The capillary (110) has a constriction (120) provided in an opening (114), where a separation line (122) with a preset breaking point (124) and/or a separation marking is formed between the opening and another opening. The capillary includes capillary volumes such that a defined volume of a target constituent (154) of a sample (134) is less than 50 percentages of the capillary volumes. An anticoagulant coating i.e. ethylenediaminetetraacetic coating, is applied on an inner side of the capillary. The opening with the constriction is glazed and/or designed planar. An independent claim is also included for a method for providing a defined volume of a target constituent of a sample.
