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Examining the efficiency of muffle furnance-induced alkaline hydrolysis in determining the titanium content of environmental samples containing engineered titanium dioxide particles
Silva, G., M. Nadagouda, J. Webster, S. Govindaswamy, K. Hristovski, R. Ford, C. Patterson, AND C. Impellitteri. Examining the efficiency of muffle furnance-induced alkaline hydrolysis in determining the titanium content of environmental samples containing engineered titanium dioxide particles. Environmental Science: Processes & Impacts. RSC Publishing, Cambridge, Uk, 15(3):645-652, (2013).
This work provides researchers with a less costly safer method for quantifying titanium in samples containing titanium nanoparticles.
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. Digestion of different environmental samples containing sediments, clay minerals and humic acid with and without TiO2-NPs was first performed utilizing the MF-based KOH fusion technique and its dissolution efficacy was compared to a Bunsen burner (BB)-based KOH fusion method. The three types of TiO2-NPs were then digested with aforementioned KOH fusion techniques and microwave (MW)-based nitric (HNO3)/hydrofluoric (HF) mixed acid digestion methods. 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. 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 MV-based HNO3/HF mixed acids digestion recoveries of 80%, 81% and 14%, respectively, for anatase, brookite and rutile TiO2-NPs. The MF-based fusion technique is consistently superior in digestion efficiency across all three TiO2-NPs and complete dissolution of the refractory metal titanium (Ti) can be achieved in a simpler experimental set-up. The MF-based fusion technique required 20 minutes for digestion of 25 samples (based on in-house Lindberg MF capacity) compared to 8 hours for the same number of samples using the BB-based fusion technique. 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.