Researchers at Penn State Univ. have used solid phase microextraction (SPME) to profile the chemicals released by decomposing bodies. In an advance toward the first portable device for detecting human bodies buried in disasters and at crime scenes, the scientists have reported their early results to establish the chemical fingerprint of death at the recent National Meeting of the American Chemical Society.
PSU researchers Dan Sykes and Sarah Jones said that a chemical profile of decomposition could eventually lead to a portable device for detecting human bodies at crime scenes and disaster areas.
Today, cadaver dogs are the gold standard for detecting and recovering bodies in earthquakes, tornadoes, hurricanes, and other natural disasters. "These dogs are highly effective, but it takes lots of time, expense and manpower to train them. If there was a device that was as effective for a fraction of the cost, that would be something worth pursuing," says Sykes.
A euthanized pig is placed in an odor collecting unit with special fibers that capture the gases arising off the carcass. |
To develop a sensing device, scientists must identify what gases are released as bodies decompose under a variety of natural environmental conditions, Jones noted. In addition, they must detail the time sequence in which those odorant chemicals are released in the hours and days after death. "What we're looking for is the profile of what gases are released when we die, as well as how the environment and the manner in which we die affects this profile," Jones says.Decomposing bodies release more than 30 compounds. Some, like the aptly-named "putrescine" and "cadaverine," develop early in the decomposition process. Past studies used donated human bodies that were two to three days old. As a result, these studies were unable to detect putrescine, cadaverine, and other compounds that appear very early in the decomposition process. Jones and Sykes side-stepped that problem by using pigs euthanized under humane conditions to study decomposition immediately after death.
"Pigs are good models for this research," says Jones. "They go through the same phases of decomposition as humans, as well as the same number of stages. And those stages last about as long in pigs as they do in humans before complete decomposition occurs and only the bones remain."
Sykes and Jones placed dead pigs in specially designed odor-collecting units under a variety of environmental conditions. Above each specimen, they affixed special sensors known as solid phase micro extraction (SPME) fibers to capture the gases. These specially-coated fibers are widely used to sample chemical composition of air. Jones and Sykes collected odor data every 6 to 12 hours over the course of a week.
Studying the week's worth of odor data, a clear chemical profile emerged. "In days one through three, we found precursors to indole, which is a really good sign. On day three, we found indole and putrescine, the main compounds that we were trying to detect," Jones says. They now are capturing gases released in a variety of other scenarios to re-construct the different ways human bodies could decompose, creating a more complete picture of decomposition.
Source: Penn State Univ.