Dears,
Can anyone guide me in how to read and FTIR scan of lub oils effectively?what does all those peaks indicate?
or
suggest some reading materials..
thanks
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There is at least as much art as science to reading an FTIR. A used oil scan is pretty much useless unless it's compared to a reference scan of the unused oil. That way you can watch additives deplete, oxidation increase and gremlins creep in, if you know what you're looking for.
You can look at these paired scans in an overlay to see "before & after" or you can have the machine subtract one from the other to get a fairly flat line that accentuates the differences between the two.
These are not like GCs, where for a given method, a given compound appears as a single peak at a specific retention time. FTIR is not a separation method like GC. Each type of bond in a molecule will absorb IR light at a specific frequency, sometimes more than one. Since most molecules have several different types of bonds, a given compound will show multiple absorbances. So, each peak is not one molecule, it's part of a molecule. If several molecules in a formulation have the same type of bond, each peak may be part of several molecules, with each one of them having various other absorbances that create the "signature" for a given molecule. When you have a mixture of chemicals (as in lube oil) it can be very difficult to figure out exactly which absorbances belong to what. That's why most FTIR library searches give you a list of possible chemicals in order of probability. Like I said, as much art as science.
The lab that ran the scan for you should be providing you an interpretation as well. They certainly are not intuitively obvious results like a viscosity or a pour point.
Beware, if the lab that ran the scan does not have access to the details of the formulation, that will limit what they can tell you. I've seen cases where these labs over-interpret.
Does that help?
You can look at these paired scans in an overlay to see "before & after" or you can have the machine subtract one from the other to get a fairly flat line that accentuates the differences between the two.
These are not like GCs, where for a given method, a given compound appears as a single peak at a specific retention time. FTIR is not a separation method like GC. Each type of bond in a molecule will absorb IR light at a specific frequency, sometimes more than one. Since most molecules have several different types of bonds, a given compound will show multiple absorbances. So, each peak is not one molecule, it's part of a molecule. If several molecules in a formulation have the same type of bond, each peak may be part of several molecules, with each one of them having various other absorbances that create the "signature" for a given molecule. When you have a mixture of chemicals (as in lube oil) it can be very difficult to figure out exactly which absorbances belong to what. That's why most FTIR library searches give you a list of possible chemicals in order of probability. Like I said, as much art as science.
The lab that ran the scan for you should be providing you an interpretation as well. They certainly are not intuitively obvious results like a viscosity or a pour point.
Beware, if the lab that ran the scan does not have access to the details of the formulation, that will limit what they can tell you. I've seen cases where these labs over-interpret.
Does that help?
You can try searching the noria website - I've come across some good articles on FTIR. Also read ASTM E2412 - these will give you the wavenumbers and the peaks. Google some articles written by DR Dave Wooton - the man is a guru on FTIR. You can also check out www.wearcheck.co.za - look in publications - technical bulletins. There is a really good article on FTIR and oil condition monitoring.
The FTIR test method does not necessarily compare a used oil spectrum to a new oil spectrum - this is only the spectral difference test method, most labs I know are using JOAP method - I'd suggest you visit your used oil analysis lab to check it out and see which method they use. Ask one of the chemist there to explain how the FTIR works, what peaks they are measuring and have a look at a spectrum.
The FTIR test method does not necessarily compare a used oil spectrum to a new oil spectrum - this is only the spectral difference test method, most labs I know are using JOAP method - I'd suggest you visit your used oil analysis lab to check it out and see which method they use. Ask one of the chemist there to explain how the FTIR works, what peaks they are measuring and have a look at a spectrum.
Hardy,
Lamont is correct in that there is as much art as science in interpretating FTIR and a reference is necessary for an accurate interpretation. What information do you hope to get from the FTIR? Oil degradation,contamination or additive depletion?
Lamont is correct in that there is as much art as science in interpretating FTIR and a reference is necessary for an accurate interpretation. What information do you hope to get from the FTIR? Oil degradation,contamination or additive depletion?
hi all, so much for art in ftir interpretation. can anybody tell me how to explain it in scietific way but not too technical. how do we go about this, for example we have a chemical and we have a sample thought to be contaminated by the chemical.
Can anyone guide me that the FTIR can be determined quantitative for soot,oxidation, nitration,glycon and How?
