Elsevier

Journal of Chromatography A

Volume 1370, 28 November 2014, Pages 1-8
Journal of Chromatography A

Method development for simultaneous analyses of multiple legacy and emerging organic chemicals in sediments

https://doi.org/10.1016/j.chroma.2014.10.031Get rights and content

Highlights

  • Laboratory procedure to analyze multi-groups of organics in sediment was developed.

  • Cleanup/fractionation using both alumina and silica is more effective than silica.

  • Effects of using strong acid, base and copper on analyte recoveries were discussed.

  • The method was validated using spiked and standard reference sediments.

Abstract

The objective of this work was to investigate the feasibility of using a single pretreatment procedure for the analyses of multiple groups of organics, which have a wide range of chemical structures and physicochemical properties, in sediment samples. Nine groups of 162 individual compounds (including 11 surrogates) were investigated, including polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), polychlorinated biphenyls (PCBs), polychlorinated diphenyl ethers (PCDEs), polychlorinated naphthalenes (PCNs), organochlorine pesticides (OCPs), polybrominated diphenyl ethers (PBDEs), novel halogenated flame retardants (nXFRs), musk fragrances (MFs) and organophosphate flame retardants (OPFRs). The individual and grouped recoveries of spiked analytes from adsorption chromatographic columns using either only fully activated, neutral silica gel (SG) or the combinations of silica gel and alumina (Si/Al) sorbents were compared. The results showed a generally stronger adsorption and more effective fractionation on the Si/Al column than on the SG column. The dependence of fractionation on halogen substitution, molecular planarity, and polar functional groups was discussed. The effects of adding sulfuric acid with two different methods were investigated, and the recoveries of a number of MFs, OCPs, nXFRs and OPFRs were recovered less than 60%. Sodium hydroxide treatment of silica gel had minor effects on some OPFRs. Copper used to remove elemental sulfur did not affect the recoveries of all target analytes except chloroneb. The finalized method was validated by spiking the target analysts into the sediment samples and comparing the analytical results of this work on two standard reference materials for sediment (SRMs 1941b and 1944) with the certified or reference values.

Introduction

The number of chemicals registered in the Chemical Abstracts Service (CAS) Registry of the American Chemical Society is approaching 89 million [1]. For North America, 610 organic substances were prioritized for environmental surveillance; only <50 of them have been routinely monitored due to limited resources [2]. Indeed, the analyses of chemical contaminants in environmental matrices are tedious and costly, involving major steps of extraction, cleanup, and instrumental analysis. These procedures were often developed targeting one class of analytes, therefore cannot meet the need of monitoring a rapidly increasing number of pollutant chemicals in the environment.

Advancements in mass spectrometry (MS) in recent decades have brought about unprecedented selectivity and sensitivity in the detection and quantification of chemical substances. This was thought to lessen the demand on fractionation/cleanup process, which is the most labor-intensive step in sample pretreatment. However, this may not be true when the interfering substances in sample extracts are rich and complex. Such substances contaminate the inlet of gas chromatography (GC) causing carry-over of the analytes, shorten the lifetime of GC columns, and compromise the MS sensitivity. This is particularly true for large volume injection which has become a common practice in trace level GC analyses. Effective fractionation and cleanup of the sample extracts not only abate such problems but also have the potential of obtaining multiple fractional samples which subsequently undergo different instrumental analyses. To this end, the classical adsorption chromatography using silica gel, alumina, and/or other adsorbents remains as the most effective method today.

The objective of this work was to examine the feasibility of using a single sample pretreatment procedure and multiple GC/MS runs for the analyses of multiple groups of semivolatile organics in sediment samples. The emphasis was on the development of fractionation/cleanup procedure using low pressure adsorption chromatography. A total of 162 individual analytes (including 11 surrogates) were analyzed covering chemical families of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), biphenyls (PCBs), naphthalenes (PCNs), and diphenyl ethers (PCDEs), polybrominated diphenyl ethers (PBDEs), novel halogenated flame retardants (nXFRs), organochlorine pesticides (OCPs), musk fragrants (MFs) and organophosphate flame retardants (OPFRs). To our knowledge, few previously published laboratory procedures involved such a wide range of analytes [3]. As such, the procedure developed in this work would be much more cost-effective compared with analyzing these analyte groups separately.

Section snippets

Chemicals

Chemical standards were purchased from AccuStandard (New Haven, CT), Wellington Laboratories (Guelph, Ontario, Canada), Cambridge Isotope Laboratories (Andover, MA), Toronto Research Chemicals (Toronto, Canada), and the Florida Center for Heterocyclic Compounds of University of Florida (Gainesville, FL). The target analytes are grouped in Table 1, and the individuals are listed in Table S1 of the Supplementary Materials (SM). The structures of analytes are given in SM Fig. S1.

All solvents were

Comparing silica gel and silica gel alumina columns

Table 2 compares the recoveries of all analyte groups from chromatographic fractionations using the SG and the Si/Al columns. The recoveries of individual analytes are summarized in Table S3, and are illustrated in Figs. 2 and S2 for the Si/Al and SG columns, respectively. Based on the two-sided equal variance t-test, the mean recoveries of the two methods are not statistically different (p > 0.05) for all groups except PBDEs and nXFRs (p < 0.05). These two groups as well as OPFRs were recovered

Conclusions

We developed a laboratory procedure for the analysis of a suite of organic pollutants with various chemical structures in natural sediment samples. The procedure includes ASE extraction, one step cleanup with four fractions collected, and multiple runs for individual or combined fractions using GC–QQQMS or GC–MS. This paper focuses on the optimization of the adsorption chromatographic cleanup and fractionation of the extract mixtures.

Adsorption column chromatography using combined silica gel

Acknowledgements

This research was part of the Great Lakes Sediment Surveillance Program (GLSSP) funded by a Cooperative Agreement from the U.S. EPA Great Lakes Restoration Initiative with Assistance No. GL-00E00538 (EPA Program Officer Todd Nettesheim). The first author was also supported by the Predoctoral Fellowship provided by the Institute for Environmental Science and Policy at the University of Illinois at Chicago.

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