Extractive sampling methods to improve the sensitivity of FTIR spectroscopy in analysis of aqueous liquids

Several methods of extractive sampling based on solvent elimination have been used to determine the concentration of different substances such as a sugar and a volatile organochloride in aqueous solutions. A dry extract technique based on the use of thin microporous polyethylene films as sample support has been evaluated in comparison with the direct transmission measurement through the liquid samples. Afterwards the Attenuated Total Reflection (ATR) on ZnSe and Ge crystals with a polymer coating has also been tested. The highest signal-to-noise ratio was obtained with the dry extract technique for the determination of a non volatile sugar. On the other hand, the best signal, lowering the detection limits to the low ppm concentrations, was obtained with the liquid extractive sampling (LES) method using a polymer coating on an ATR crystal for the determination of organochlorides.