A. Poe: Hello everyone. My name is Abigail Poe and I’m a Research Associate here at NCPTT.
I’m welcoming you in our lab today to talk about this instrument here, which is the FTIR
or Fourier-Transform Infrared Spectroscopy. So, this instrument can be used to help us
identify compounds by looking for functional groups that are contained in them. So, if we
break it down, the FT part, Fourier-Transform stands for a mathematical technique that takes
the raw data and converts it along with the help of a computer, into meaningful spectrums.
On the other hand, the IR part stands for infrared spectroscopy which is the type of
light that this instrument uses, and it also is the molecular vibrations that the light
produces as it interacts with the compounds. So, we can use this instrument for a lot of
different techniques in our lab. So, we can look for identifying unknown
compounds or materials, as well as surface contaminants or we can look for how deeply these
chemical penetrate into the substrate itself. So, for like my project specifically, I’m studying
how herbicides affects the properties of historic stone and masonry materials. So, one of the tests
that I’m using with this is in addition to looking at whether there’s herbicide residues left on the
surface, I’m interested in seeing whether any of them have penetrated into the material itself.
So, I’m performing a test with this to see if the artificial accelerated weathering process,
pushed the herbicide into it and how deeply that penetration occurred. So, as you can see,
we can use this instrument for a host of tests that tell us a bunch of useful information.
So now, I’m going to start talking about the two different components, the first being ATR,
which is this one right here. ATR stands for attenuated total reflectant. So, this test can
be used for solids and liquids. If we use it with solids, it’s typically a destructive test because
it requires us to powderize the samples, like you can see I’ve done here. So, the liquid or solid is
placed onto a crystal, which we have here, a beam of infrared light is passed upwards, interacts
with this material and this interaction produces a spectrum of the absorption of that light.
So, that spectrum reveals useful things. Again, like the functional groups and other
information that we can use in identifying the compound. So, this test is relatively
simple to perform because it doesn’t require a whole lot of sample prep and it’s fairly
consistent in the results that it gives us. On the other side we have an IR microscope.
The IR microscope is useful for mainly solids is what we use it for in our lab,
like this piece of granite that I have here. It can be used for non-destructive tests and letting
us just take the sample as a whole and looking at things on the surface, or we can also cut a
sliver off and test for things like the depth of penetration that I was talking about earlier.
So, the microscope actually uses liquid nitrogen which I’ll be demonstrating in
a little bit to help keep it cool and prevent it from overheating as we’re running these tests.
So, I’m going to be showing you how to use the ATR with this limestone sample that I have here.
Like I mentioned, when we have a solid like that, we typically powderize it.
So, I’ve got some powder that I collected earlier in here and it doesn’t really take much.
Close this handle right here so basically, we’re now ready to take the IR specs,
so that ensures that we now have contact of the powder with the crystal itself. And I
press that button that there so we can run and get the spectrum which you’ll be seeing later.
So, now I’m going to be using the microscope and
the first step that I’m going to be doing is adding the liquid nitrogen.
So, now we’re going to be looking at one of my granite samples under the microscope, so
this test is specifically looking for whether the herbicide is on the surface of this sample itself.
I’m just focusing the light source right now and making sure it looks clear in the microscope
before I collect my sample. So, now that I’ve got it sufficiently clear, I’m going to go ahead
and run the microscope which will collect the spectrum, that we’ll see on the computer later.
So, now that we have our spectrum, we come over to the computer where we’re going to analyze them,
and you can see here a couple of representative spectrum that are produced from some of my
earlier samples. But I’m specifically going to be focusing on the limestone one itself,
so I’m going to switch over to that really quickly.
So basically, we have a program on our computer that’s filled with reference libraries. So,
what that does is it compares our spectrum to spectrums that we have from other software or
spectrums that we’ve added from known substances, known chemicals, and it looks
for matches in our spectrum to those. So, I’m going to run this one through
this to see if we get any matches and again this is our limestone sample.
And it doesn’t really take long to do this. As you can see, it’s already done. It’s going to
pop up matches and so if we look on the list, our actual first match is calcium carbonate,
which we know is in limestone, so it has identified one of the components in limestone. So,
you can see this is very helpful in helping us identify what groups are in
the materials and the chemicals and the substrates that we’re using, so that we’re able to identify
whether, again like I said, there’s contaminants or maybe for like my project, herbicide residues
left behind. Or if we have an unknown material, we can also try to identify it this way.
So, that’s pretty much it. You can see this is a pretty useful instrument in the lab
and I guess I’m going to get back to analyzing the rest of my samples,
but it’s been a pleasure to show you a little bit about this instrument,
and if you want to find out more about this one or the other ones, you can visit our website and
our you tube channel where we have several videos. Thanks for watching and if you have any questions,
put them in the comments below and we’ll be glad to answer them. Thank you.