A method of supercritical fluide or liquid chromatography of a product P, said method comprising continuously and in this order: - an analytical step (10, 30) according to an analytical route comprising: • an operation (102, 302) of first pumping of a supercritical fluid or liquid and second pumping a modifier, • an injection operation (103, 303) of at least one sample of product P or at least one constituent of product P into at least one chromatography column, the product P or the constituent of product P being eluted with the supercritical fluid or liquid and the modifier, • an operation for separation (104, 304) of the constituents of product P, • an operation for detection (105, 305) of the composition of product P or the constituents of product P, - a switching step (X1, X2) comprising • a verification operation comprising a sub-step of comparing the analysis results with each other or with reference values representing optimal analysis conditions, and • an operation of automatic route changing (402, 502) between the analytical route and a preparative route depending on the previous comparison, - if the preparative route is selected in the switching step, a preparative step according to the preparative route comprising: • an operation of first pumping of a supercritical fluid or liquid and second pumping of a modifier, • an injection operation of at least one sample of product P into at least one chromatography column, the product P being eluted in the chromatography column by the supercritical fluid or liquid, and the modifier, • a separation operation of the constituents of product P, • a detection operation of the constituents of product P, • a collection operation of one or more constituents of product P, in an open bed, at atmospheric pressure, • a recycling operation of the supercritical fluid, said fluid being isolated from the external environment, by a switched valve once the collection operation of the preparative step has been completed. - an analytical step (10, 30) according to an analytical route comprising: • an operation (102, 302) of first pumping of a supercritical fluid or liquid and second pumping a modifier, • an injection operation (103, 303) of at least one sample of product P or at least one constituent of product P into at least one chromatography column, the product P or the constituent of product P being eluted with the supercritical fluid or liquid and the modifier, • an operation for separation (104, 304) of the constituents of product P, • an operation for detection (105, 305) of the composition of product P or the constituents of product P, • an operation (102, 302) of first pumping of a supercritical fluid or liquid and second pumping a modifier, • an injection operation (103, 303) of at least one sample of product P or at least one constituent of product P into at least one chromatography column, the product P or the constituent of product P being eluted with the supercritical fluid or liquid and the modifier, • an operation for separation (104, 304) of the constituents of product P, • an operation for detection (105, 305) of the composition of product P or the constituents of product P, - a switching step (X1, X2) comprising • a verification operation comprising a sub-step of comparing the analysis results with each other or with reference values representing optimal analysis conditions, and • an operation of automatic route changing (402, 502) between the analytical route and a preparative route depending on the previous comparison, • a verification operation comprising a sub-step of comparing the analysis results with each other or with reference values representing optimal analysis conditions, and • an operation of automatic route changing (402, 502) between the analytical route and a preparative route depending on the previous comparison, - if the preparative route is selected in the switching step, a preparative step according to the preparative route comprising: • an operation of first pumping of a supercritical fluid or liquid and second pumping of a modifier, • an injection operation of at least one sample of product P into at least one chromatography column, the product P being eluted in the chromatography column by the supercritical fluid or liquid, and the modifier, • a separation operation of the constituents of product P, • a detection operation of the constituents of product P, • a collection operation of one or more constituents of product P, in an open bed, at atmospheric pressure, • a recycling operation of the supercritical fluid, said fluid being isolated from the external environment, by a switched valve once the collection operation of the preparative step has been completed. • an operation of first pumping of a supercritical fluid or liquid and second pumping of a modifier, • an injection operation of at least one sample of product P into at least one chromatography column, the product P being eluted in the chromatography column by the supercritical fluid or liquid, and the modifier, • a separation operation of the constituents of product P, • a detection operation of the constituents of product P, • a collection operation of one or more constituents of product P, in an open bed, at atmospheric pressure, • a recycling operation of the supercritical fluid, said fluid being isolated from the external environment, by a switched valve once the collection operation of the preparative step has been completed.