EVALUATION OF CHLOROPARAFFIN PVC PHASES FOR ATR FT-IR ANALYSES/

A significant limitation to the use of ATR/FT-IR analysis for aqueous solutions is the relatively high bulk concentration of analyte that is required. One approach to improving the detection of an analyte is to incorporate a thin polymeric phase at the surface of the ATR element. The purpose of the polymeric phase is to extract the analyte of inter est and concentrate it within the depth of penetration of the evanesce nt wave. With the use of a very high molecular weight polyvinyl chlori de phase, the time necessary to reach equilibrium for a 0.05% (v/v) ni trobenzene in a 1.5% (w/v) methanol/vater solution was over 60 min. A study was undertaken to determine whether incorporating a chloroparaff in plasticizer into the polymeric phase would reduce the time required to reach the maximum level of absorbance achieved for the analyte. Sp ecifically, the ability of phases which are mixtures of PVC and chloro paraffin plasticizers to concentrate the analyte from aqueous solution s has been investigated. The results indicate that incorporating chlor oparaffin into a PVC phase reduces the time required to reach the maxi mum absorbance for the analyte in an aqueous solution containing 1.5% methanol by approximately 45%. The addition of chloroparaffin also res ults in an increase in the magnitude of absorbance observed for the an alytes investigated in this study.