A sample concentrating unit for concentrating analytes in a sample (1, 1', 1") by evaporation of sample solvent comprising - a sample receiving element with at least one sample receiving position (11, 11', 11", 11′′′, 11"") having an opening confined by a rim for receiving a sample (1, 1', 1") or an open sample vessel (13, 13', 13") containing a sample (1, 1', 1"), wherein the open sample vessel comprises a body with an inner space, the inner space being adapted to receive liquids, and an opening confined by a rim through which liquids can be introduced into the inner space; - a cover element for sealing the at least one sample receiving position (11, 11', 11", 11′′′, 11""), wherein the cover element and the at least one sample receiving position (11, 11', 11", 11′′′, 11"") and/or the sample vessel (13, 13', 13") are designed to leave a cavity (30, 30', 30", 30′′′, 30"") between the cover element and an upper sample surface; the sample concentrating unit further comprising - a cavity inlet (31, 31', 31", 31′′′, 31ʺʺ) connected to a gas source via a gas channel and comprising a gas-stream directing nozzle (33a, 33b, 33c, 33', 33", 33"', 33ʺʺ) for directing a stream of gas into the cavity (30, 30', 30", 30'", 30""); - a cavity outlet (32, 32', 32", 32'", 32"") connected to a vacuum pump (50, 50', 50", 50′′′, 50"") for generating negative pressure in the cavity (30, 30', 30", 30"', 30""); wherein the gas-stream directing nozzle (33a, 33b, 33c, 33', 33", 33′′′, 33"") is arranged such that the gas stream enters the cavity (30, 30', 30", 30"', 30"") in a direction parallel to a sample surface tangent plane and on the same level as the rim of the sample receiving position (11, 11', 11", 11′′′, 11"") or the rim of the sample vessel (13, 13', 13") thereby cooperating with the vacuum pump (50, 50', 50", 50′′′, 50"") to transport evaporated sample solvent out of the cavity (30, 30', 30", 30'", 30"") through the cavity outlet (32, 32', 32", 32"', 32ʺʺ), and - a controller configured to control the vacuum pump (50, 50', 50", 50"', 50"") to automatically adjust the negative pressure in the cavity (30, 30', 30", 30"', 30"") in order to maintain the sample (1, 1', 1") at boiling point until a predetermined level of sample solvent evaporation is reached. - a sample receiving element with at least one sample receiving position (11, 11', 11", 11′′′, 11"") having an opening confined by a rim for receiving a sample (1, 1', 1") or an open sample vessel (13, 13', 13") containing a sample (1, 1', 1"), wherein the open sample vessel comprises a body with an inner space, the inner space being adapted to receive liquids, and an opening confined by a rim through which liquids can be introduced into the inner space; - a cover element for sealing the at least one sample receiving position (11, 11', 11", 11′′′, 11""), wherein the cover element and the at least one sample receiving position (11, 11', 11", 11′′′, 11"") and/or the sample vessel (13, 13', 13") are designed to leave a cavity (30, 30', 30", 30′′′, 30"") between the cover element and an upper sample surface; - a cavity inlet (31, 31', 31", 31′′′, 31ʺʺ) connected to a gas source via a gas channel and comprising a gas-stream directing nozzle (33a, 33b, 33c, 33', 33", 33"', 33ʺʺ) for directing a stream of gas into the cavity (30, 30', 30", 30'", 30""); - a cavity outlet (32, 32', 32", 32'", 32"") connected to a vacuum pump (50, 50', 50", 50′′′, 50"") for generating negative pressure in the cavity (30, 30', 30", 30"', 30""); wherein the gas-stream directing nozzle (33a, 33b, 33c, 33', 33", 33′′′, 33"") is arranged such that the gas stream enters the cavity (30, 30', 30", 30"', 30"") in a direction parallel to a sample surface tangent plane and on the same level as the rim of the sample receiving position (11, 11', 11", 11′′′, 11"") or the rim of the sample vessel (13, 13', 13") thereby cooperating with the vacuum pump (50, 50', 50", 50′′′, 50"") to transport evaporated sample solvent out of the cavity (30, 30', 30", 30'", 30"") through the cavity outlet (32, 32', 32", 32"', 32ʺʺ), and - a controller configured to control the vacuum pump (50, 50', 50", 50"', 50"") to automatically adjust the negative pressure in the cavity (30, 30', 30", 30"', 30"") in order to maintain the sample (1, 1', 1") at boiling point until a predetermined level of sample solvent evaporation is reached.