## 3 Results and Discussions  
### Chromatographic Considerations and Sample Analysis  
Data processing revealed anywhere from 200 to 2000 features identified within a sample. Figure 1 shows a variety of chromatograms obtained using the Rtx-5 MS \(\times\) Rxi-17 Sil MS column set. The resin samples yielded the most complex volatile signature of all sample types analyzed. Resin is an important substance in archaeological research as it has been used during prehistory as an adhesive to half stone tools [9; 30]. Hafting is considered an invention that revolutionized stone tool use [30; 31] and that necessitated abstract thought and planning [9; 32]. Therefore, being able to understand the mode of preparation allows an understanding of the cognitive and technical capabilities of their makers [33]. Figure 1 (top left and top right) demonstrates the ability to differentiate the volatile signature of the two resin and bees wax mixture samples based on different preparation methods differentiated by heating length. It, therefore, follows that it may be possible, given a larger database of controlled study information, to provide more information in the future about the type of resin discovered on an archaeological tool and its potential mode of preparation. Figure 1: Selected total ion current (TIC) contour plots from six samples analyzed on the Rtx-5 MS \(\times\) Rxi-17 Sil MS column set. The sample of mixed sediment and bone displayed in Figure 1 also yielded a complex profile (middle left). This sample exhibited numerous hydrocarbon compounds, leading to a need for more effective optimization of the first dimension separation. There were only few trace compounds that eluted separately along the second dimension axis, suggesting that a well-optimized 1D GC-MS method may be useful in screening sediment samples if bone fragments are suspected to be contained in them (_i.e._, differentiation of sediment from sediment mixed with bone). However, this GC\(\times\)GC-TOFMS method had added value in providing a \"total screening\" approach, in that the same method could potentially be applied to a vast array of potential unknown residues to provide information about sample characteristics. In an archaeological context, due to the minimal amounts of samples available it may not be possible to distinguish visually (or microscopically) between a sediment sample and other possible organic residues. A total screening approach can be valuable from an investigative standpoint and when processing a large number of samples from an archaeological site. In addition, comparing results from sediment samples and extractions from stone tools can help in distinguishing between residues that can be linked to the use of a specific stone tool and residues that occur on a more general level throughout the site. The signature from a minimal amount of sediment washed from an archeological stone tool also yielded a volatile signature different than that from the mixed sediment and bone sample. In this situation, the number of components in the volatile signature was fewer but there was a higher need for the selectivity of GC\(\times\)GC-TOFMS due to the fact that more compounds separated along the \({}^{2}\)D axis. The samples of ivory, bone, meat/starch, antler, meat/starch/blood, and leather generated minimal signals that could not be visually differentiated from blank vials without further testing. This could be due to the fact that no volatile compounds existed in the samples that were available for SPME extraction. It could also be due to the fact that a longer or warmer SPME extraction was required to release characteristic volatiles from these matrices. In addition, obtaining experimental replicates would allow for the generation of statistics that could assist in determining whether a peak is discriminatory for that sample type, and therefore would lead to more robust determinations of compound importance.