A hyphenated technique based on the combination of high performance liquid chromatography (HPLC), electrochemical (coulometric) oxidation (EC) and electrospray ionization (ESI)- or atmospheric pressure chemical ionization (APCI)- mass spectrometry (MS), allows access of selected groups of low and medium polarity analytes to ESI- or APCI- mass spectrometry after HPLC by electrochemical treatment of the sample.