title: Reichardt's dye and its reactions with the alkylating agents 4-chloro-1-butanol, ethyl methanesulfonate, 1-bromobutane and Fast Red B - a potentially useful reagent for the detection of genotoxic impurities in pharmaceuticals.
abstract: OBJECTIVE
  Alkylating agents are potentially genotoxic impurities that may be present in drug products. These impurities occur in pharmaceuticals as by-products from the synthetic steps involved in drug production, as impurities in starting materials or from in-situ reactions that take place in the final drug product. Currently, analysis for genotoxic impurities is typically carried out using either HPLC/MS or GC/MS. These techniques require specialist expertise, have long analysis times and often use sample clean-up procedures. Reichardt's dye is well known for its solvatochromic properties. In this paper the dye's ability to undergo alkylation is reported.
  
  
  METHODS
  The reaction between Reichardt's dye and alkylating agents such as 4-chloro-1-butanol and ethyl methanesulfonate was monitored spectrophotometrically at 618 nm in acetonitrile and 624 nm in N,N-dimethylformamide.
  
  
  RESULTS
  Changes in absorption were observed using low levels of alkylating agent (5-10 parts per million). Alkylation of the dye with 4-chloro-1-butanol and ethyl methanesulfonate was confirmed. Reichardt's dye, and its changing UV absorption, was examined in the presence of paracetamol (10 and 100 mg/ml). Whilst the alkylation-induced changes in UV absorption were not as pronounced as with standard solutions, detection of alkylation was still possible.
  
  
  CONCLUSIONS
  Using standard solutions and in the presence of a drug matrix, Reichardt's dye shows promise as a reagent for detection of low levels of industrially important alkylating agents.
authors.affiliation: Cranfield Health, Cranfield University, UK. d.k.corrigan.s04@cranfield.ac.uk
authors.forename: Damion K
authors.initials: DK
authors.lastname: Corrigan
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Whitcombe
authors.forename: Sean
authors.initials: S
authors.lastname: McCrossen
authors.forename: Sergey
authors.initials: S
authors.lastname: Piletsky
mesh_terms: D000477:Alkylating Agents / Q000032:analysis*; D002626:Chemistry, Pharmaceutical; D002724:Chlorobutanol / Q000031:analogs & derivatives / Q000032:analysis; D002863:Chromogenic Compounds / Q000737:chemistry; D003979:Diazonium Compounds / Q000032:analysis; D004340:Drug Contamination; D005020:Ethyl Methanesulfonate / Q000032:analysis; D006842:Hydrocarbons, Brominated / Q000032:analysis; D066298:In Vitro Techniques; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D009153:Mutagens / Q000032:analysis*; D011726:Pyridinium Compounds / Q000737:chemistry*
chemical_list: C541029:2,6-diphenyl-4-(2,4,6-triphenyl-1-pyridinio)phenolate; D000477:Alkylating Agents; D002863:Chromogenic Compounds; D003979:Diazonium Compounds; C541030:Fast Red B; D006842:Hydrocarbons, Brominated; D009153:Mutagens; D011726:Pyridinium Compounds; C525905:4-chloro-1-butanol; D005020:Ethyl Methanesulfonate; D002724:Chlorobutanol; C047757:butyl bromide