Inorganic analysis of falsified medical products using X-ray fluorescence spectroscopy and chemometrics

Falsified medical products are increasingly prevalent on markets, threatening the health of patients. This study describes the benefits of Energy Dispersive X-Ray Fluorescence (ED-XRF) spectroscopy and chemometrics thus highlighting the importance of conducting inorganic analyses on falsified products. The XRF spectrum is a fingerprint containing the contribution of all chemical substances included in a suspect sample's formulation. Multivariate analysis of XRF spectra, using a properly validated classification model, allows for the authentication of suspect samples. The method is rapid, relying on multi-elemental measurements and involving minimal sample preparation. This methodology provided valuable information about samples inorganic composition and enabled the detection of falsifications of several sample types, including medicine, food supplement and cosmetic samples. Five suspect samples of Plavix® were investigated, and their XRF spectra were studied using chemometrics (Principal Component Analysis and Soft Independent Modelling of Class Analogies). A classification model was validated with positive and negative samples, and four suspect samples were identified as being falsified, whilst the fifth was concluded as an authentic medicine. ED-XRF spectroscopy was also applied on another medicine, a food supplement and three cosmetic samples, and high level of zinc was detected in the second sample and mercury was identified in the last. Estimation of the zinc content was possible using the fundamental parameters method. ED-XRF spectroscopy allows the analyst to conclude on the falsification of the samples and then to assess the harm to patient health.