Interactions of perfluorocarbon liquids and silicone oil as characterized by mass spectrometry.

Perfluorocarbon liquids (PFCL) are used extensively in complex vitreoretinal surgery, sometimes before the placement of silicone oil (SiO). We suspected that PFCL and SiO interact physically when in opposition, potentially making their removal more difficult. The nature of some of these interactions was explored using a mass spectrometric approach in in-vitro and in-vivo samples. We incubated silicone oil (1,000 or 5,000 centistokes viscosity) and PFCL [perfluoro-n-octane (PFO) or perfluorotributylamine] together in vitro for 6 months and performed electron impact ionization mass spectrometry (EIMS) on the PFCL to characterize interactions between the liquid phases. Packaged samples of PFCL served as controls. We also examined in vivo samples of PFO which had been retained in human eyes for several months prior to surgical removal. Perfluorocarbon liquids packaged for surgical use all contain SiO in trace amounts, possibly as a manifestation of the processes used in their manufacture. Furthermore, all PFCLs incubated with SiO showed much more prominent contamination with SiO molecular fragments. PFCL was found in the SiO phase of eyes in which both liquids were present for extended periods of time. The EIMS analysis of in vivo samples suggested that proteins coat PFCL droplets, forming micelle-like structures. Medical-grade PFCLs contain small amounts of SiO, and PFCLs dissolve small amounts of oil into solution over time. Interactions between retained vitreous substitutes may have clinical relevance.