Determination of methoxy groups in soils by the Zeisel method combined with gas-liquid chromatography

Gas-liquid chromatography combined with hydriodic acid digestion has been used to determine methoxy groups in soil. Finely ground soil is boiled with hydriodic acid under reflux for 30 min using 1-iodobutane as an internal standard, and the iodomethane formed is extracted with carbon tetrachloride. The gas chromatographic analysis of the extract is rapid with complete resolution of all the peaks within a total retention time of 1.5 min. The method is sensitive and precise, and gives accurate results for pure compounds and pure compounds added to soil. Analysis of a range of soils gave results that were consistent with published data. The method is suitable for the analysis of whole soil, for fractions of soil organic matter or for pure compounds.