The invention relates to an automatic analyzer for organic elemental analysis, said analyzer comprising:lines for gaseous fluids,sample holders to be analyzed,a catalytic combustion reactor,a water adsorber,an organic compounds detector, and a logical unit for detection data processing, wherein the analyzer further comprises an automatic oxygen meter and the oxygen supply to the catalytic combustion reactor is managed by the data processing unit as a function of the stoichiometric requirement calculation and of the operating time of the oxygen meter.
