Device for preparing and injecting a sample comprising: (a) a sample preparation compartment comprising: (i) a leaktight preparation chamber having: - a means for introducing the sample, - at least one leaktight inlet and at least one leaktight outlet enabling the circulation of a flushing gas through said preparation chamber; (ii) a means of heating said preparation chamber; (iii) a means of cooling said preparation chamber; (iv) a leaktight means for introducing a liquid substance into the preparation chamber connected to at least one reservoir intended to contain a liquid substance; and (b) an injection compartment comprising: (i) a leaktight focusing chamber having at least one leaktight inlet connected to the outlet of the preparation chamber and at least one leaktight outlet enabling the circulation of said flushing gas through said chamber; (ii) a means of heating said focusing chamber; (iii) a means of cooling said focusing chamber; (c) a valve located between the outlet of the preparation chamber and the inlet of the focusing chamber; (d) means for controlling and means for monitoring the temperature of the preparation chamber and of the focusing chamber; and (e) means for controlling and means for monitoring the pressure in the preparation chamber and in the focusing chamber. (a) a sample preparation compartment comprising: (i) a leaktight preparation chamber having: - a means for introducing the sample, - at least one leaktight inlet and at least one leaktight outlet enabling the circulation of a flushing gas through said preparation chamber; (ii) a means of heating said preparation chamber; (iii) a means of cooling said preparation chamber; (iv) a leaktight means for introducing a liquid substance into the preparation chamber connected to at least one reservoir intended to contain a liquid substance; and (i) a leaktight preparation chamber having: - a means for introducing the sample, - at least one leaktight inlet and at least one leaktight outlet enabling the circulation of a flushing gas through said preparation chamber; - a means for introducing the sample, - at least one leaktight inlet and at least one leaktight outlet enabling the circulation of a flushing gas through said preparation chamber; (ii) a means of heating said preparation chamber; (iii) a means of cooling said preparation chamber; (iv) a leaktight means for introducing a liquid substance into the preparation chamber connected to at least one reservoir intended to contain a liquid substance; and (b) an injection compartment comprising: (i) a leaktight focusing chamber having at least one leaktight inlet connected to the outlet of the preparation chamber and at least one leaktight outlet enabling the circulation of said flushing gas through said chamber; (ii) a means of heating said focusing chamber; (iii) a means of cooling said focusing chamber; (i) a leaktight focusing chamber having at least one leaktight inlet connected to the outlet of the preparation chamber and at least one leaktight outlet enabling the circulation of said flushing gas through said chamber; (ii) a means of heating said focusing chamber; (iii) a means of cooling said focusing chamber; (c) a valve located between the outlet of the preparation chamber and the inlet of the focusing chamber; (d) means for controlling and means for monitoring the temperature of the preparation chamber and of the focusing chamber; and (e) means for controlling and means for monitoring the pressure in the preparation chamber and in the focusing chamber.