title: Structural elucidation of main ozonation products of the artificial sweeteners cyclamate and acesulfame.
abstract: OBJECTIVE
  The two artificial sweeteners cyclamate (CYC) and acesulfame (ACE) have been detected in wastewater and drinking water treatment plants. As in both facilities ozonation might be applied, it is important to find out if undesired oxidation products (OPs) are formed.
  
  
  METHODS
  For the separation and detection of the OPs, several analytical techniques, including nuclear magnetic resonance experiments, were applied. In order to distinguish between direct ozone reaction and a radical mechanism, experiments were carried out at different pH values with and without scavenging OH radicals. Kinetic experiments were used for confirmation that the OPs are formed during short ozone contact time applied in waterworks. Samples from a waterworks using bank filtrate as raw water were analyzed in order to prove that the identified OPs are formed in real and full-scale ozone applications.
  
  
  RESULTS
  In the case of CYC, oxidation mainly occurs at the carbon atom, where the sulfonamide moiety is bound to the cyclohexyl ring. Consequently, amidosulfonic acid and cyclohexanone are formed as main OPs of CYC. When ozone reacts at another carbon atom of the ring a keto moiety is introduced into the CYC molecule. Acetic acid and the product ACE OP170, an anionic compound with m/z=170 and an aldehyde hydrate moiety, were identified as the main OPs for ACE. The observed reaction products suggest an ozone reaction according to the Criegee mechanism due to the presence of a C=C double bond. ACE OP170 was also detected after the ozonation unit of a full-scale drinking water treatment plant which uses surface water-influenced bank filtrate as raw water.
  
  
  CONCLUSIONS
  Acesulfame can be expected to be found in anthropogenic-influenced raw water used for drinking water production. However, when ACE OP170 is formed during ozonation, it is not expected to cause any problem for drinking water suppliers, because the primary findings suggest its removal in subsequent treatment steps, such as activated carbon filters.
authors.affiliation: Analytical Department, Water Technology Center Karlsruhe (TZW), Karlsruher Str. 84, 76139 Karlsruhe, Germany.
authors.forename: Marco
authors.initials: M
authors.lastname: Scheurer
authors.forename: Markus
authors.initials: M
authors.lastname: Godejohann
authors.forename: Arne
authors.initials: A
authors.lastname: Wick
authors.forename: Oliver
authors.initials: O
authors.lastname: Happel
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Ternes
authors.forename: Heinz-Jürgen
authors.initials: HJ
authors.lastname: Brauch
authors.forename: Wolfgang K L
authors.initials: WK
authors.lastname: Ruck
authors.forename: Frank Thomas
authors.initials: FT
authors.lastname: Lange
mesh_terms: D002606:Charcoal / Q000737:chemistry; D002845:Chromatography; D003494:Cyclamates / Q000737:chemistry*; D060766:Drinking Water / Q000737:chemistry; D005374:Filtration; D013058:Mass Spectrometry; D010084:Oxidation-Reduction; D010126:Ozone / Q000737:chemistry*; D013549:Sweetening Agents / Q000737:chemistry*; D013843:Thiazines / Q000737:chemistry*; D018508:Water Purification
chemical_list: D003494:Cyclamates; D060766:Drinking Water; D013549:Sweetening Agents; D013843:Thiazines; D002606:Charcoal; D010126:Ozone; C006362:acetosulfame