Clinical Chemistry, Vol 18, 771-774, Copyright © 1972 by the American Association for Clinical Chemistry

Mechanized, Direct Digital-Control Pipette for Automation of Ultramicro Chemcial Analyses

¹ Clinical Pathology Department, Clinical Center, National Institutes of Health, Bethesda, Md. 20014.

A basic direct digital-control(DDC) pipette has been developed for the automation of ultramicro chemical analysis. The new pipette is an electromechanical device, which consists of an electronic preset-indexer, a stepping motor, a screw slide assembly, a syringe barrel equipped with a dedicated displacement rod of uniform diameter. The fluid volume is measured in relation to length of the displacement rod. With the DDC pipette, one has the unique ability to control electromechanically the movement of the displacement rod in precise increments of 3.17 µm. To measure a specific volume of fluid, the number of incremental movements required by the displacement rod to equal the desired volume is dialed into decade dials. Precision studies showed that the DDC pipette was capable of measuring 1 µl of fluid with a precision better than 0.5%. With slight modifications, the basic DDC pipette can be converted into an automatic sample-diluting system.