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

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 ∆ 14C 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 twodimensional 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 ∆ 14C 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 ∆ 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.Higher-plant derived organic carbon represents a significant fraction of the earth's annual primary productivity and is also an important reservoir of fixed carbon, both living and dead. Organic matter (OM) derived from higher plants in terrestrial ecosystems can be processed to soil debris or converted to carbon dioxide through respiration. Once in aquatic ecosystems, such as rivers, more biological processing occurs as plant-derived OM makes its way to the ocean. Once in the ocean, it can be further transformed in the marine dissolved and particulate organic carbon pools, buried in coastal marine sediments, or converted to carbon dioxide. Traditionally, the radiocarbon age of bulk carbon in terrestrial reservoirs is used to infer the average age of mobilized organic carbon. For example, measurements of the ∆ 14 C of bulk particulate organic carbon (POC) and dissolved organic carbon (DOC) suggest that local geology and in situ biological production determine the average age of organic matter in rivers.1-5 Still, terrestrial carbon is a complex mixture that integrates recent biological and ancient geological carbon sources into a complex mixture of carbon-based materials at various stages of decomposition. More in-depth knowledge about the age of various carbon sources can tell us how carbon from different sources is processed. The advent of compound-specific radiocarbon analysis (CSRA) has presented the possibility of measuring the age of individual components within complex mixtures of organic carbon.6,7 Some researchers have used the ∆ 14 C value of long chain fatty acids in river delta sediments to apportion sources of organic matter and, therefore, to understand the fate ...

Age of riverine carbon suggests rapid export of terrestrial primary production in tropics

“…Lignin phenols were purified using high‐performance liquid chromatography, and ∆ 14 C values were obtained following Ingalls et al . []. Between 22–35 and 5–14 injections in reverse and normal phase, respectively, were required to obtain adequate material for 14 C‐AMS analysis.…”

“…An aliquot of each sample was quantified by gas chromatography flame ionization detection [Goni and Montgomery, 2000]. Lignin phenols were purified using high-performance liquid chromatography, and Δ 14 C values were obtained following Ingalls et al [2010]. Between 22-35 and 5-14 injections in reverse and normal phase, respectively, were required to obtain adequate material for 14 C-AMS analysis.…”

The Chemical Ecology of Soil Organic Matter Molecular Constituents

“…Used to monitor microbial activity with simulated soil temperature increases (Feng and Simpson, 2009). 2010; Ingalls et al, 2010). For example, compound specific isotope analysis (CSIA) has been used to measure the turnover and dynamics of SOM components in disturbed systems where new soil carbon inputs carry a distinct 13 C isotopic signature as compared to that of native (older) soil OM.…”

Muddy Waters: Unintentional Consequences of Blue Carbon Research Obscure Our Understanding of Organic Carbon Dynamics in Seagrass Ecosystems

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