Sampling and Analysis of the Atmosphere Surrounding an Egyptian Mummy
The Department of Antiquities Conservation of the J. Paul Getty Museum recently requested assistance from CAS’ Simi Valley Air Quality Laboratory to sample and analyze the atmosphere surrounding a second century Egyptian mummy. About six years ago, the mummy was sealed in a case containing ambient air. The museum wished to determine the volatile and semivolatile organic compounds off-gassing from the mummy. One purpose of the study was to determine the impact of off-gassing on other artifacts that were to be displayed with it.
Compounds of interest included low molecular weight organic acids, volatile organic chemicals, and the semivolatile compound, guaiacol. Guaiacol is a component of cedar oil and one of the embalming fluids used by the Egyptians.The other chemicals were associated with previous restoration activities with the mummy.
In order to collect the samples, two holes were drilled in the case housing the mummy. Sampling ports consisting of Teflon tubing (1/4” OD) and a ferrule and female Swagelok fitting were installed in the holes. The ports were sealed off at the time of installation and only opened during sampling periods.
Two sampling and analytical methods were used to address the compounds of interest. Volatile organic compounds were sampled in evacuated passivated stainless steel canisters (SUMMA-like) and then analyzed for tentatively identified compounds (TICs) by gas chromatography/ mass spectrometry (GC/MS) following US EPA Method TO-15. This technique involves identifying the most predominant compounds by Jeanette Campbell – Simi Valley, CA in the sample by comparing their mass spectra with those from the NIST library, which contains mass spectra from more than 120,000 compounds. Heavier compounds were sampled on Tenax TA tubes and then thermally desorbed and analyzed by GC/MS following EPA Method TO-17. These samples were analyzed for guaiacol and other TICs, including acetic acid.
Compounds of both biogenic (e.g., isobutyric acid) and synthetic origin were identified in the samples (see Figure 1 on page 3). Acetaldehyde, 3-methylbutanal, pentanal, furfural and methyl methacrylate were present above their odor threshholds. Several of these compounds had an “odor character,” that might have contributed to the “characteristic mummy odor” described by one of Getty’s researchers.
An important outcome of this project was the side-by-side comparison of the efficacy of two sampling methodologies that are frequently used to evaluate organic compounds in indoor air investigations. Neither media type collected the full range of compounds of interest. Lighter compounds were only detected in the SUMMA-like canister sample. In contrast, heavier, higher boiling point compounds were only identified in the samples collected on the Tenax sorbent tube. Midrange compounds (e.g., boiling points of 70oC to 240oC) were detected using both sampling media and showed similar quantitative and qualitative results.
Although boiling point appeared to be the primary determinant of the compounds that were collected by the two types of media, other properties (vapor pressure, polarity, lability) may also have had an impact. For example, the labile compound, isobutyric acid, was only detected in the solid sorbent samples even though its boiling point (155o C) is in the more volatile range, which may be collected by SUMMA canisters.
The Mummy project presented the laboratory with a unique opportunity to evaluate an environment containing a wide range of compounds. The results of this project suggest that for indoor air investigations, the use of multiple sampling media may generate more meaningful data than reliance on a single type.
CAS would like to thank Cecily Grzywacz, Scientist in the Science Department of the Getty Conservation Institute and Marie Svoboda, Associate Conservator of Antiquities at the J. Paul Getty Museum for allowing us to present the results of their project.
Tags: Ambient Air, Department of Antiquities Conservation, Egyptian, Egyptian mummy, Getty Museum, Guaiacol, mummy, semivolatile organic compounds, SUMMA canisters, Teflon tubing, the mummy, TO-15, VOC