In 1994, Chinese student Zhu Ling began to experience abdominal pain, hair loss and partial paralysis. By the time the doctors diagnosed Ling four months later with a lethal poison, she was in a coma. Ling survived, but she suffered prolonged neurological damage. The police investigation determined that Ling was deliberately poisoned, but the case has not yet been resolved.
Two decades after poisoning, Ling's family member asked Richard Ash, an associate researcher at the University of Maryland University of Geology, to analyze several Ling hairs collected in 1994 and 1995 to determine her poisoning schedule. Although gray specializes in geological sample analysis, he often assists various researchers in analyzing micronutrients in samples using mass spectrometry, which allows one to estimate elements in parts of a billion.
In October 2018 Ash published the results in a magazine International Forensic Science, for the first time discovering that the victim has long been exposed to many tallium juices.
"In my opinion, this is the first use of mass spectrometry to restore the period of a long-lasting case of intentional heavy metal poisoning," Ash said. "The analysis showed that the victim was poisoned at many doses, which over time increased in frequency and concentration."
Mass spectrometry makes it easy to find far-reaching aluminum hair, but it's difficult to measure the hair sample with thallium. Other laboratories turned to Min He, Ling's family partner and co-author of Ash's study, because there was no definite method for this type of analysis. "Mass spectrometry is not good at measuring concentrations," Ash said. "To do this, you need a standard reference material to compare your sample with.
And there are no standards that are suitable for measuring tallium concentration directly from the hair. "
The ash was made according to its standard using standard reference material made from ornamental leaves and developed by the National Institute of Standards and Technology (NIST) to identify certain elements in biological samples. Gray added a certain amount of talite to the NIST material to create a set of new standards that allowed him to determine how much tallium was for the injured hair.
As an additional level of quality control, Ash tested its measurements derived from standard NIST against the powdered hair standard from China and found that its measurement elements in the injured hair samples were closely related to those powdered hair standards.
"To be fair, I was surprised that the new standard worked so well," Ash said. "In developing its standard, it was shot dead in the dark, but it paid off."
Further, Ash was used to increase human hair, and chemicals from the body are included at constant speed. Due to this characteristic, determining the distribution of certain metals along the hair length is a definite method for determining the time and dose of a person subject to the metal.
To measure the tallium of the victim's hair, the peeling scanned the hair length with an ultraviolet laser. Laser energy converted the oldest hair layer into small particles. The ashes were then mass spectrometers for the analysis of tallium particles. Using hair growth rate and laser scanning speed, Pelens transformed his measurements of the timing of taking tallies.
Ash used this method to analyze several hairs of the victim, collected at different times in 1994 and 1995. Some hair that began to grow when Ling was asymptomatic revealed the effects of a sporadic stomach about four months, increasing the dose and frequency until hair was lost in December 1994. The second matt that fell around March 1995 showed a dose of about two weeks of prolonged high doses of tallium.
The ashes also revealed a high concentration of tala in the first hair, which corresponded to a short period when Ling suffered loss of vision but did not have symptoms of the gastrointestinal tract. As indicated in the study, this conclusion suggests that the victim was probably the first to be contagious with eye contact, but later – she was poisoned by oral swallowing.
In publishing his method and opinion, Pale hopes that his work in the future can help with the research of heavy metal poisoning and maybe even the decades old matter presented to him by this field of research.
"I hope that the new information provided by our work may at some point lead to the perpetrator being held accountable, and Zhu Ling's family regrets seeing it," Ash said.
A hair substance can be a marker for alcohol consumption
Richard David Ash et al. Details of poisoning cases with a solvent discovered by a separate analysis of the hair by laser ablation, inductively coupled plasma mass spectrometry, International Forensic Science (2018). DOI: 10.1016 / j.forsciint.2018.10.002