Editing Kinetic isotope effect (section)

==== Isotope-ratio mass spectrometry ====

High precision [[isotope-ratio mass spectrometry]] (IRMS) is another method for measuring [[kinetic fractionation]] of [[isotope]]s for natural abundance KIE measurements. Widlanski and coworkers demonstrated {{sup|34}}S KIE at natural abundance measurements for the [[hydrolysis]] of [[sulfate]] monoesters. Their observation of a large KIE suggests S-O bond cleavage is rate controlling and likely rules out an associate [[reaction mechanism]].<ref>{{cite journal | vauthors = Burlingham BT, Pratt LM, Davidson ER, Shiner VJ, Fong J, Widlanski TS | title = 34S isotope effect on sulfate ester hydrolysis: mechanistic implications | journal = Journal of the American Chemical Society | volume = 125 | issue = 43 | pages = 13036–7 | date = October 2003 | pmid = 14570471 | doi = 10.1021/ja0279747 | bibcode = 2003JAChS.12513036B }}</ref>
[[File:34S isotope effect on sulfate ester hydrolysis reaction scheme.png|none|thumb|525x525px|34S isotope effect on sulfate ester hydrolysis reaction]]

The major limitation for determining KIEs at natural abundance using IRMS is the required site selective degradation without isotopic fractionation into an analyzable small molecule, a non-trivial task.<ref name="Singleton_1995" />