Greatest Hits 4 – Getting Technical: Stable Isotope Analysis, Part 1

Chris Knowles, Assistant Professor at the Oregon Wood Innovation Center of Oregon State University and I were chatting about the feasibility of using new technologies in determining the legality of wood the other day and he tried to explain some of the actual science behind it to me. Now he’s going to try to explain it to everyone here!  I’m going to break this out into two parts not to overwhelm everyone.

So, Chris, why should we slog through this science?

Claims have been made that we have a variety of scientific techniques that can now be used to determine, with some degree of accuracy, the geographic origin of wood products. The question is if they are feasible and practical for extensive real world applications. I’d say they have some potential, but it’s going to take a lot of time and data collection before it will really be a meaningful tool for determining legality.

So are we talking DNA testing?

That’s one option, most folks understand that. DNA testing for wood, at least conceptually, is similar to what everyone thinks of from TV shows and movies—trying to identify the inherent genetic makeup of the tree. Let’s just say that we are not nearly as advanced with DNA testing for wood as TV would lead you to believe.

However there’s another technique often paired with that which I think people need to understand. That’s “stable isotope analysis.”

Can I call that SIA for short?

Well, I have seen it referred to that in some publications although unfortunately, I don’t think “SIA” is a common acronym yet. That said, if the technology usage spreads, it might become one.

What’s the difference in use?

The DNA testing method is often slightly more focused—claims have been made that you can ID trees within a 50 mile radius. I would assume that DNA drift would start to occur over distance, so this is possible. The stable isotope analysis tends to cover a wider area of investigation. Definitely it could identify region of origin—tell the difference between American, European and Chinese Oaks for example.

OK, so what is stable isotope analysis?

Before we can discuss stable isotope analysis we must review some basic chemistry.

Oh joy!  OK, go ahead.

First let’s define an isotope. Recall that an element is made up of several components, including protons and neutrons. Isotopes are variations of an element such that each variant contains the same number of protons (the atomic number from the periodic table) but contains different number so neutrons.

Take the element Carbon as an example. Carbon is an element that is often used in stable isotope analysis. Carbon, which has 6 protons and therefore an atomic number of 6, has three isotopes – carbon-12, carbon-13, and carbon-14. Each of these variations of carbon have 6 protons but where they differ is in the number of neutrons that they contain. Carbon-12 has 6 neutrons, carbon-13 has 7 neutrons and carbon-14 has 8 neutrons. These different isotopes of carbon occur naturally and vary in their concentrations based on geography.

Some of the isotopes of a given element are stable while others are radioactive. The stable isotopes tend to maintain their composition over time while the radioactive isotopes tend to degrade over time. Using Carbon as the example again, carbon-12 and carbon-13 are considered stable isotopes while carbon-14 is the radioactive form.

Got you. Is this like Carbon Dating?  And I mean time dating, not out for dinner dating, of course…

That’s one use. Stable isotope analysis is a tool that allows for analyzing the ratio of stable isotopes to radioactive isotopes of a given element in a material. This information can then be used for several purposes including dating a material (commonly referred to as carbon dating) or, in our case, tracking the location a material was grown in.

Oxygen, carbon, nitrogen, hydrogen, and sulfur are the elements that are most commonly utilized for stable isotope analysis. These elements vary in natural systems based on factors such as distance from the ocean, distance from the poles, temperature, and rainfall. Recent advances in measurement technology have expanded the number of elements to include elements such as iron, copper, zinc, and molybdenum. These elements are essential micronutrients for trees and vary in the concentrations within the soil.

OK, we all need a break to absorb that!  We’ll figure out how the wood industry can USE this science next week.

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