A method for and a device to be used when preparing a milk sample that contains a first constituent and a second constituent. The device includes a first section (1), a second section (2), a third section (3) and fourth section (4). The milk sample is centrifuged to obtain a plurality of sample parts including a first sample part of a first volume, in which first sample part the first constituent is contained, and a second sample part of a second volume, in which second sample part the second constituent is contained. A solution is provided and supplied to the device. At least one of the sample parts is removed from the milk sample. A remaining sample part and the solution are mixed to form a sample mixture in which the remaining sample part is distributed. The sample mixture is discharged from the device.
