Does anyone have tables to convert %soot to %transmittance for IR spectrometry? And if possible to % CAT allowable.

didicoi_2004@mail.ru

Marat,

Most labs would have correlated the absorbance reading obtained from the FTIR to a %soot value. The % soot value is obtained from using TGA analysis. You need to speak to your FTIR supplier to setup an algorithm for correlating the soot absorbance to %soot values. It is generally done on hundreds of samples using a line of best fit to come up with the correlation. As for the CAT % allowable, it is propriety information so most labs will not divulge that information or do not know it. In some cases, it is already setup as part of the software package with the labs.

Please don't take this as the definitive answer - but I have literature indicating that on your typical FTIR you divide the FTIR result for soot by 51 to get the soot %. This works on the DIGILAB FTIR and I think its the same for the Varian machines.

I hope this is the kind of thing you were wanting, please indicate if you would like me to send you the document - indicating the tests done to correlate the 2 values.

That is a good trick that we used for a long time on our Bio Rad (pre Digilab) then we found a source of TGA commercially available soot standards. It was very liner throughout all the ranges of the standards that we purchased.

When the stadards expired, we tried to buy more, but that source went out of business, or dropped off the map for some reason, (not enough of you folks out there bought their product and supported them!!)

Just joking, but we did see at the recent Lube Excellence 2007 that VHG is considering offering a commercially available soot standard. Maybe if enough folks support them in this regard, we can all keep it as a vaiable source of standard so we can all agree on soot by FTIR.