The use of 2,2′-thiodiethanol in the fluorimetric determination of secondary amines with o-phthalaldehyde and 2-mercaptoethanol

The fluorimetric determination of secondary amines based on conversion with sodium hypochlorite to primary amines and the o-phthalaldehydemercaptoethanol (OPA) reagent is discussed. Interference by excess hypochlorite (e.g., oxidation of OPA or conversion of primary amines to chloramines) were suppressed by 2,2′-thiodiethanol. Two spectrophotofluorimetric method are reported, one for aromatic and the other for aliphatic secondary amines. These methods permitted determinations at nanomolar levels; relative standard deviations were 4% for 5 nmol of N-methylaniline and 13% for 5 nmol of sarcosine.