Hey.  Using Drift IR is not the best way to quantity Lewis and bronsted acid sites. The best way is thé use of dynamic vacuum setup 

Thanks

Dear Colleague Wickramaratne,

1- The total number of acidic sites (sites. m-2) over each catalyst can be measured using the temperature programmed desorption of pyridine (TPD-pyridine) as the probe molecule. The details have been described in previous publication (attached).

The acidity populations over the surface of catalysts, under investigation, were measured thermogravimetrically using the adsorption of pyridine as probe molecule. Small portions (50mg) of each sample were pre-heated at 250°C for 2 h in air before the exposure to the probe molecule. 15-20 mg of pyridine–covered samples were subjected to TG analysis on heating up to 600°C (at 20°C/min heating rate) in dry N2 (flow rate = 40 ml/min). The mass loss due to desorption of pyridine from the acidic sites, was determined as a function of total surface acidity as sites.g-1cat.

2- To detect the Bronsted acidic sites, you can use 2,6-dimethylpyridine as a probe of the strength of Brønsted acid sites.

Finally if subtracted the number of acidic sites of step 2 (Brønsted only) from step 1 (Lewis +Bronsted), you can get the number of Lewis acidic sites

However, FTIR- Pyridine is only used to distinguish between the Lewis and Brønsted

Hope this helping

Have a very good day