An Optimized Analytical Method to Quantify Pyrogenic Carbon Using Benzene Polycarboxylic Acids in Marine and Lacustrine Samples

Abstract

Summary Benzene polycarboxylic acids (BPCAs) have been used as molecular markers to quantify and characterize pyrogenic carbon (PyC) in complex samples. The existing analytical procedures to generate and quantify BPCAs are time-consuming and cannot be used to analyse a large number of samples. Here, we present an optimized methodology to quantify BPCAs in marine and lacustrine samples. It involves a multi-step procedure that includes the oxidation of the aromatic structures of the PyC to generate the BPCAs using a microwave-assisted acid digestion, reducing oxidation time 4 times over the conventional methodology. Interfering cations (Fe) were removed with a cation exchange resin using 40% methanol as a solvent elution. The sensitivity and selectivity of the analysis was greatly improved by using HILIC chromatography coupled to tandem mass spectrometry using an electrospray interface. The sensibility and reproducibility of this method was evaluated using the method of standard addition of individual BPCAs compounds in marine samples. In addition, we have appraised our methodological approach and the use of BPCAs as proxies of wildfire occurrence and magnitude using set surface sediments from Spanish lakes and wildfire database spanning 5 decades.