Abstract: A method for operating a dosing device comprising a control unit, a dosing unit with a cannula of a first volume, and a sampling container connected to the cannula. The method comprises moving the dosing unit in a first direction along an axis to move the cannula into a vessel containing a liquid; constantly aspirating fluid through the cannula with a predetermined volumetric flow; measuring at least one optical parameter of the aspirated fluid; when a change of the optical parameter is detected, storing a first position of the dosing unit on the axis and interrupting the movement of the dosing unit; and calculating a second position of the dosing unit on the axis at which the tip of the cannula has penetrated a first phase boundary upon immersion into the liquid. The calculation is performed on the basis of the first position, the predetermined speed, the first volume and the predetermined volumetric flow.

Abstract: The present application relates to a method for operating a dosing device with a control unit and a dosing unit. The dosing unit has a cannula with a first volume and a tip, and also a sampling container fluidically connected to the cannula. In a first step, the dosing unit is moved linearly at a predetermined speed in a first direction along an axis, such that the cannula is moved into a vessel containing at least one liquid. At the same time, fluid is aspirated constantly through the cannula with a predetermined volumetric flow by a pump device. At least one optical parameter of the aspirated fluid is measured by at least one optical sensor, which is arranged between the cannula and the sampling container. When a change of the at least one optical parameter is detected, a first position of the dosing unit on the axis is stored by the control unit and the movement of the dosing unit is interrupted.