Distinguishing real from fake ivory products by elemental analyses: A Bayesian hybrid classification method

Kittisak Buddhachat; Janine L Brown; Chatchote Thitaram; Sarisa Klinhom; Korakot Nganvongpanit

doi:10.1016/j.forsciint.2017.01.016

Distinguishing real from fake ivory products by elemental analyses: A Bayesian hybrid classification method

Forensic Sci Int. 2017 Mar:272:142-149. doi: 10.1016/j.forsciint.2017.01.016. Epub 2017 Jan 21.

Authors

Kittisak Buddhachat¹, Janine L Brown², Chatchote Thitaram³, Sarisa Klinhom⁴, Korakot Nganvongpanit⁵

Affiliations

¹ Animal Bone and Joint Research Laboratory, Department of Veterinary Biosciences and Public Health, Faculty of Veterinary Medicine, Chiang Mai University, Chiang Mai 50100, Thailand; Department of Biology, Faculty of Science, Naresuan University, Phitsanulok 65000, Thailand. Electronic address: k_buddhachat@yahoo.com.
² Smithsonian Conservation Biology Institute, Center for Species Survival, 1500 Remount Road, Front Royal, VA 22630, USA. Electronic address: BrownJan@si.edu.
³ Center of Excellence in Elephant Research and Education, Faculty of Veterinary Medicine, Chiang Mai University, Chiang Mai 50100, Thailand. Electronic address: cthitaram@gmail.com.
⁴ Center of Excellence in Elephant Research and Education, Faculty of Veterinary Medicine, Chiang Mai University, Chiang Mai 50100, Thailand. Electronic address: yui.sarisarisa@gmail.com.
⁵ Animal Bone and Joint Research Laboratory, Department of Veterinary Biosciences and Public Health, Faculty of Veterinary Medicine, Chiang Mai University, Chiang Mai 50100, Thailand; Center of Excellence in Elephant Research and Education, Faculty of Veterinary Medicine, Chiang Mai University, Chiang Mai 50100, Thailand. Electronic address: korakot.n@cmu.ac.th.

PMID: 28157639
DOI: 10.1016/j.forsciint.2017.01.016

Abstract

As laws tighten to limit commercial ivory trading and protect threatened species like whales and elephants, increased sales of fake ivory products have become widespread. This study describes a method, handheld X-ray fluorescence (XRF) as a noninvasive technique for elemental analysis, to differentiate quickly between ivory (Asian and African elephant, mammoth) from non-ivory (bones, teeth, antler, horn, wood, synthetic resin, rock) materials. An equation consisting of 20 elements and light elements from a stepwise discriminant analysis was used to classify samples, followed by Bayesian binary regression to determine the probability of a sample being 'ivory', with complementary log log analysis to identify the best fit model for this purpose. This Bayesian hybrid classification model was 93% accurate with 92% precision in discriminating ivory from non-ivory materials. The method was then validated by scanning an additional ivory and non-ivory samples, correctly identifying bone as not ivory with >95% accuracy, except elephant bone, which was 72%. It was less accurate for wood and rock (25-85%); however, a preliminary screening to determine if samples are not Ca-dominant could eliminate inorganic materials. In conclusion, elemental analyses by XRF can be used to identify several forms of fake ivory samples, which could have forensic application.

Keywords: Bayesian; Bone; Classification; Elephant; Ivory.