An existing method for HPLC determination of thiol-containing peptides has been successfully adapted to the analysis of mixtures of glutathione (GSH) and some related peptides with their Hg(II) complexes as a first approach to the study of phytochelatin extracts. The separation was achieved in a C18 column with a mobile phase of 0.1% trifluoroacetic acid (TFA) and 0.1% TFA/acetonitrile. Non-derivative UV-vis detection at 202 nm used in the original method has been complemented with amperometric detection at 1.2 V on glassy carbon electrode. Two different Hg(II)-GSH complexes were observed by both detection modes and confirmed by mass spectrometry.