Editing Kinetic isotope effect (section)

==== Compensating for variations in {{sup|13}}C natural abundance ====
Often, the largest source of error in a study that depends on the natural abundance of carbon is the slight variation in natural {{sup|13}}C abundance itself. Such variations arise; because the starting materials in the reaction, are themselves products of other reactions that have KIEs and thus isotopically enrich the products. To compensate for this error when NMR spectroscopy is used to determine the KIE, the following guidelines have been proposed:<ref name=Jankowski />
* Choose a carbon that is remote from the reaction center that will serve as a reference and assume it does not have a KIE in the reaction.
* In the starting material that has not undergone any reaction, determine the ratios of the other carbon NMR peak integrals to that of the reference carbon.
* Obtain the same ratios for the carbons in a sample of the starting material after it has undergone some reaction.
* The ratios of the latter ratios to the former ratios yields R/R{{sub|0}}.
If these as well as some other precautions listed by Jankowski are followed, KIEs with precisions of three decimal places can be achieved.<ref name=Jankowski />