真空冷冻干燥-稳定同位素比率质谱法测定土壤中水溶性有机碳同位素

Stable isotope analysis of dissolved organic carbon in soil using stable isotope ratio mass spectrometry coupled with vacuum freezing drying method

提供了一种可批量处理、消耗低廉的测定土壤水溶性有机碳同位素的新方法。该方法通过多水土质量比法提取土壤水溶性有机碳,得到含土壤水溶性有机碳的溶液,经磷酸酸化至pH小于2,将所得的溶液通过冷冻干燥进行浓缩,浓缩后的物质加高纯水复溶、在银舟中多次干燥富集后通过元素分析仪-稳定同位素比率质谱仪(EA-IRMS)进行δ^(13)C值测定。本方法中对多水土质量比法提取土壤水溶性有机碳的水土比例、振荡时间等参数进行了优化,将冷冻干燥的浓缩方式用于土壤可溶性有机碳同位素测定的前处理。通过土壤样品的平行测定对比,δ^(13)C的标准差小于0. 1‰,表明该方法重现性好,样品测试精密度高。

By means of a simple extraction with ultrapure water of air-dry soil samples,dissolved organic carbon was extracted.The inorganic carbon in extract was removed by adjusting the pH to less than 2 with H3PO4.The acidified extract was concentrated by vacuum freezing drying method.And the concentrate was re-dissolved in small amount of ultrapure water.Then the solution was dried in silver capsule for several times to accumulate enough dry mass,which can be determined by elemental analyser-stable isotope ratio mass spectrometry for δ^13C .The ratio (m/V)of soil to water and equilibrium time of extraction were optimized.It was noteworthy that the vacuum method was used for the pretreatment of dissolved freezing drying organic carbon in soft.The established method was applied to the analysis of δ^13C in soil samples.The standard deviation of six parallel determination results was 0.1‰.This showed that the established method was accurate and reliable.