Abstract: A micromechanical ejection pump for extracting small fluid volumes from a flowing sample fluid is provided with a substrate, and a canal for pressurized working fluid. The micromechanical ejection pump also has a canal for ejecting a fluid volume from the sample fluid. The working fluid canal runs into the extension of the sample fluid canal discharging crosswise thereto. The ejection canal connected to the sample fluid canal branches off from the working fluid canal opposite to the sample fluid canal. The working fluid canal and the ejection canal have in particular a substantially similar cross-section of 0.01-0.12 mm2, wherein the ratio of the cross-section of the sample fluid canal to the cross-section of the working fluid canal or the ejection canal is preferably between 0.2 and 0.5, more particularly between 0.3 and 0.4 and most preferably 0.35.