Organic chloramine analysis and free chlorine quantification by electrospray and atmospheric pressure chemical ionization tandem mass spectrometry

Atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI), together with tandem mass spectrometry (MSn), are used to study the mechanism of chlorination of amines and to develop a method for qualitativ e and quantitative determination of organic chloramines. Cyclohexylamine an d 1,4-butanediamine (putrescine) are used as model compounds to investigate the mechanisms of the reactions between primary aliphatic amines and hypoc hlorous acid (aqueous Cl-2). The chlorination products are identified and c haracterized by collision-induced dissociation (CID) and H/D exchange. Chlo rination occurs by electrophilic addition of CI+ and may be followed by HCl elimination, hydrolysis, or, in the case of diamines, amine elimination by intramolecular nucleophilic substitution. The relative rates of chlorinati on at amine and chloramine nitrogens are a function of pH and depend on the basicity of the amine. A novel method for active chlorine quantification u sing ESI or APCI mass spectrometry is suggested on the basis of the extent of chlorination of a sacrifical amine standard. This measurement has a limi t of detection for N-chlorocyclohexylamine in the range of 0.1-10 muM, a li near dynamic range of 10(2)-10(3), and an accuracy of +/- 10%, as determine d for wastewater samples.