Sub-isoforms of rabbit liver metallothionein (MT-RL) and of its two main isoforms (RL-1 and RL-2) have been readily separated at room temperature on a reverse phase column using a gradient of TFA and acetonitrile. MT samples were prepared at neutral and acidic pH. The detection was double, consisting of two UV and electrochemical (EC) detectors on line, the EC (coulometric) detection being based on the oxidation of the thiol groups into disulphides at the graphite electrode. Two types of peaks were observed, those equally detected by UV and by EC, being attributed to original thiol containing sub-isoforms and those less hydrophobic, detected by UV but hardly at all by EC, being attributed to oxidised species containing disulphides instead of thiols, hence not detectable in our EC mode. All peaks in RL could be attributed to either RL-1 or RL-2 contribution, except for one of the oxidised forms. The elutions were then carried out at various temperatures between 25 and 60C.