CHAPTER 11: USE OF OXFORD® DIGITAL DIAL PIPETS
Carefully following these steps will repay you with better results in your work.
1. Set the volume by turning the adjusting knob that is the top of the plunger. Do not turn
the knob to beyond the maximum or minimum ranges listed on the top of the pipet.
2. Put a disposable plastic tip on the end of the pipet by inserting the bottom of the pipet
into a tip in a rack. Do not use your hands to remove a tip and then put it on the pipet.
3. Secure the tip better by grabbing the top of the tip and pushing it on tighter while
twisting. Do not touch the tip more than 2 cm from the top - if you do, you could
introduce contamination into your solutions.
4. Push the plunger of the pipet down to the first stop position before putting the tip into
the desired solution. If you were to insert the tip into the solution before doing this,
you would blow bubbles out of the tip, and a small bubble of air would remain at the
tip, preventing you from pipeting accurately.
5. Insert the bottom of the plastic tip just below (approx. 1 mm below) the surface of the
solution you wish to withdraw, while holding the plunger at the first stop. The best
way for a right-handed person to pipet is to hold the tube or bottle containing the
solution with the left hand at eye level 4 to 6 inches from the face, so that the fluid can
be seen clearly. Hold the pipet with the right hand. This procedure can even be used if
you are making solutions on ice. Simply pick the tube up from the ice by holding it at
the top (so that you are not heating the solution at the bottom much) and keep it off the
ice as briefly as possible.
6. While holding the tip just below the surface of the solution, release the plunger slowly.
Don't just let the plunger snap up. (If you were to allow the plunger to snap up the
pipet will not draw the proper volume of fluid. This is critical for accurate pipeting of
all solutions.)
7. Remove the tip from the solution.
8. While holding the tube that will receive the solution at eye level, put the tip of the
pipetman into the recipient tube.
9. If the tube is empty, place the bottom of the tip along the side of the tube near the
bottom. If the tube has some other solution in it already and you want to mix the
solution being delivered, put the bottom of the tip just below the surface of the
resident solution.
10. To eject the solution, press the plunger down. You will notice that when you reach the
first stop on the plunger there will still be a small amount of solution in the tip. To
expel this last amount, depress the plunger fully.
11. To prevent solution from re-entering the tip, you must remove the tip from the solution
or away from the side of the tube while still fully depressing the plunger. If you do not
do this, you will make the very common mistake of sucking solution up into your tip
even well past the set volume.
12. Discard the tip by pressing the tip ejection button. Tips should be placed into the
regular trash baskets. You may wish to collect used tips at your bench instead of
running to the trash with each tip, but be sure to use a fresh tip for every operation.
Practice Settings
We have three sizes of digital dial pipets, each with color-coded dials on top: 0.5-10 µl (white), 10100µl (yellow), and 100-1000µl (blue). They are referred to, respectively, as: P-10, P-100, and P1000. The color-coded dials indicate the size and color of protective plastic tips to be used with each.
Volumes are dialed in using the colored knobs while reading the four digit setting in the window. If a
window has a horizontal line through it, indicated in the window boxes below by a bolded line, you
are to read a decimal at that line.
NOTE: Pipets should never be dialed above or below the volumes indicated on the pipet.
P-1000: to set 950 µl
(has no decimal indicating line)
0
1000's of µl
9
100's of µl
5
10's of µl
0
1’s of µl
P-100: to set 75 µl
0
100's of µl
7
10's of µl
5
1's of µl
0
0.1’s of µl
P-10: to set 10.5 µl
1
10's of µl
0
1's of µl
5
0.1's of µl
0
0.01's of µl
Dial and Plunger
Button
Volume Setting Lock
Tip Ejector Button
0
Volume Setting
Window
1
2
5
Filter
Figure 1. Representation of an Oxford® digital dial pipet.