Beasley, Bartelink, Taylor, and Miller, 2014, Comparison of transmission FTIR, ATR, and DRIFT spectra: implications for assessment of bone bioapatite diagenesis: Journal of ARchaeological Science, v. 46, p. 16-22.
What’s it about?
One of the challenges of studying the chemistry of fossil bones and teeth is being confident that the chemistry of the fossils is unaltered from its original state (that is, the bones and teeth still faithfully record the chemistry of the living animal they came from). During the process of fossilization, the mineral and chemical structure of bones and teeth are altered from what they were in life, a process called diagenesis.
Fourier Transform Infrared (FTIR) spectroscopy is one way to measure the extent of diagenesis in bones. However, there are three different ways to use FTIR on bones, transmission FTIR, ATR, and DRIFT. This paper compares all three methods using a large sample set of fossil and modern bones.
Why does it matter?
It’s important to know how badly altered the chemistry of a fossil may have been altered from its original state. It’s equally important to use the most practical and accurate means to do so. All three FTIR methods have advantages and disadvantages.
Why did I read this?
I have attempted to use ATR methods to assess diagenesis in tooth enamel before, forgoing transmission FTIR and DRIFT because they are more involved processes and require larger samples. I wanted to verify if my choice was a good one.
What did I learn?
Turns out that all three methods yield different results for the same samples (and are therefore not cross-comparable), but that ATR does appear to do the best job of distinguishing modern from fossil bone samples. Therefore, using ATR preferentially may be the best option.