An apparatus for use in a semi- automatic method for the preparation of a sample of liquid includes a test tube (10), an elongated tube or sample petter (116) of smaller diameter than the test tube and with its lower end closed, and an aspirator (or vacuum) device (42). The sample petter has an enlarged hollow chamber (118) near its closed lower end (120), and at least one opening (119) into the chamber. When the closed end of the petter tube rests on the test tube bottom, the outer periphery of the enlarged hollow chamber does not sealingly engage the internal walls of the test tube but is fairly closely spaced thereto, e.g. by 0.003"-0.006". Excess sample in the test tube is readily aspirated from above the fluid opening (119) when the aspirator device (42) is connected to the open upper end (117) of the petter tube to leave a desired reproducible volume of sample liquid below the fluid opening. The sample petter tube is then withdrawn from the test tube and released from the aspirator device by a remote push- button semi-automatic means (48). No physical contact between the technician and the petter tube is required. IMAGE
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