Two-piece sealing pipette tip

Abstract

A two-piece sealing pipette tip includes features to join the pieces in an air-tight manner without adhesive, and to seal the tip directly against the piston in an air displacement pipette, thereby avoiding the need for a piston seal within the pipette. This configuration reduces potential points of failure, allows the pipette-tip interface to be optimized, and improves liquid handling characteristics of the pipette.

What is claimed is: 
     
         1 . A pipette tip for use with an air displacement pipette, the pipette including a hollow shaft of generally tubular configuration and a linearly displaceable piston concentrically mounted for reciprocating movement within the shaft, the tip comprising:
 a hollow mount segment of generally tubular configuration, the hollow mount segment including a proximal end adapted for connection to the pipette and a distal end adapted for connection to a liquid handling segment;   a separate and hollow liquid handling segment having a proximal end and a tapered open distal end, the proximal end being of generally tubular configuration and adapted and dimensioned for connection to the distal end of the mount segment; and   an annular pipette-engaging mount projection extending outward from an outside surface of the mount segment near the proximal end thereof;   wherein the distal end of the mount segment and the proximal end of the liquid handling segment are dimensioned so as to produce an interference fit therebetween.   
     
     
         2 . The pipette tip of  claim 1 , wherein the interference fit between the distal end of the mount segment and the proximal end of the liquid handling segment also produces an air-tight seal. 
     
     
         3 . The pipette tip of  claim 1 , further comprising a membrane filter located between the distal end of the mount segment and the proximal end of the liquid handling segment. 
     
     
         4 . The pipette tip of  claim 3 , wherein the membrane filter is comprised of a generally hydrophobic polymeric material. 
     
     
         5 . The pipette tip of  claim 3 , wherein the cross-sectional dimension of the membrane filter is slightly larger than the cross-sectional dimension of the distal end of the mount segment, such that the membrane filter will bend around the distal end of the mount segment when the same is inserted into the proximal end of the liquid handling segment. 
     
     
         6 . The pipette tip of  claim 1 , wherein the annular mount projection is an integral part of the mount segment. 
     
     
         7 . The pipette tip of  claim 1 , wherein the annular mount projection is of substantially semicircular cross-section. 
     
     
         8 . The pipette tip of  claim 1 , wherein the mount segment and the liquid handling segment are comprised of the same material. 
     
     
         9 . The pipette tip of  claim 1 , wherein the mount segment and the liquid handling segment are comprised of dissimilar materials. 
     
     
         10 . The pipette tip of  claim 1 , wherein the mount segment is comprised of a material selected from the group consisting of polypropylene, another polymeric material impregnated with a lubricity-enhancing agent, and a thermoplastic elastomer having a hardness less than that of polypropylene or polyethylene. 
     
     
         11 . The pipette tip of  claim 1 , wherein the liquid handling segment is comprised of a material that includes a low-retention additive or coating. 
     
     
         12 . The pipette tip of  claim 1 , further comprising an annular piston sealing ring extending outward from an inside surface of the mount segment. 
     
     
         13 . The pipette tip of  claim 12 , wherein the annular piston sealing ring and the annular mount projection are located substantially equidistantly from the proximal end of the mount segment. 
     
     
         14 . A pipette tip for use with an air displacement pipette, the pipette including a hollow shaft of generally tubular configuration and a linearly displaceable piston concentrically mounted for reciprocating movement within the shaft, the tip comprising:
 a hollow mount segment of generally tubular configuration, the hollow mount segment including a proximal pipette connection end and a distal liquid handling segment connection end;   a separate and hollow liquid handling segment having a proximal mount segment connection end and a tapered open distal end, the proximal mount segment connection end being of generally tubular configuration and dimensioned and adapted to produce an interference fit and an air-tight seal with the distal liquid handling segment connection end of the mount segment; and   an annular mount projection extending outward from an outside surface of mount segment near the pipette connection end thereof, for retentive engagement of the mount segment with the pipette shaft.   
     
     
         15 . The pipette tip of  claim 14 , further comprising a generally hydrophobic polymeric material membrane filter located between the liquid handling segment connection end of the mount segment and the mount segment connection end of the liquid handling segment. 
     
     
         16 . The pipette tip of  claim 14 , wherein the annular mount projection is an integral part of the mount segment. 
     
     
         17 . The pipette tip of  claim 14 , wherein the mount segment and the liquid handling segment are comprised of dissimilar materials. 
     
     
         18 . The pipette tip of  claim 14 , further comprising an annular piston sealing ring extending outward from an inside surface of the mount segment. 
     
     
         19 . The pipette tip of  claim 18 , wherein the annular piston sealing ring and the annular mount projection are located substantially equidistantly from the pipette connection end of the mount segment. 
     
     
         20 . A pipette tip for use with an air displacement pipette, the pipette including a hollow shaft of generally tubular configuration and a linearly displaceable piston concentrically mounted for reciprocating movement within the shaft, the tip comprising:
 a hollow liquid handling segment having a proximal end and a tapered open distal end, the proximal end being of generally tubular configuration;   a separate and hollow mount segment of generally tubular configuration, the hollow mount segment including a proximal end adapted for connection to the pipette, and a distal end inserted into the proximal end of the liquid handling segment and retained therein through an air-tight interference fit; and   an annular pipette-engaging mount projection extending outward from an outside surface of the mount segment near the proximal end thereof.   
     
     
         21 . The pipette tip of  claim 20 , further comprising a generally hydrophobic polymeric material membrane filter located between the distal end of the mount segment and the proximal end of the liquid handling segment. 
     
     
         22 . The pipette tip of  claim 20 , wherein the annular mount projection is an integral part of the mount segment. 
     
     
         23 . The pipette tip of  claim 20 , wherein the mount segment and the liquid handling segment are comprised of dissimilar materials. 
     
     
         24 . The pipette tip of  claim 20 , further comprising an annular piston sealing ring extending outward from an inside surface of the mount segment. 
     
     
         25 . The pipette tip of  claim 24 , wherein the annular piston sealing ring and the annular mount projection are located substantially equidistantly from the distal end of the mount segment.