Investigation of Different Polymers as Coating Materials for IR/ATR Spectroscopic Trace Analysis of Chlorinated Hydrocarbons in Water

Abstract

Polymer-coated attenuated total reflection (ATR) elements have been used to compare the diffusion behavior and enrichment from aqueous solutions of three different chlorinated hydrocarbons (CHCs) — monochlorobenzene (MCB), chloroform (CF), and tetrachloroethylene (TeCE)—into different polymers. The influence of polymer properties such as glass transition temperature and crystallinity and the effect of the polymer background IR absorption and varying thicknesses of the polymer membranes to the detectability were investigated. The crystallinity and the glass transition temperature have a very pronounced influence on the velocity of the diffusion process, whereas the partition coefficient influences the amount of CHC diffusing into the polymer membrane. The time constants for 90% saturation of the polymer with the test analytes are in the range of 8 to 40 min, depending on the nature of the polymer and analyte. A linear calibration graph was obtained for simultaneous detection of all three test analytes in the range from 5 mg/L to 100 mg/L CHC with detection limits of 1.5 to 2 mg/L. Coefficients for CHC partitioning between water and polymers measured by ATR/IR were in good agreement with values determined by GC/MS.