A high-pressure liquid chromatograph equipped with an off-column calorimetric reactor was used for the determination of metallorganic compounds such as metallothioneins. The stainless-steel gel-permeation column used was first tested with ultraviolet detection of a standard protein mixture. The metallothioneins were determined by absorbance measurements at 520 nm after an off-column reaction of the metal-containing eluates with a buffered 4-(2-pyridylazo)resorcinol (PAR) solution. The eluates were also tested by flame and electrothermal atomic-absorption spectrometry; a correlation between AAS and ICP results and the peak areas of the calorimetric detection was also made. A zinc-inhibiting reagent was also added to the PAR solution in order to find the calorimetric error due to the presence of other metals such as copper or cadmium.