Pipette tip and filter for accurate sampling and prevention of contamination

A pipette tip assembly, comprising:

• a hollow tube, said tube defining a first end, a second end opposing said first end, and an inner surface defining a volume, said tube defining openings at said first and second ends, said tube having a vertical orientation such that when said tube is oriented vertically said first end is uppermost;
• and
• a filter inserted between said first end and said second end of said tube such that said tube and said filter define a sample reservoir between said filter and said second end;
• said first end of said tube comprising attachment means for attachment of said tube to a suction device for drawing fluid into and expelling fluid from said sample reservoir through said second end of said tube;
• and
• said filter comprising a plurality of cylindrical micro fibers cohesively bundled as adjoining columns such that when said filter is not compressed, the cross-sectional horizontal density of said micro fibers per square millimeter closely matches a predetermined value, said micro fibers oriented vertically lengthwise as defined by said vertical orientation of said tube, each of said cylindrical micro fibers having a core of an autoclavable material and an outer coating of a hydrophobic material, said micro fibers compressed against each other and said inner surface of said tube such that said micro fibers and said inner surface of said tube interstitially define a number of vertically-oriented pores having a pore distribution and such that said micro fibers seal against said inner surface of said tube, said pore distribution defining varying pore sizes within said filter, said pore sizes dependent upon said volume of said pipette tip and said cross-sectional horizontal density, whereby said pore distribution of a first filter will be consistent with said pore distribution of a second filter where said first and said second filters are inserted into pipette tips having equal size and shape at the same position within said volume.