Repair and Calibration of Pipettes - PAGE 1
		    by Takashi Yogi

Scope: Pipettes made by Gilson or Rainin Instruments (Pipetman)

1. Care of Pipettes

	Don't let liquids get into the shaft of the pipette. This
happens when the plunger is released rapidly or when a filled
pipette is laid down. If liquid gets into the shaft,
disassemble, clean, and dry the pipette immediately. Otherwise
the piston will corrode and be ruined.
	Don't drop a pipette. The plunger rod is easily bent. Avoid
bending the shaft inside the P-10 and P-20; these units are very
delicate. Never let the plunger snap back on a pipette; this
changes the calibration.
	These pipettes should not be greased or oiled.
	Don't turn the dial far past the maximum volume; the knob
may come loose and ruin the calibration.
	Push straight down on the plunger button. Pushing sideways
produces errors and excessive wear.

2. Cleaning and Inspection

	Pipettes should be cleaned and the calibration checked
periodically.
	a. Remove the metal tip ejector by grabbing it firmly and
pulling it away. Unscrew the plastic coupling nut to separate
the shaft from the body. Remove the piston assembly while noting
the order of the parts.
	b. There should be a white teflon seal and a black o-ring
either on the piston rod or inside the barrel. Inspect these
parts and replace both if the teflon seal slides loosely on the
piston rod.
	c. Clean the piston rod with a kimwipe and water. Don't use
any abrasive cleaners. Inspect the rod carefully for any residue
or corrosion. This is a polished piece and must be absolutely
clean and shiny. Even the slightest flaw will make the pipette
unreliable. For example, a damaged piston may deliver 50
microliters correctly, but fail at 70.
	d. Re-assemble the pipette, noting that the o-ring
surrounds the teflon seal and that the narrow part of the teflon
seal points toward the tip.
	e. Rotate the plunger knob to check that the plunger rod is
straight.
	f. Replace the tip ejector by pushing it firmly back in
place. There should be a slight gap between the ejector and a
pipette tip. If not, the ejector is not fully in place.

3. Calibration

	a. You will need an electronic analytical balance, a
weighing dish, a microfuge tube, a beaker of DI water, a 2 mm hex
wrench, and a calibration tool. Calibration tools may be borrowed
from room 229.
	b. You will pipette the water into either the microfuge
tube for P10 to P200 pipettes or into the weighing dish for P1000
pipettes. The microfuge tube is used to reduce the error due to
evaporation.