I have been a bit remiss on the blog ( for a moth or two!!) – sorry but I am back into it and here goes.
Often we get bits of material brought into the lab and are asked to check them out and see if they are what they should be. The simple way of doing this sort of work is to stick it onto the FTIR spectrometer. This is a great instrument. In 45 seconds you can get a spectra which is a chemical finger print of the material. Then you can search against the database of 15,000 spectra and get a match. So all of this can be done in less than 5 minutes with no need to do anything with the sample as it just gets clamped against a small diamond crystal in a stage. This is an amazing technique and generally works very well but when you have a complex sample you can end up with a very complex spectra which can be difficult to pull apart. (We have a software package that tries to do this but to be honest it struggles unless it is a simple 2 component mix without too many overlapping peaks.)
We have another instrument which in its own way is as powerful but it works on different principle-it is the GC-MS (gas chromatograph- mass spectrometer).
This first stage separates out the various components int he sample (that’s the GC bit) and then gives them an electric charge and fires them along a vacuum chamber and by applying an electric filed it can measure the mass of the ions that are produced (the MS bit). From looking at the masses of the ions you can work out the structure of the unknown material. (we have a database of 2,000,000 mass spectra to check against)
So the FTIR gives you chemical information about your sample and the GC-MS gives you mass information. Using them together works well because they complement each other. Unfortunately the GC-MS can only handle liquids that can be vaporized.If you want to look at solids on the GC-MS you have to carryout extractions with solvents which is laborious and will only pull out certain materials.
We have just got our hands on a sampling accessory that allows us to handle solids and run them through the GC-MS. It is a pyrolysis injector.
This will take a solid sample and heat it up- the gases given off are then sent into the GC-MS which then analyses them. Methods can be built that will do this in a multishot sequence eg an intial run up to 150°, that will release any solvent, then a second run up to 300° that will release any unreacted components, followed by a final run at 700° that will burn off the polymer. The beauty of it all is that there is no sample preparation required and the multishot pyrolysis is done sequentially on the same sample, which makes it a fast and simple. This all comes with its own data base of common pyrolysis products which can be used for searching any unknown peaks so the analysis is simple as well.
We are really excited and can’t wait to get it all working. Hopefully it will add another “string to our bow” when it comes to us investigating our customers materials issues.