The cobalt content in catalyst precursors obtained by co-precipitation containing oxide forms of Co and Ce or Co and La was determined by thermal analysis coupled with mass spectrometry. The described methodology is based on two types of thermogravimetric measurements: in an inert atmosphere (TG-MS(Ar)) which allowed us to determine the content of Co3O4 and in a reducing atmosphere (TG-MS(H-2)) which specifies the metallic cobalt content in the samples. The effective determination of the active phase (Co) content in the cobalt-cerium catalyst precursor (Co/Ce) is possible by providing only one of the described measurements: TG-MS(Ar) or TG-MS(H-2). The cobalt-lanthanum material (Co/La) requires combining both measurements. Results were validated by a comparison with the results of ICP-OES analysis and demonstrated good accuracy. The phase composition of the samples was confirmed by XRPD. (C) 2014 Elsevier B.V. All rights reserved.