For some chemists, the science is their first love and the lab is where all their work takes place. For Professor Ruth Ann Armitage at Eastern Michigan University, the application of chemistry to the field of archeology has led her outside the lab to work with museum curators and archeologists and back again with some unusual samples to analyze. In her archeological chemistry work she uncovers how people used ancient formulas and recipes in their daily lives and has answered numerous questions about a wide variety of artifacts. Simultaneously, as a professor she has also helped a new generation of students learn real-world applications and how to use all the analytical tools available to them.
Armitage utilizes her lab’s arsenal of tools, including her mass spectrometer, to answer much deeper questions than just the age of an item. In many archeological cases, carbon dating is the ultimate step, but, “It all comes back to understanding the organic composition of things in order to get better carbon dating,” she says. “Mass spec is revolutionizing archeological science, from small molecules to proteomics,” she says.
Her go-to mass spec for fast data is the JEOL AccuTOF™-DART®. “I always try it first, then like to follow up with FTIR and SEM, and we just got a Raman instrument and now I need to figure out how to do that, too.”
Armitage pioneers an aspect of mass spec analysis to probe for deeper answers. “Ruth Ann uses AccuTOF-DART as an ambient ionization tool box. She uses all the tricks and tools including inlet ionization to complement other techniques. No one technique does everything,” says Dr. Robert (Chip) Cody, co-inventor of DART and JEOL’s Mass Spectrometer Product Manager. Cody and Armitage have co-authored papers or worked together on experimenting with techniques, such as the time Armitage was asked to analyze blood on an ancient African mask. He delights in learning about her various projects that she has done with the direct analysis capability of the mass spec.
Most processes don’t really require sample prep before analysis, but depending on the sample, “a little bit of prep can help yield different information,” Armitage says. She explains that dyes are really hard to detect when analyzing ancient fibers from textiles, “but by treating the fibers with formic acid I was able to release them.
Additional techniques include coated blade spray and paper spray. “We’re analyzing some of the (fiber) dyes with Paper Spray™ – running the same sample by 3 or 4 different techniques. Everyone else does dyes with HPLC – it takes a long time and you get great information, but by DART it takes a whole lot less time.”
The versatility and quick answers are fun to show to colleagues and students. “When a retired colleague who used to run an analytical lab comes back to visit, he just loves to come and watch me run DART because he can’t believe how fast it is – it’s so exciting to see what we can do now.”
She first learned about the AccuTOF-DART from one of the earliest users in 2007, when she met Jeanette Adams at a conference. Adams was using the technique at the Library of Congress.
Her expertise in this type of analysis aids her in piecing together the story behind the artifacts. For example, “By looking at binding material, if you can figure out what that is it might tell us something about the people who used it, this really is where archeological chemistry come in – can we use the composition of material to tell us about the technology or trade or something about what the people were doing in the past.”
Often, though, the age of the material is really the question. After mass spec analysis, she sends the prepared samples for measurement of the 14C to another collaborator at the accelerator mass spectrometry facility at UC Irvine.
“Chemistry is just a piece of the full archeology. I’m not the person who goes and digs in the dirt – I tried that one summer it was really hard! When you think of archeology you think of Indiana Jones, not a person in a lab coat. But in the lab, there’s amazing stuff going on – such as using proteomics to figure out what people were eating based on the plaque stuck in their teeth.”
Armitage started down this fascinating path as an undergraduate at Thiel College in Pennsylvania, where she spent a summer in the field excavating a Woodland site and later as a graduate student at Texas A&M University working on radiocarbon dating rock paintings. Her first academic job was at St. Mary’s College of Maryland, where she worked with historic archeologists to study bricks and soil. Those former colleagues connected her later at EMU to the glue project with Ferry Farm. She collaborated with the Detroit Institute of Art on the African mask, then characterized organic colorants in ancient textiles at the Michael C. Carlos museum at Emory University. Many of these projects were supported with Faculty Research Fellowships from EMU. “We have tiny fragments of the textiles and looking at dyes as well as metals that help the dyes stick into the fibers better and give brighter colors. We’re working on binding media, organic pigments, and paintings. We’ve got plans to look at mummy resins and ceramic residues. There’s always something interesting coming in,” she says.
Such as the Peruvian beer mentioned earlier. “So many of these things have a weird story – I was with my students at Pittcon 2014 and met a very enthusiastic student who thought DART was super cool. He asked if he could come to Eastern and try running samples. One day, he showed up on a bus with box full of stuff – chocolate residues, beer residues - we ran everything (through the mass spec) in a day. I hadn’t paid close attention until about a year later one of my students said they’d heard about the work on “Science Friday” – the archeologists at Field Museum were on Science Friday and mentioned it.” Pieces of the ceramics used to store Peruvian beer a thousand years ago had been brought to her 3rd hand from the archeologists who were looking to see if beer made out of just corn or molle berries (also known as pink peppercorns, Schinus molle), or a relative of those. The story also showed up in National Geographic and Atlas Obscura.
“This spring we started looking at the content of what we thought were perfume bottles from the Greco-Roman period. We were able to go through and pick out most of the fatty acids, then do GC-MS sample prep. But first we can get more information without having to prepare all of them without a lengthy quantification and derivative process – we can get quick scan with DART. We found some really weird stuff – some started to break down and we got really strong signals that could come from copper. Some of it we ran on the SEM while at Pittcon and found lead in there. Right now, we’re using a Neoscope™ on loan from JEOL to look more at the elemental composition of the colorful residues.”
In archaeological chemistry, it’s important to keep in mind that we’re trying to learn about people: what materials and technologies they used, which might tell us about their status in society or when they created the painting or textile we’re studying. Our work in the lab is only part of the story, and why we work in collaboration with archaeologists and art historians to learn all we can about these precious materials.
In addition to all the archeological chemistry work she does, Armitage is very busy teaching several courses each semester and taking care of all the instrumentation in her lab. Others use the instruments as well, such as the biochemistry lab that analyzes their organic creations using Paper Spray™, for instance, to check peptides. While the analysis may be fast, it’s important to emphasize the science both in and out of the lab.