University of the Basque Country, Department of Analytical Chemistry, P.O. Box 644 E-48080, Bilbao, Basque Country, Spain.
J Chromatogr A. 2011 Mar 25;1218(12):1656-62. doi: 10.1016/j.chroma.2010.11.034. Epub 2010 Nov 26.
The analysis of organic biomarkers in chert samples offers key information about the environmental conditions in which these samples were formed, and this information can be used to track the lithic materials of many archaeological artifacts. Since the content of the organic fraction is very low and the complexity of the organic extracts is quite high, we have optimized the GC×GC separation of these mixtures. Making use of mixture of C(16)H(34)-C(44)H(90)n-alkane standards, a central composite design was carried out taking into account the carrier flow in the first and second columns, the modulation period and the discharge time. Regarding the measured responses, though the initially considered one was the peak volume, we have also evaluated the effects on the number of modulated peaks per analyte, the symmetry of the modulated peaks and the number of detected compounds. The final optimum conditions were defined as follows: a hydrogen flow of 1.2 mL/min in the first column and 18 mL/min in the second one, a modulation period of 1.4 s and a discharge time of 0.1 s and under these conditions all the response variables showed optimum values. Based on this optimized method several chert samples obtained from different stratigraphic levels in an ancient quarry were studied and we were able to distinguish them on the basis of the different constituents of organic biomarkers, such as mono-methylated alkanes, cyclic n-alkanes, branched alkanes, steranes and hopanes.
对燧石样本中的有机生物标志物进行分析，可以提供有关这些样本形成时环境条件的关键信息，这些信息可用于追踪许多考古文物的石器材料。由于有机部分的含量非常低，且有机提取物的复杂性相当高，因此我们对这些混合物的 GC×GC 分离进行了优化。利用 C(16)H(34)-C(44)H(90)n-烷烃标准混合物，在考虑第一和第二柱载气流、调制周期和放电时间的情况下进行了中心复合设计。关于测量的响应，尽管最初考虑的是峰体积，但我们还评估了对每个分析物的调制峰数、调制峰的对称性和检测到的化合物数的影响。最终的最佳条件定义如下：第一柱的氢气流量为 1.2 mL/min，第二柱的氢气流量为 18 mL/min，调制周期为 1.4 s，放电时间为 0.1 s，在这些条件下，所有响应变量均显示出最佳值。基于这种优化方法，对从古采石场不同地层获得的几个燧石样本进行了研究，我们能够根据有机生物标志物的不同成分（如单甲基烷烃、环状烷烃、支链烷烃、甾烷和藿烷）对它们进行区分。
