Capillary electrophoresis coupled to mass spectrometry (CE-MS) was used for the analysis of naphthenic acid fraction compounds (NAFCs) of oil sands process-affected water (OSPW).A standard mixture of amine-derivatized naphthenic acids is injected directly onto the CE column and analyzed by CE-MS in less than 15 min.Time of flight MS analysis (TOFMS),optimized for high molecular weight ions,showed NAFCs between 250 and 800 m/z.With a quadrupole mass analyzer,only low-molecular weight NAFCs (between 100 and 450 m/z) are visible under our experimental conditions.Derivatization of NAFCs consisted of two-step amidation reactions mediated by 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC),or mediated by a mixture of EDC and N-hydroxysuccinimide,in dethyl sulfoxide,dichloromethane or ethyl acetate.The optimum background electrolyte composition was determined to be 30％ (V/V) methanol in water and 2％ (V/V) formic acid.NAFCs extracted from OSPW in the Athabasca oil sands region were used to demonstrate the feasibility of CE-MS for the analysis of NAFCs in environmental samples,showing that the labeled naphthenic acids are in the mass range of 350 to 1500 m/z.