Synthesis and Analysis of Chlorinated Paraffins as Reference Standards

Abstract

Persistent organic pollutants (POPs) are synthetic chemicals that persist in nature over time and lead to adverse effects towards humans and the environment. Due to their concerning properties, such as persistency, toxicity and bioaccumulation potential, these chemicals must be monitored and restricted to avoid cumulative concentrations in the environment. Consequently, during the Stockholm Convention of 2004, a treaty was signed to reduce or ban the production of POPs. Amongst the currently listed chemicals are a multitude of chlorinated pesticides and insecticides, short-chain chlorinated paraffins (SCCPs, C10-13), polychlorinated biphenyls and perfluorooctanoic acid. After receiving heavy restriction on their production and export, SCCPs were substituted with medium-chain chlorinated paraffins (MCCPs, C14-17) and long-chain chlorinated paraffins (LCCPs, C≥18). Higher concentrations of MCCPs and LCCPs were subsequently observed in the environment.

In order to enforce the Stockholm Convention, effective methods for monitoring the environmental concentrations of SCCPs are required. Furthermore, monitoring of MCCPs and LCCPs is highly desirable, given their candidate-status for classification as POPs. Analysis of chlorinated paraffins (CPs) is inhibited by both the enormous number of components present in the mixtures and the lack of suitable reference standards.

Through the four publications described herein, we sought to expand the methodology available for the production and analysis of constitutionally defined CPs. Moreover, we sought to synthesise reference standards that were more suitable for CP analysis than those already available. In publications I and II, we described the synthesis of constitutionally defined CP standards, including both non-isotopically enriched reference materials and 13C-labelled internal standards. During publication III we investigated the stereochemistry of the isomer mixture obtained after dichlorination of alkenes. Finally, publication IV encompassed one novel method to calculate the chlorine percentage of both complex and single-chain mixtures, as well as two further methods for calculating the chlorine percentage of single-chain mixtures, inspired by a pre-existing model.