Pueblo Bonito

Samples:
"Recent University of New Mexico re-excavation of trenches originally dug in the trash middens directly south of Pueblo Bonito in the 1920s recovered hundreds of thousands of fragmentary artifacts. For this analysis, we selected sherds from these contexts representing 5 different vessels that were either cylinder jars or pitchers. Three were characterized as probable cylinder jars, one as a definite pitcher, and one as an indefinite cylinder jar/pitcher.The selected sherds date between A.D. 1000 and 1125 based on decorative styles." (Crown and Hurst 2009:2110)

Analysis:
"The results of the HPLC MS confirmed the existence of theobromine in 3 of the 5 samples analyzed. These 3 samples were those characterized as probable cylinder jars. The sherds from the pitcher and indefinite cylinder jar/pitcher did not show the peaks characteristic of theobromine. Peaks from the extract of the residue from Sample 2001 were evident in the mass spectrum of the sample (Fig. 2), which confirms the existence of theobromine." (Crown and Hurst 2009:2111)

In the Washburn et al. (2011) chemical analysis, theobromine and theophylline were recorded when the "substance was present at 5 ng/mL or higher. At concentrations less than 5ng/mL, signal noise precluded detection with confidence" and "the same convention applies to caffeine except that the quantification limit was 10 ng/mL" (Washburn et al. 2011, Supplementary Material).