Separation and characterization of humic acids from Antarctica by capillary electrophoresis and matrix-assisted laser desorption ionization time-of-flight mass spectrometry: Inclusion complexes of humic acids with cyclodextrins

A new capillary electrophoresis procedure based on micellar electrokinetic capillary chromatography for the separation of humic acids (HAs) isolated from Antarctica soil was developed. The HAs were separated and characterized using a background electrolyte containing 0.09 M borate+0.09 M Tris+0.001 M EDTA (BTE) of pH 8.3, modified with α-, β-, or γ-cyclodextrins (CDs) and sodium dodecyl sulfate. It was found that from alkaline solution of HAs in the presence of CDs, the HAs are not completely precipitated with a strong acid and a certain part (some fractions) remains soluble. Mass spectrometry shows that HAs contain 15–25 simple low-Mr compounds and several families of compounds with similar structure (m/z≈800–1200). Comparison of HA analysis from Antarctica soil with those of soil HAs from the American continent show a high similarity between the samples and confirm several identical compounds and some with very similar structural units.