Method for automated in vitro detection and/or quantification of analytes contained in samples, comprising the following steps: - placing the sample in a situation to react with one or more reagents to directly or indirectly produce a reaction solution comprising, in the presence of an analyte determined in the sample, an optical agent having at least one predetermined optical property; - illuminating the reaction solution contained in an optical analysis zone with an incident electromagnetic radiation; - detecting the optical response of the reaction solution; - deducing from the optical response the presence and/or the quantification of the analyte; the method implementing one or more reagents to directly or indirectly produce a reaction solution comprising at least two distinct optical agents each having at least one predetermined optical property, the two predetermined optical properties being distinct, the method further comprising the steps of: - acquiring a chromatic spectral decomposition of the optical response and - separately detecting the two distinct predetermined optical properties in said spectral decomposition the method being characterized in that it comprises: - a step of guiding a part of the incident electromagnetic radiation, without passing through the optical analysis zone, - a step consisting in acquiring a chromatic spectral decomposition of said part of the incident radiation, - before the step consisting in acquiring a chromatic spectral decomposition of the incident electromagnetic radiation, a step of mixing said part of the incident electromagnetic radiation and the optical response of the reaction solution, - a step of detecting the intensity of the spectrally decomposed part of the incident electromagnetic radiation. - placing the sample in a situation to react with one or more reagents to directly or indirectly produce a reaction solution comprising, in the presence of an analyte determined in the sample, an optical agent having at least one predetermined optical property; - illuminating the reaction solution contained in an optical analysis zone with an incident electromagnetic radiation; - detecting the optical response of the reaction solution; - deducing from the optical response the presence and/or the quantification of the analyte; the method implementing one or more reagents to directly or indirectly produce a reaction solution comprising at least two distinct optical agents each having at least one predetermined optical property, the two predetermined optical properties being distinct, the method further comprising the steps of: - acquiring a chromatic spectral decomposition of the optical response and - separately detecting the two distinct predetermined optical properties in said spectral decomposition - acquiring a chromatic spectral decomposition of the optical response and - separately detecting the two distinct predetermined optical properties in said spectral decomposition the method being characterized in that it comprises: - a step of guiding a part of the incident electromagnetic radiation, without passing through the optical analysis zone, - a step consisting in acquiring a chromatic spectral decomposition of said part of the incident radiation, - before the step consisting in acquiring a chromatic spectral decomposition of the incident electromagnetic radiation, a step of mixing said part of the incident electromagnetic radiation and the optical response of the reaction solution, - a step of detecting the intensity of the spectrally decomposed part of the incident electromagnetic radiation. - a step of guiding a part of the incident electromagnetic radiation, without passing through the optical analysis zone, - a step consisting in acquiring a chromatic spectral decomposition of said part of the incident radiation, - before the step consisting in acquiring a chromatic spectral decomposition of the incident electromagnetic radiation, a step of mixing said part of the incident electromagnetic radiation and the optical response of the reaction solution, - a step of detecting the intensity of the spectrally decomposed part of the incident electromagnetic radiation.