When a fouled membrane like Nafion was analyzed for FTIR analysis, before mesurment should we remove the flock (layer of bacterial biofilm) on the membrane or not? For the assessment of membrane fouling?
If you can remove the fouling layer and measure its FTIR independently you will get richer information on the chemical composition not disturben by the Nafion membrane. Alternatively, if you use ATR, you can try to compare the ATR-FTIR spectra of the foulde and non-fouled layer. As ATR is surface sensitive (in the order of microns), you will get a fairly surface specific response if you attach the fouled surface to the ATR crystal. Watch however, the water-solubility of the crystals!!!! You may try to dry the membrane first, as water interferes with the spectra.