Practical tips for pipetting small volumes

There’s lots to say about pipetting little amounts!

Firstly, if you don’t have to, don’t! Avoid it altogether!
pre-dilute concentrated solutions so you can pipet larger volumes
use mastermixes when possible: http://bit.ly/mastermixesmultichannels ;    • Mastering master mixes - calculations...  
“never” try to pipet less than 0.5 μL

Don't pipet into thin air!
pipet into liquid or onto wall of container so surface tension can help pull it all out

Check to make sure the liquid's really there!
look at the tip to make sure the liquid got sucked up (without bubbles) and all got dispensed out
if there is still liquid in the tip, go back in, pull up until liquid reaches the trapped liquid and use it to drag that liquid back down
make sure the liquid line is consistent each time

Alter angles to achieve accuracy
aspirate (suck up) vertically (and slowly)
avoids capillary action causing you to suck up too much
dispense (slowly) at a 45° angle
helps it all gets out

Make sure to practice proper thumbmanship
only go to first stop when aspirating (don’t push thumb all the way down at this point)
go to second stop (all the way down) when dispensing
pause (with thumb pushed down) before pulling out
keep thumb pushed down when you pull out
pull out slowly, making sure all the liquid gets pulled out before you release your thumb
if there is still liquid in the tip, go back in, pull up until liquid reaches the trapped liquid and use it to drag that liquid back down

Stay just below the surface
avoid liquid sticking to outside of tip (look to make sure as well)

Use the smallest possible pipet
use P2 when possible, especially for volumes under 1 uL

Use low-binding tips

Call that calibrator!
make sure the pipets are regularly calibrated to ensure accuracy

To err is human, and/or humidity
differences in air temperature inside the pipet tip can alter the pipetted volume; if the air is warmer inside, liquid will evaporate and decrease the actual liquid volume
avoid warming up the air in the pipet
don’t hold on to the pipet while you’re waiting around
pre-wet the tip?
pipet up & down several times first
eppendorf recommends this, but anecdotally I’ve had trouble with this due to sample getting stuck on in tip and altering volumes, etc.
Practice
pipet drops of water onto Parafilm on an analytical scale
water has a density of 1 g/mL, so 1 mg/μL, so if you pipet 1 μL, it should weight 1 mg. each time

blog version: https://bit.ly/pipettingsmall

resources:

Eppendorf, “How to Pipette Small Volumes with Handheld Manual Pipettes”, 09/19/18 https://handling-solutions.eppendorf....

Gilson, “Pipetting Small Volumes: 4 Tips for Improving Your Technique” https://www.gilson.com/default/learni...

ThermoFisher Scientific, “Proper Pipetting Techniques” https://www.thermofisher.com/us/en/ho...

more pipetting tips:    • Pipetting tips      
    
more practical lab tips & tricks: https://bit.ly/lab_tricks_page &    • Practical lab tips & tricks  

more on accuracy vs. precision: https://bit.ly/accuracyprecisionerror ; YouTube:    • Precision vs accuracy  
       
more about all sorts of things: #365DaysOfScience All (with topics listed) 👉 http://bit.ly/2OllAB0 or search blog: http://thebumblingbiochemist.com