HPLC Purification of Higher Plant-Dervied Lignin Phenols for Compound Specific Radiocarbon Analysis

Anitra E Ingalls,Erin E Ellis,Laura Truxal,Ellen R M Druffel,Kelsey E Mcduffee,Guaciara M Santos,Richard G Keil

doi:10.1021/ac1016584

Anitra E Ingalls, Erin E Ellis + Show 5 more

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https://doi.org/10.1021/ac1016584

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Journal: Analytical Chemistry	Publication Date: Oct 1, 2010
Citations: 31	License type: cc-by

Affiliation: University of California, Irvine

Abstract

The ability to measure the radiocarbon content of compounds isolated from complex mixtures has begun to revolutionize our understanding of carbon transformations on earth. Because samples are often small, each new compound isolation method must be tested for background carbon contamination (C(ex)). Here, we present a new method for compound-specific radiocarbon analysis (CSRA) of higher plant-derived lignin phenols. To test for C(ex), we compared the Δ(14)C values of unprocessed lignin phenol containing standard materials (woods, leaves, natural vanillin, and synthetic vanillin) with those of lignin phenols liberated by CuO oxidation and purified by two-dimensional high-pressure liquid chromatography (HPLC) coupled to mass spectrometry (MS) and UV detection. We assessed C(ex) associated with (1) microwave assisted CuO oxidation of bulk samples to lignin phenol monomers, (2) HPLC purification, and (3) accelerator mass spectrometry (AMS) sample preparation. The Δ(14)C of purified compounds (corrected for C(ex)) agreed, within error, with those of bulk materials for samples that were >10 μg C. This method will allow routine analysis of the Δ(14)C of lignin phenols isolated from terrestrial, aquatic, and marine settings, revealing the time scale for the processing of one of the single largest components of active organic carbon reservoirs on earth.

Highlights

To test for Cex, we compared the ∆14C values of unprocessed lignin phenol containing standard materials with those of lignin phenols liberated by CuO oxidation and purified by twodimensional high-pressure liquid chromatography (HPLC) coupled to mass spectrometry (MS) and UV detection
The greatest challenge in carrying out small scale compound-specific radiocarbon analysis (CSRA) from complex mixtures is maximizing the quantity of the compound of interest that is purified while minimizing the quantity of background carbon contamination or exogenous carbon (Cex) that is added to the sample during purification and subsequent processing
In order to assess the size and ∆14C of Cex associated with microwave assisted CuO oxidation and HPLC purification of lignin phenols, we carried out 14C analyses of homogeneous bulk standard materials and individual compounds isolated from those bulk materials

Summary

Introduction

R. M.; Xu, X.; Zhang, D.; Trumbore, S.; Eglinton, T. Purified compounds on which ∆14C values are measured (∆14Cmeasured) contain carbon from several sources including: carbon from the sample or compound of interest (Csample), carbon introduced during chemical processing such as the microwave (Cchemistry), carbon introduced during HPLC purification (CHPLC), and carbon introduced during AMS sample preparation, e.g., combustion, graphitization, and graphite target handling (CAMS).

Results

Conclusion