AUTOMATIC PIPETTER

摘要

TITLE: AUTOMATIC PIPETTER INVENTOR: CHRISTIAN STAHLI An automatic pipetter utilizing a syringe having several openings at its end. A different tubing segment connects with each of these openings and extends into different vials of liquids. Of these vials, one contains a buffer solution generally used in appreciably greater quantities than the others. Another vial receive, the liquids from the syringe. As a stepping motor partially withdraws the piston from the syringe, a tube leading to a vial with unmeasured liquid is open. When the stepping motor reinserts the plunger into to the syringe, the tube leading to the receiving vial becomes open while the other tubes remain closed. The tubing segments extending between the syringe and the vials include three sections. The section closest to the syringe, formed from polyimide, undergoes a minimal change in its volume notwithstanding the negative and positive partial pressures exerted by the piston. The second section, having a plasticized polyvinyl chloride construction, has greater flexibility than the polyimide portion. Pinching off this flexible section from the outside provides a valving device for the system. The last section of the tubing consists of stainless steel and runs into the vial to provide a high degree of rigidity. Coating the inside with dimethyldichlorosilane reduces is rusting and crosscontamination between pipetted liquid. In operating the pipetter, the buffer should follow the other liquids placed into a single container. This washes the syringe between samples and avoids carry-over error from one sample to the next. After expelling fluid from the syringe, the stepping motor moves at least one step in the direction of withdrawing the piston but with the outlet open. This removes the slack in the coupling between the motor and the pistonand increases the accuracy in the volume of sample drawn into the syringe. The pipetter, when called upon to deliver a microliter of a particular liquid, will deliver from .98 to 1.02 microliters at least 90 per cent of the time.