A comparison of polymeric materials as pre-concentrating media for use with ATR/FTIR sensing

Polymer-modified ATR-FTIR spectroscopy was investigated to determine its potential suitability for use as an analytical methodology for process stream analysis. The process stream under investigation contains toluene, tetrahydrofuran, ethanol, and acetonitrile in an aqueous matrix. Four polymers, Teflon (R) AF2400, poly(acrylonitrile-co-butadiene) (PAB), polydimethylsiloxane (PDMS), and poly(styrene-co-butadiene) (PSB), were chosen for study based on partition coefficients measured using a novel automated GC technique. Polymer suitability as pre-concentration media was assessed utilizing analyte/polymer diffusion coefficient data, equilibrium absorbance values, water ingress, and polymer plasticization. PAB displayed the fastest sensing times and enhanced sensitivities. Teflon (R) AF2400 demonstrated a low water absorption and a low degree of plasticization. Other factors affecting the diffusion rate of analytes were also investigated including molecular size, shape and analyte concentration. This research demonstrated that the choice of pre-concentrating medium is not a trivial issue, being dictated by a combination of sensitivity constraints as well as polymer robustness in real sample matrices.