毛细管气相色谱法测定凋落物淋洗液中的低分子有机酸

Determination of Low Molecular-weight Organic Acids in Litter Leachates by Capillary Gas Chromatography

以我国东北林区重要树种落叶松(Larixolgensis)、水曲柳(Fraxinus mandshurica)、红松(Pinus koraiensis)和白桦(Betula platyphylla)凋落物淋洗液为材料,建立了一种森林凋落物淋洗液中低分子有机酸测定的毛细管气相色谱法。凋落物淋洗液经冷冻干燥,用H2SO4∶CH3OH溶液浸提低分子有机酸,并同时密封60℃甲酯化24h,用CHCl3萃取后,进行毛细管气相色谱分析。实验表明,样品冷冻干燥处理,密闭条件下采用甲醇浸提的同时直接进行甲酯化反应,有效避免了传统方法浓缩和酯化过程中易挥发有机酸的损失,且酯化完全;选择性好,能同时测定多种低分子有机酸;所测的8种低分子有机酸,经回收率、精密度和检出限等可行性检验,是一种凋落物淋洗液样品中低分子有机酸分析测定的可靠方法。

A capillary gas chromatography procedure was established to determine low molecular-weight organic acids in litter leachates from Larix olgensis, Fraxinus mandshurica, Pinus koraiensis and Betula platyphylla forests in northeast China. First, the litter leachates were dried by freeze-drying method, next low molecular-weight organic acids were lixiviated and derived into corresponding esters with H2SO4∶CH3OH at 60 degrees C for 24 hours, and then extracted in CHCl3 and analyzed by capillary gas chromatography system. Results showed that the freeze-drying samples and the esterification with CH3OH occurred while extracting low molecular-weight organic acids with the same reagent could reduce volatilization loss of low-molecular-weight organic acids in the course of condensation and esterification when the conventional method was used to determine organic acids. Moreover, good selectivity was obtained, and different kinds of low-molecular-weight organic acids could be determined simultaneously and accurately. Feasibility test of recovery, relative standard deviation, and the lowest detection limit proves that it is a reliable method for determining low molecular-weight organic acids in litter leachates.