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

Introduction: 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 degrees 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.