色谱分析条件对低纬度痕量长链烯酮温度指标应用可靠性的影响

通过对气相色谱仪分析低纬陆架痕量长链烯酮过程中的升温速率和载气流速两个主要条件进行了探讨,对比了不同的程序升温速率和不同载气流量条件下烯酮的分离效果和检测精确度及重现性。研究发现色谱分析条件对低纬度痕量长链烯酮的分析有显著的影响。当前广泛适用于中低纬度开放大洋沉积物样品的较高的程序升温方法难以对低纬度高陆源物质冲淡作用影响下的陆架海沉积物样品进行有效的分离分析。在接近U3K7′指标适用温度上限且C37∶3烯酮含量极低的情况下(1ng/g干样,计算温度接近27℃),采用较低的程序升温速率分离C37∶3和C37∶2及后续化合物有利于获得良好的分离效果,且分析的精确度和重现性较之高的升温速率好。在对痕量且接近温度适用极限的烯酮样品进行分析时,应采用相对较小的载气流量以便获得理想的分离度和更加精确的分析结果。

CHROMATOGRAPHIC QUALIFICATIONS AND THEIR EFFECTS ON RELIABILITY OF LOW-LATITUDE TRACE LONG-CHAIN ALKENONE AS A TEMPERATURE INDICATOR

Two main chromatographic qualifications,programmed temperature mode and carrier gas flow rate,were investigated for the analysis of trace alkenone from low-latitude continental shelf samples.The separability,test precision and repeatability under various gas chromatographic(GC) analytical circumstances were discussed.Our results show that chromatographic qualifications have great impacts on the analysis of those trace alkenone.Traditional high GC programmed temperature ramps(PTR),which are adequate for ocean sediment samples,were confirmed no longer applicable for the analysis of the shelf samples highly diluted by terrigenous debris.Excellent separabilities for C37∶x(C37∶2 & C37∶3) and the homolog compounds were obtained under Low PTR condition(1.3℃/min at high temperature stage),even for the samples in which the C37∶3 alkenone content is extremely low(1ng/g dry sediment,calculated sea surface temperature is near to 27 ℃).Furthermore,the test precision and repeatability are much better under low PTR.Our results also indicate that perfect separabilities and test precision are likely to be obtained under low carrier gas flow rate for those shelf sediment samples with low trace alkenone content.