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 receives 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 its 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 piston and 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 .