Solid-phase extraction and capillary electrophoresis determination of phenols from soil after alkaline CuO oxidation Original Research Article

Alkaline CuO oxidation has been used on molecular-level analyses of phenols from organic matter in the last decades. This method, originally developed by Hedges and Ertel [Hedges, J.I., Ertel, J.R., 1982. Characterization of lignin by gas capillary chromatography of cupric oxide oxidation products. Anal. Chem. 54, 174–178] has several drawbacks that have limited is wider utilization. In this paper, we propose a modification of the method using a solid-phase extraction (SPE) instead of a liquid–liquid extraction. The SPE procedure using C18 cartridges was optimized to obtain high recoveries. The sequential elution with acetonitrile and methanol was found to be the most appropriate procedure. Recoveries of the 12 phenols in individual standard solutions ranged from 84% to 113% with relative standard deviation (RSD) lower than 12%. Experiments with a mixed standard solution highlighted the competition between the different phenols for the adsorbing sites. Recoveries decreased with polarity, reaching 30% for p-hydroxybenzoic acid when present at a concentration of 2.5 × 10−3 M.