- Simultaneous determination of paracetamol, chlorzoxazone, and related impurities 4-aminophenol, 4'-chloroacetanilide, and p-chlorophenol in pharmaceutical preparations by high-performance liquid chromatography. Ali, M.S., Rafiuddin, S., Ghori, M., Kahtri, A.R. Journal of AOAC International (2007)