation analytical methods or titrations.
提出了一种将有效磁矩法和定量电子顺磁共振[qEPR]法相结合的自由基绝对定量分析方法。该组合方法利用了分析方法的优势，并弥补了它们的缺点。在有效磁矩法中，使用超导量子干涉装置准确测量恒磁场下的磁矩。qEPR 方法比较“基准标准样品”和“次级标准样品”。有效磁矩法用于确定基准标准样品的纯度。qEPR 方法实现了自由基试剂的简单纯度分析，具有与国际单位制（SI）的可追溯性。通过 qEPR 法测定纯 4-羟基-2,2,6,6-四甲基哌啶 1-氧自由基苯甲酸酯[4HTB]、1-氧自由基-2,2,6,6-四甲基-4-羟基哌啶[TEMPOL]和二（苯基）-（2,4,6-三硝基苯基）亚氨基铵[DPPH]自由基试剂的纯度，相对扩展不确定度为 0.7%，4HTB 为 1.5%，DPPH。这些小的不确定度几乎与基准标准样品的纯度不确定度相等，这是通过采用测量样品与超导量子干涉装置样品空间圆柱轴垂直的平面定位来实现的。这些试剂的一些自由基纯度值与制造商提供的值不同。该组合方法能够对纯自由基试剂进行短时间的质量控制，而不是通过分离分析方法或滴定进行质量控制。
