PIPETTE DEVICE FOR PREVENTING CONTAMINATION CAUSED BY AEROSOL AND EXCESSIVE SUCTION

PURPOSE: To prevent contamination by aerosols or overpipetting by setting the median pore size in the porous plastic plug to the range from a specified value to an upper limit which varies with the hydrophobicity of the material of the plug. CONSTITUTION: A pipette device has a tubular tip 11 defining a sample reservoir, a porous plastic plug 12 mounted in the tubular tip 11 above the reservoir and suction means for applying suction to the upper end of the tubular tip 11 to draw air through the porous plastic plug 12 and to draw a liquid sample into the reservoir. The suction means have a control means for controlling the amount of the sample drawn into the reservoir to a precisely selected volume. At this time, the median pore size in the porous plastic plug 12 is controlled to the range from 3 microns to an upper limit which depends upon the hydrophobicity of the porous plastic plug so as to be small dimensions sufficient to prevent the suction device from drawing the sample through the porous plastic plug.