Atmospheric Chemistry and Physics Comparison of analytical methods for Humic Like Substances

Abstract. Humic-Like Substances (HULIS) are a major contributor to the organic carbon in atmospheric aerosol. It would be necessary to standardize an analytical method that could be easily and routinely used for HULIS mea-surements. We present one of the first comparisons of two of the main methods in use to extract HULIS, using I) a weak anion exchanger (DEAE) and II) the combination of two separation steps, one according to polarity (on C18) and the second according to acidity (with a strong anion ex-changer SAX). The quantification is performed with a TOC analyzer, complemented by an investigation of the chemi-cal structure of the extracted fractions by UV-Visible spec-troscopy. The analytical performances of each method are determined and compared for humic substances standards. These methods are further applied to determine the water ex-tractable HULIS (HULISWS) and the 0.1 M NaOH alkaline extractable HULIS (HULIST) in atmospheric aerosol col-lected in an Alpine Valley during winter time. This compar-ison, although on a limited batch of samples shows that the simpler DEAE isolation procedure leads to higher recoveries and better reproducibility than the C18-SAX procedure, and might therefore be preferable.