you can refer to chapter 3 from this book (Stuart, B. "Infrared Spectroscopy: Fundamentals and Applications. 2004." JohnWiley & Sons, Ltd.). It contains a simple introduction on how to use FTIR for quantitative analysis. 

Here is the article which explains use of IR spectroscopy for protein quantification:

http://www.genengnews.com/gen-articles/ir-based-protein-peptide-quantitation/4586/

ATR-FTIR can be effectively used for quantitative analysis. Non-destructive measurement of samples is possible using ATR-FTIR. Prepare known concentrations of your samples and analyze. For this you must know the prominent IR peak in your sample. Measure  peak heights/areas and prepare a calibration curve. From this you can determine the concentration in unknown sample by noting peak height. 

Now a days all programmable software's are coming in built into ATR-FTIR (iCIR) by which we can directly build quantification models (PLS/PCA) based on peak height/area for quantitative analysis. It is useful for in situ and continuous analysis.

I quote the answers. You need to make the standards at various concentrations , and make a calibration curve , as spectroscopy or HPLC.

It depends on what kind of material you are analyzing. If your material varies in composition as a function of time or temperature, the thickness of your sample may vary too (e.g. due to evaporation of solvent etc). In such case, you have to select a peak that remains constant (not shifting) during the entire process. In absorption mode, find out the area (not the height) of the main peak (of your interest) and divide with the area of the constant peak. A simple macro or inbuilt profile creator will help you.

I endorse the answers of Dear Rahul & Atul. Further following thread and attached file may be helpful in this regard.

http://www.nobel.gen.tr/Makaleler/IJNES-Issue%202-5a9facb839c94130ace1e21446e44e37.pdf

http://turroserver.chem.columbia.edu/PDF_db/theory_ftir.pdf

Exactly as UV-Vis. You should measure the absorbance of your sample and interpolate in the calibration curve. Take care with your baseline.

Further more, you can use PLS regression for quantification and PCA for sample classification or trend observation.

Rahul Kalhapure Sir, can you please share more information about calculation part or any related papers.

Jagdish Paithankar please follow below link-

https://www.agilent.com/cs/library/applications/si-1374.pdf

Has any of you tested quantitative or semi-quantitative analysis on FTIR-DRIFTS datas?

Nice one Rahul

It depends on several factors, but I have used it quantitatively for siloxanes in the past. What are the groups you are measuring? Do you have a selective wavelength or frequency? What LOQ do you require?

Remember, weak radiation gives you a weak response!

Thank your Bruce beagle for your answer. I’m looking for PDMS in vagina when condom have been used in rape cases. I’m working with drifts analysis. LoQ should be as low as possible ;)

My LOQ was about 25 ppm. The frequency was 1620 cm-1 (well separated).

Nice ! 25 ppm is enough for me ;)

I will try with 1620 cm-1 ! Thank you !!!!!

The attached 2 papers may help you.

Good Luck

Thanks a lot :)

You can use the intensity of the absorption peak to quantify the measurements. Generally, we use the relative increment of elevation of absorption peak to measure quantitatively the raise of density of functional group.

Best wishes

Dear Dr Yogehs. It seems that you have sent the same paper twice, am I correct? Could you please suggest another sources? With best regards, Felipe

Just remember weak radiation (with FTIR), weak response. If you require

Nice

Long thread, but some important things have not been mentioned. First of all, if you do a calibration of your absorbance data against concentration, do not force a straight line through it! Why? First of all, absorbance is generally non-linearly depending on concentration, even in the absence of chemical interactions:

Article Beer's Law – Why Absorbance Depends (Almost) Linearly on Concentration

Article Deviations from Beer's law on the microscale - Nonadditivity...

Try to use integrated absorbance instead of absorbance peak values:

Article Beer’s law – why integrated absorbance depends linearly on c...

Avoid situations, where you have multiple reflections inside the sample (e.g. films). In these cases the wave nature of light has to be taken into account and that absorption (not absorbance!) is proportional not only to the absorption constant, but also to the electric field intensity (E2):

Article The electric field standing wave effect in infrared transfle...

Article The Electric Field Standing Wave Effect in Infrared Transmis...

If you cannot avoid them, treat them properly:

Article Removing interference-based effects from the infrared transf...

Understand that ATR has some problems of its own:

https://www.researchgate.net/post/ATR_correction-why_would_you_not_use_it

Understand why you need to measure a blank matrix pellet, e.g. for the KBr technique:

Article Employing Theories Far beyond Their Limits-The Case of the (...

If you do Band fitting, why would you prefer a Lorentzian (and why not...)

Article Quantitative Evaluation of Infrared Absorbance Spectra - Lor...

And, last but not least, what is behind the concentration dependence of absorbance:

Article Beer's law derived from electromagnetic theory

Some questions are still open... the problem is that the Bouguer-Beer-Lambert law is not in general compatible with wave optics and dispersion theory... we are working on this...

I think these articles may be helpful:

Article FTIR combined with chemometric tools (Fingerprinting spectro...

Article ATR-FTIR coupled with Chemometrics for quantification of vil...

Article Attenuated Total Reflectance Fourier Transformation Infrared...

Article Chemical fingerprinting and quantitative monitoring of the d...

Article Surface enhanced infrared absorption spectroscopy (SEIRA) as...

Yes, FTIR can be used for quantitative analysis. For instance via multivariate analysis, you first train a model by using appropriate multivariate analysis method (such as Partial least square regression (PLS-R)) on spectra of samples of known concentration (after appropriate pre-processing), then use this model to predict the concentration of samples of unknown concentration. Programs such as Unscrambler and essential FTIR, and the Hyperspec package in R, etc. can help you in performing such studies.

Is someone has experience with the direct detect from Merck to quantify proteins?

Agree with Omar Elkadi. You need to go for multivariate analysis using variable concentration of standard with sample, identification of principal component, PLS analysis, preparation of model, testing of prepared model via prediction of known concentration sample. If difference between Regression coefficient of prediction and model is very close, then use for analysis of unknown concentration samples

We have recently reviewed the optical limitations of the Beer-Lambert law for all who are interested in quantitative analysis with infrared spectroscopy:Article The Bouguer-Beer-Lambert Law: Shining Light on the Obscure

Here you find lecture notes detailing how to perform a sophisticated quantitative analysis of IR spectra far beyond the Beer-Lambert approximation: Preprint Wave optics in Infrared Spectroscopy

Yes FTIR can be used for quantitative analysis of medicines by comparison of sample peaks with standards e. g. aspirin. % age composition of a product can be determined by comparison of peaks by the help computer software automatically.

The analytical method gives the purity of sample and its functional groups and resemblance to the standard peak. The peak development with the absorbance also signifies the transmittance and concentration confined to the area under the peak

Not sure you would have a constant peak for peak ratio when you are doing mixtures of one substance into another to generate a calibration curve. Any peak would vary with changing concentration of the peak of interest.

Chris Fraker This depends on the oscillator strengths. Weak oscillators lead to peaks that show linear changes with volume fraction. The stronger the oscillators are, the more they deviate from Beer's approximation and the peaks shift to the red with increasing volume fraction. Read the whole story under Article Beyond Beer’s Law: Quasi-Ideal Binary Liquid Mixtures

For quantitative information regarding functional groups, the spectra should be pre-processed. Sample and reference taken should be uniform composition in volume/ weight. Then the band area of the functional group can be used for quantitative measurement provided the standard/ reference sample is provided.

If the %Transmittance at particular wavenumber is 30 and for another sample, it is 80 at same wavenumber, then what inference we can have? Can we quantify the concentration?

As we know that Transmittance is inversely proportional to absorbance and absorbance is directly proportional to concentration. If we can quantify it, then what is the formula? Kindly mention the name of the software if any?