We're going to go through a capillary electrophoresis experiment, which is a separation
technique. We're going to look at five different drug compounds that are commonly found in
over-the-counter medicines. First we're going to make a set of standards: one of each of the
different drugs that we're going to look at. Then we'll make a mixture of those compounds, run those
birth through the instrument, and then we'll look at a real sample and see how that compares.
The first thing we need to do is weigh out 20 milligrams of each of our different analytes.
First we need to add the...
...I've totally forgotten the word.
What are they called?
[Sample vial, isn't it?]
Yeah that's it, thank you.
Alright, so first with the sample vial onto the balance, and we tare the balance, to get that to
zero. We remove the sample vial from the balance. We want to weigh out 20 milligrams, or 0.02 grams.
We return that to the balance. That's now measuring 21
milligrams. We'll take that from the balance, and add that to our volumetric flask.
You need to fill the volumetric flask to the meniscus. To start with, you can just add water
into the flask. Once you're close to the meniscus, use a glass pipette to fill up accurately.
Once the flask is full, we're going to mix a few times to ensure that all the compound
is fully dissolved in the water.
So now we've made all our different solutions we need to start by putting the different
standards through the instrument to obtain the retention time of each individual component.
So the first thing we need to do is load our samples and buffers into the instrument.
Once we've added all six vials, we close the lid of the instrument
and we just need to set up the run.
To start the run just press start.
As we can see we've got our five different components, and they all come off as nice
well-resolved peaks. Giving us five components of our sample, and five nice sharp peaks on our plot.
The final stage of this experiment is that we'll prepare a paracetamol tablet for analysis. The
first step is to take your whole tablet, place it into a pestle and mortar, and then you're going
to grind it into a fine powder. Once you've got your fine powder, you want to transfer that into
a large one litre volumetric flask, then we're going to fill this again up to the meniscus.
Some of the bulk agent probably won't dissolve, and that can be seen as just
small bits of white powder floating around in the solution. So what we'll do before
we analyse this, we'll pass it through a 0.54 micrometre filter
to remove any of the solid particulate matter that would interfere with the instrument.
We analysed our sample with our paracetamol,
and that's our large peak that we can see here that was eluted at 2.5 minutes.
This is a really useful technique for separating
different compounds that may have quite similar molecular structures but that have
different charges and then different charge to mass ratios. We get nice separation which
we can use to either identify them or even to quantify the amount of a product in our samples.