Welcome everybody.
Today we're going to be talking about micropipetting. You're going to learn
how to use a micropipette,
going to learn what it is, and we're going to go through a little demo of how to do that.
This is a micropipette.
This happens to be an eppendorf,
and of course there are different
volumes of micropipettes.
Here we have
a 10 microliter
micropipette
a 100 microliter micropipette
and there are different volumes. This happens to be of 1000 microliter
or 1 mil
micropipette.
Of course we want to be able to change the volumes. These are variable volume
pipettes and you can see
from this dial...
I'm dialing the volume down
and this way up.
So I'm going to set this at
one 1,000 micro liters
and we're all set to go in a couple of minutes because first you can see
here on the bench
that i have a test tube filled with red liquid. It's an aqueous solution -
water and some red pigments
and you can see
along the very front of this
tube
that the the water
makes a crescent shape.
This is called the meniscus,
and this is because of a few properties of water
one of which is adhesion.
So water adheres to the
container that it's contained in.
Cohesion - water molecules adhere to each other,
and surface tension -
water molecules adhere very closely to each other at the interface between
the air
and the top of the water.
So how do we use
one of these
micropipettes?
The first thing that I'm going to do of course
is set the micropipette tip
onto the micropipette.
I'm going to press down firmly
but gently,
and lift straight up.
And we'll get rid of that now.
Now you have to expel the air
from the the barrel of the micropipette
before putting it down into the liquid - into the center of the meniscus.
if we don't then
we're going to get a whole bunch of bubbling
which will really interfere with our ability to make precise measurements.
So we're going to expel the air
first. Push down to the first stop
go down just below the meniscus into the center.
We're going to pre-wet
the tip slowly
a few times,
up and down,
so that our measurement is going to be accurate...
nice and easy.
And then we're going to pick up
our 1.5 mil tube and
at eye level
we're going to slowly expel to the first stop
and then
to the second stop.
Then we release
the barrel after we've taken the micropipette tip
out of the solution.
So that's basically
how you perform
micropipetting.
it's not difficult but it does require
technique and it does
take practice.