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Dirk-Henning Menz, Nicolas Feltgen, Thorsten Lechner, Helge Menz, Bernd-Kristof Müller, Joachim Dresp, Hans Hoerauf; Hydrofluoric Acid and Other Impurities in Toxic Perfluorooctane Batches. Trans. Vis. Sci. Tech. 2019;8(3):24. doi: 10.1167/tvst.8.3.24.
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© ARVO (1962-2015); The Authors (2016-present)
The complications with cytotoxic perfluorooctane (PFO) batches reported in 2015 were attributed to reactive underfluorinated impurities whose chemical identity and behavior still need to be clarified.
Material and Methods:
We analyzed original packaged samples of Ala®octa batches involved in several reported cases of retinal toxicity. (A) The impurity profile was determined. (B) pH and fluoride ion content were measured. (C) Extraction with olive oil was performed to investigate differences in lipophilia among perfluorinated liquid (PFCL) as a measure for penetration of lipophilic cell membranes followed by measurements (A) and (B).
(A) The detected impurities can be divided into: (1) reactive underfluorinated compounds and their degradation products including hydrogen fluoride (HF), (2) nonreactive underfluorinated compounds, (3) surface active compounds, (4) nonreactive fluorinated compounds, and (5) leachables from primary packaging components. The highest acute toxic potential is associated with the impurities of group (1). (B) HF was detected as a degradation product of reactive underfluorinated impurities by relying on the pH values and fluoride ion content of the water extracts. (C) Lipophilic impurities dissolved in PFO migrate into lipophilic extraction medium. In particular, HF is rapidly transferred in this way.
HF as degradation product of unstable or reactive underfluorinated contaminants seems of particular importance triggering the acute toxicity of affected PFO. Contamination related toxicity and unwanted side effects can only be reliably excluded via analytical controlled multistage, high-purification processes.
In Ala®octa batches different impurities show retinal toxicity. HF seems of particular importance of the acute toxicity of PFO.
Equation 1: Reaction scheme of the general reaction of underfluorinated impurities with strong bases (RF = fully fluorinated substituent; Nu = nucleophiles that promote fluoride-cleavage under strong and harsh basic conditions; F− = fluoride ions).
Equation 2: Reaction scheme of spontaneous conversion of unstable reactive underfluorinated impurities.
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