NMR and GC/MS analysis of industrial chloroparaffin mixtures

Jannik Sprengel,Walter Vetter

doi:10.1007/s00216-020-02720-7

Abstract

Chlorinated paraffins (CPs) are high-volume chemicals used worldwide in various industries as plasticizers, lubricants, and flame retardants. CPs are produced by chlorination of alkane mixtures which leads to complex products of thousands of homologs and congeners. Classic mass spectrometric analyses of CPs allow determining carbon chain lengths and degrees of chlorination while information on the substitution patterns cannot be derived. Therefore, we performed different one- and two-dimensional nuclear magnetic resonance spectroscopy (NMR) experiments, elemental analysis (EA), and gas chromatography coupled with electron capture negative ion mass spectrometry (GC/ECNI-MS) for the analysis of ten technical CP products with 42%, 52%, and 70% chlorine content from four producers. Slight differences in chlorine content but varying chain length compositions were observed for similarly labeled products from different manufacturers. Two-dimensional heteronuclear spectral quantum coherence (HSQC) measurements helped to evaluate ten structural elements in the products and confirmed the presence of geminal chlorine atoms in primary and secondary carbons in products with 70% chlorine. The variation of signal groups increased with increasing chlorine content of the products. Two-dimensional heteronuclear multiple bond coherence (HMBC) analysis of one sample and GC/ECNI-MS measurements indicated the presence of impurities (e.g., C9-CPs, iso-alkanes) in different technical CP products. These methods could in future allow for better distinction of CP mixtures, and an improved trace-back of environmental CPs to the source, based on specific structural features. Additionally, further structural characterization could help in the development of more accurate analysis processes.Graphical

Highlights

Produced since the 1930s, chlorinated paraffins (CPs) are usually described as complex mixtures of polychlorinated n-alkanes which differ in chain length composition and degree of chlorination [1]
Samples B-52 and D-52 contained ~ 4% and ~ 8% SCCPs. These five MCCP products were dominated by C14-CPs (38.5–66.6%), which is in accordance with the general prevalence of C14-CPs among MCCPs in the environment [12], CP containing products [33], and a previously analyzed technical CP-52 product [34]
The technical CP-42 and CP-52 products analyzed in that study were dominated by C13-CPs, which was different to our samples

Summary

Introduction

Produced since the 1930s, chlorinated paraffins (CPs) are usually described as complex mixtures of polychlorinated n-alkanes which differ in chain length composition and degree of chlorination [1]. In China alone, more than 1 million tons of CPs is currently produced per year [2]. Applied as additives, these lipophilic and persistent chemicals can be released from products in which they are used. Some studies already have examined homolog compositions (mainly SCCPs) in technical CP products from China [11,12,13,14]. The chemical structure of halogenated compounds has an influence on their instrumental response behavior [17].

Methods

Results

Conclusion