Page 149 - Illustrated Pocket Dictionary of Chromatography
P. 149

PISTON    149



               Si   O    OCH 2 CH 3
          Surface  O               H      R     O

               Si  O               N      *  N                NO 2

                                      O      H

                       Pirkle "type" bonded phase
                                                       NO 2


        piston  A finely machined component of an HPLC pump that
        moves into and out from the piston head. Its movement forces
        mobile phase flow through the system. Many pistons used in analyti-
        cal LCs are constructed from sapphire. For semipreparative and
        preparative units stainless steel and ceramic pistons are more
        common.



























        Three different piston-piston seal combinations are shown above. The left and right
        sets are for an analytical HPLC system; the middle is from a column-packing pump.
        Note that the larger diameter of the center pump will allow for faster flow rates
        (displaces more volume per piston stroke).
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