INVESTIGATION OF DIFFERENT POLYMERS AS COATING MATERIALS FOR IR ATR SPECTROSCOPIC TRACE ANALYSIS OF CHLORINATED HYDROCARBONS IN WATER

Polymer-coated attenuated total reflection (ATR) elements have been us ed to compare the diffusion behavior and enrichment from aqueous solut ions of three different chlorinated hydrocarbons (CHCs)-monochlorobenz ene (MCB), chloroform (CF), and tetrachloroethylene (TeCE)-into differ ent polymers. The influence of polymer properties such as glass transi tion temperature and crystallinity and the effect of the polymer backg round IR absorption and varying thicknesses of the polymer membranes t o the detectability were investigated. The crystallinity and the glass transition temperature have a very pronounced influence on the veloci ty of the diffusion process, whereas the partition coefficient influen ces the amount of CHC diffusing into the polymer membrane. The time co nstants for 90% saturation of the polymer with the test analytes are i n the range of 8 to 40 min, depending on the nature of the polymer and analyte. A linear calibration graph was obtained for simultaneous det ection 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 part itioning between water and polymers measured by ATR/IR were in good ag reement with values determined by GC/MS.