Analytical method for oxygen analysis in an oxidizable compound or in a mixture of oxidizable compounds, said oxidizable compound(s) being organic compound(s), comprising: (a) providing a test sample containing, or consisting of, at least one oxidizable compound, and a reference sample containing, or consisting of, at least one oxidizable reference compound which contains at least one chemical element present in the test sample, (b) submitting separately the test sample and the reference sample to the following steps under the same conditions: (i) a step of complete oxidative reaction, in which the sample is submitted to an oxidizing medium containing at least one oxidizing agent under conditions efficient to completely oxidize the sample into gaseous oxidized species A a O o, where A is any chemical element different from O present in the sample, a is the number of A atoms, o is the number of O atoms, said oxidizing medium containing a predetermined content of an isotope of oxygen Z O that is not the same as natural composition and distribution of oxygen isotopes, where z is the mass number of the atom, (ii) a step of detection, in which all the gaseous oxidized species A a O o, or some predetermined gaseous oxidized species A a O o, formed in step (i) are detected by means of a detector device adapted to detect gaseous oxidized species containing different isotopes of oxygen and to generate, for each detected gaseous species, a signal representative of the quantity of said detected gaseous species, the signals obtained for the test sample and for the reference sample being further treated and compared for at least one action chosen from determination of the presence of oxygen and quantification of oxygen. (a) providing a test sample containing, or consisting of, at least one oxidizable compound, and a reference sample containing, or consisting of, at least one oxidizable reference compound which contains at least one chemical element present in the test sample, (b) submitting separately the test sample and the reference sample to the following steps under the same conditions: (i) a step of complete oxidative reaction, in which the sample is submitted to an oxidizing medium containing at least one oxidizing agent under conditions efficient to completely oxidize the sample into gaseous oxidized species A a O o, where A is any chemical element different from O present in the sample, a is the number of A atoms, o is the number of O atoms, said oxidizing medium containing a predetermined content of an isotope of oxygen Z O that is not the same as natural composition and distribution of oxygen isotopes, where z is the mass number of the atom, (ii) a step of detection, in which all the gaseous oxidized species A a O o, or some predetermined gaseous oxidized species A a O o, formed in step (i) are detected by means of a detector device adapted to detect gaseous oxidized species containing different isotopes of oxygen and to generate, for each detected gaseous species, a signal representative of the quantity of said detected gaseous species, the signals obtained for the test sample and for the reference sample being further treated and compared for at least one action chosen from determination of the presence of oxygen and quantification of oxygen. (i) a step of complete oxidative reaction, in which the sample is submitted to an oxidizing medium containing at least one oxidizing agent under conditions efficient to completely oxidize the sample into gaseous oxidized species A a O o, where A is any chemical element different from O present in the sample, a is the number of A atoms, o is the number of O atoms, said oxidizing medium containing a predetermined content of an isotope of oxygen Z O that is not the same as natural composition and distribution of oxygen isotopes, where z is the mass number of the atom, (ii) a step of detection, in which all the gaseous oxidized species A a O o, or some predetermined gaseous oxidized species A a O o, formed in step (i) are detected by means of a detector device adapted to detect gaseous oxidized species containing different isotopes of oxygen and to generate, for each detected gaseous species, a signal representative of the quantity of said detected gaseous species, the signals obtained for the test sample and for the reference sample being further treated and compared for at least one action chosen from determination of the presence of oxygen and quantification of oxygen.