Exploration of the techniques and applications of δ2H, δ18O and δ13C stable isotope analysis for the authentication of raw cotton
As the practices of fraud and use of child labour in the cotton industry become more sophisticated and harder to prevent, undermining detection using falsified documentation becomes easy to achieve. Stable isotopes are frequently used in analytical forensics as a means of authenticating raw cotton by utilizing the stable isotope ratio determinations of light elements H, O, C, N and S. The use of stable isotope in analytical forensics tend to complement the conventional chemical methods of analysis which are not as able to determine the regional provenance of cotton explicitly. The δ2H and δ18O isotopic values of precipitation vary across the globe. This variation provides a unique fingerprint for different parts of the world. The δ13C incorporated through the water taken up by the plant via roots and the process of photosynthesis in the cotton plant is reflected in the cellulose fibre. Hence, these isotopic ratios are potentially ideal means of determining the origin of the raw cotton samples. This work presents, for the first time, the effects of manufacturing processing techniques on the 2H and 18O isotopic values of cotton through the analysis of 2H and 18O isotopic abundance of the processed cotton fibres on High-Temperature Conversion-Isotope Ratio Mass Spectrometry (TC/EA-IRMS). Exploration of environmental drivers that can contribute to the variations in the stable isotope ratios and reasons for regional differences in stable isotope ratios of cotton are also discussed in this dissertation. These effects are assessed to determine any potential alteration to the manufacturing processes of cotton and to confirm a robust statistical measure of the natural range and variance of stable isotopic ratios of cotton in different parts of the world respectively. Hence, employing multivariate statistics as a means of demonstrating and modeling the correlation between the variations and geographical regions from where the cotton samples originate. The results are presented for raw cotton from 22 countries around the world and processed cotton from the USA. The results for the raw cotton study deduced that there is a significant difference in raw cotton from different countries around the world. Moreover, the second part of the study which was done with the processed cotton proved that cotton could be traced back to its origin even after it has undergone different processing techniques. The results demonstrate the potential for an underlying presumption of results for δ2H, δ18O and δ13C isotopic values of cotton.
Advisor: Frew, Russell; McComb, Kiri
Degree Name: Master of Science
Degree Discipline: Chemistry
Publisher: University of Otago
Keywords: Stable Isotopes Ratios, Analytical Forensics, Authenticating, Precipitation, δ2H, δ18O, Photosynthesis, δ13C, Raw Cotton, Manufacturing Processing Effects, Processed Cotton
Research Type: Thesis