A Comparison of a Novel Muffle Furnace-based Alkaline Fusion Digestion Technique with Hydrofluoric Acid Microwave and Bunsen Burner Alkaline Fusion Digestion Techniques for Analysis of Anthropogenic Titanium Dioxide in Environmental Matrices

R.G. Silva, M.N. Nadagouda, J. Webster, S. Govindaswamy, K.D. Hristovski, R.G. Ford, C. Patterson, C.A. Impellitteri
Shaw Environmental Inc., US

Keywords: titanium dioxide, nanoparticles, muffle furnace, alkaline fusion

Summary:

A novel muffle furnace (MF)-based potassium hydroxide (KOH) fusion digestion technique was developed and its comparative digestion and dissolution efficacy for different titanium dioxide nanoparticles (TiO2-NPs)/environmental matrices was evaluated. Statistical analysis of results revealed that the dissolution of TiO2-NP spiked environmental matrices in the MF-based KOH fusion was comparable to the BB-based KOH fusion. For pure TiO2 particles, the measured Ti recoveries compared to calculated values were 96%, 85% and 87% for anatase, brookite and rutile TiO2-NPs, respectively, by the MF-based fusion technique. These recoveries were consistent and less variable than the BB-based fusion technique recoveries of 104%, 97% and 72% and MW-based HNO3/HF mixed acids digestion recoveries of 80%, 81% and 14%, respectively, for anatase, brookite and rutile TiO2-NPs. Additionally, the drop in recovery eficiencies and precision can be counteracted by more thorough homogenization of the spiked mixtures and by increasing the mass of KOH in the MF fusion process from 1.6 g to 10.0 g. Thus, the MF-based fusion technique can be used to dissolve a large number of samples in a shorter time (e.g., 500 samples/8 hours) while conserving energy and eliminating health and safety risks from methods involving HF.