FTIR Cary 630 - Simethicone Identification

Question

Hello everybody, 
 
 I have a problem in the identification of simethicone capsules. I am currently following the USP method, which indicates that I should use the standard solution, blank and sample solution according to the assay, therefore, the samples are diluted in toluene, circa 2,5 mg/mL. 
 I have created a new library and added the spectra of standard and blank. The problem is when I compare the spectra from the library with the spectra from a recently prepared standard I get good similarity results in both the comparision standard-standard and standard-blank. This way I can&acute;t properly identify simethicone in a quantitative way, because there is no significant difference between the responses. Also, the scalling is not helping me to do a qualitative comparision, because It is auto-scaled (0 to 1). Is there any way to fix the false positive result and to adjust the graffic scaling?

First one is standard, second one is blank.

Scharf · Accepted Answer

Hello David, 
 I have contacted the agilent services here in Brazil and It appears that I have made a mistake during the pathlength method. I used toluene as background, so the pathlength resul was not correct. Here are the correct results: 
 0.5mm cell: Value = 501,89 
 
 0.1mm cell: Value = 100,37 
 
 Do you have any more ideas on what is happening with the saturation? I think that the 0.5mm cell is too sensible for the identification analysis, but the USP Method states that the 0.5mm cell must be used.

FTIR Cary 630 - Simethicone Identification

Top Replies