For the quantification of hexadecanoic and octadecanoic acids

Question

We have recently been working on the quantification of hexadecanoic acid and octadecanoic acid. 
 We used a Cary 630 FTIR and Dialpath 200 &mu;m photometry.The quantitative peak is 2855nm 
 The first graph shows the superimposed spectra of 25mg , 4mg , and solvent

The second graph shows the 4mg, 0.4mg, and solvent stacking spectra

Is there anything I can do to enhance the response of 0.4mg hexadecanoic and octadecanoic acids?

Vincenzo · Answer

Hi Duxact_J 
 
 I've couple of comment on it. 
 The first one is about the background, as i see you are getting a negative Abs, you may consider to check what is causing this shift, this is not affecting the results and the shape but maybe the overrange is scaling the whole spectrum. 
 The second point, about you question is, as you surely know the power of the DialPath is to adjust the Path at needs, so to enhance the signal at 0.4 my suggestion is to use a longer path (keep in mind the Lambert-Beer Equation) and create multiple calibration curves for quantification to be more accurate. 
 As example 3 curves with concentrations between 
 0.3 to 2 mg with the longest Path 
 2 to 10 mg with 200 um 
 10 to 25 mg with 200 um 
 
 and then load all the three model on the same Microlab Method and choose the proper results on the correspondent calibration curve. 
 
 Another try might be to use a Ration between the quantitative peak (2855wn) and a isosbestic point (If you have one) at the lowest Abs.