A comparative evaluation of analytical methods for the detection of titanium dioxide in chewing gum

The EU ban on the use of titanium dioxide (TiO₂) as a food additive (E 171) has highlighted the need for harmonised and robust analytical methods to ensure uniform regulatory compliance and safeguard consumer health. This study compares three instrumental methods, namely portable X-ray fluorescence (pXRF), macro-Raman spectroscopy (applied to both intact and digested samples), and inductively coupled plasma mass spectrometry (ICP-MS), for detecting and quantifying titanium (Ti) or titanium dioxide (TiO₂) in 35 chewing-gum samples of different shapes and colours, outlining their specific advantages and limitations. The results show that two items contained E 171, in agreement with the label declarations, and demonstrate, for the specific case of chewing gums where TiO₂ is added to the coating, high concordance among the four applied analytical approaches. pXRF and Macro-Raman spectroscopy, when applied to intact samples, enable safe and rapid screening on the presence of Ti and TiO₂ respectively in the sample's surface while a mild acidic digestion step followed by Raman analysis provides a confirmatory step for complex or interfered spectra. ICP-MS, despite relying on careful and laborious sample preparation, allows accurate quantitative results of Ti to estimate TiO₂. Thanks to its sensitivity and elemental specificity, low Ti levels can be determined which however may not necessarily indicate intentional E 171 addition.