Notes: (±)-Cotinine-d3 is intended for use as an internal standard for the quantification of cotinine by GC- or LC-MS. Cotinine is an alkaloid found in tobacco and a major metabolite of nicotine (Item No. 16535).{43471,20196} It is formed by oxidation of nicotine by the cytochrome P450 (CYP) isoform CYP2A6.{20196}