title: Detection of para-chloroaniline, reactive oxygen species, and 1-chloro-4-nitrobenzene in high concentrations of chlorhexidine and in a mixture of chlorhexidine and calcium hydroxide.
abstract: BACKGROUND
  Chlorhexidine (CHX) is likely to decompose into reactive by-products. This study evaluated the generation of 4-chloroaniline (pCA), reactive oxygen species (ROS), and 1-chloro-4-nitrobenzene in high concentrations of CHX and in a mixture of CHX and calcium hydroxide at different time points.
  
  
  METHODS
  A gas chromatography method was developed to detect pCA and CHX by-products. Mass spectroscopy was used to elucidate the structure of compounds. The samples, which were kept at 36.5°C and 95% relative humidity during the study, were analyzed immediately and 7 days after preparation.
  
  
  RESULTS
  pCA was detected in the 2% CHX solution and in the mixture of CHX and calcium hydroxide at all time points. pCA concentrations increased after storing under those conditions. The 2% CHX solution alone and the mixture of CHX and calcium hydroxide released ROS at all time points, but 1-chloro-4-nitrobenzene was not found.
  
  
  CONCLUSIONS
  pCA and ROS were identified as by-products of the 2% CHX aqueous solution alone and as ointment base of calcium hydroxide paste.
authors.affiliation: Department of Semiology and Clinics, Dental School, Federal University of Pelotas, Pelotas, Rio Grande do Sul, Brazil.
authors.forename: Luiz Eduardo
authors.initials: LE
authors.lastname: Barbin
authors.forename: Carlos
authors.initials: C
authors.lastname: Estrela
authors.forename: Débora Fernandes Costa
authors.initials: DF
authors.lastname: Guedes
authors.forename: Júlio César Emboava
authors.initials: JC
authors.lastname: Spanó
authors.forename: Manoel Damião
authors.initials: MD
authors.lastname: Sousa-Neto
authors.forename: Jesus Djalma
authors.initials: JD
authors.lastname: Pécora
mesh_terms: D000814:Aniline Compounds / Q000032:analysis*; D000891:Anti-Infective Agents, Local / Q000032:analysis / Q000737:chemistry*; D002126:Calcium Hydroxide / Q000032:analysis / Q000737:chemistry*; D002710:Chlorhexidine / Q000031:analogs & derivatives* / Q000032:analysis / Q000737:chemistry; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D006813:Humidity; D008422:Materials Testing; D009578:Nitrobenzenes / Q000032:analysis*; D017382:Reactive Oxygen Species / Q000032:analysis*; D013696:Temperature; D013997:Time Factors; D014365:Tryptophan Hydroxylase / Q000037:antagonists & inhibitors*
chemical_list: D000814:Aniline Compounds; D000891:Anti-Infective Agents, Local; D009578:Nitrobenzenes; D017382:Reactive Oxygen Species; C010407:4-chloronitrobenzene; D014365:Tryptophan Hydroxylase; C010882:chlorhexidine gluconate; D002126:Calcium Hydroxide; D002710:Chlorhexidine; C004658:4-chloroaniline