pipetting sticky solutions - (Dec/14/2007 )
No problem with the initial prelevement, because I weight it ! ( however you need to know the density), hehe !
Of course, we don't cut the tip if we are to pipet 1000ul with a p1000.. If we are to do so, we go for two shots of 500 ul. And positive displacement are not something we can afford
Anyway, the predilution is the best possible way. But you'll have the same problem with the initial prelevement of the solution, hehe!
In normal pipettes, the volume delivered is the tip volume plus the volume in the barrel. Logically, if you cut the tip, you reduce that component of the equation, therefore less liquid delivered.
you'd think so but...
the plunger movement (inside) is the true measure of the amount pipetted (volume is not dependant on width or lenght of tip) - the only thing you have to be carefull of is making the hole too big as stuff could drip out or air be sucked in.
sometimes i need to use Triton-X or Tween solution which deny to enter into pipette, so one way is to pipette very slowly
but i mostly manage it by measuring in weight.
I dont think in this case % conc needs to be very precise, therefore, whatever the easiest and cheapest way to achieve that is good. Cut the tip off, withdraw slowly your sample and rinse it with solution that you are going to dilute with.
These are all good solutions for very small (pipet-tip) volumes. I've struggled with dispensing methylcellulose into petri dishes with glass serological pipets, because of its viscosity and stickiness to the glass. Do we have any solutions on the scale of milliliters rather than microliters?
a 10 ml syringer?