Confirmation of ofloxacin precipitation in corneal deposits by microbore liquid chromatography-quadrupole time-of-flight tandem mass spectrometry.

We investigated the corneal precipitate of a 6-year-old boy with vernal keratoconjunctivitis (VKC), treated with topical ofloxacin 0.3% eyedrops. Because of the extremely small sample amount (corneal scraping), a very sensitive and specific method was needed with the possibility of an unambiguous identification of ofloxacin, supposed to be present in the precipitate. In this respect, tandem Q-TOF mass spectrometry combined with micro LC (1 mm I.D.) was chosen. Confirmation of the presence of ofloxacin in the deposit was obtained by means of the characteristic product ion spectrum produced by CID. This clearly indicated that the precipitate, removed by corneal scraping from the 6-year-old boy with VKC, contained ofloxacin.