Editing Superoxide (section)

===Assay in biological systems===
The assay of superoxide in biological systems is complicated by its short half-life.<ref name="pmid8074285">{{cite journal | last1 = Rapoport | first1 = R. | last2 = Hanukoglu | first2 = I. | last3 = Sklan | first3 = D. | title = A fluorimetric assay for hydrogen peroxide, suitable for NAD(P)H-dependent superoxide generating redox systems. | journal = Anal Biochem | volume = 218 | issue = 2 | pages = 309–13 |date=May 1994 | doi = 10.1006/abio.1994.1183 | pmid = 8074285 | s2cid = 40487242 | url = https://zenodo.org/record/890715}}</ref> One approach that has been used in quantitative assays converts superoxide to [[hydrogen peroxide]], which is relatively stable. Hydrogen peroxide is then assayed by a fluorimetric method.<ref name="pmid8074285" /> As a free radical, superoxide has a strong [[Electron paramagnetic resonance|EPR]] signal, and it is possible to detect superoxide directly using this method. For practical purposes, this can be achieved only in vitro under non-physiological conditions, such as high pH (which slows the spontaneous dismutation) with the enzyme [[xanthine oxidase]]. Researchers have developed a series of tool compounds termed "[[spin trap]]s" that can react with superoxide, forming a meta-stable radical ([[half-life]] 1–15 minutes), which can be more readily detected by EPR. Superoxide spin-trapping was initially carried out with [[DMPO]], but phosphorus derivatives with improved half-lives, such as [[DEPPMPO]] and [[DIPPMPO]], have become more widely used.{{citation needed|date=October 2019}}