title: Bromate peak distortion in ion chromatography in samples containing high chloride concentrations.
abstract: In this study, the effect of column overload of the matrix ion, chloride, on the elution peak profiles of trace bromate is investigated. The resultant peak profiles of chloride and bromate are explained on the basis of competitive Langmuir isotherms. The Thermo IonPac AS9-HC, AS19 and AS23 columns are recommended by the manufacturer for bromate (a carcinogen) analysis. Under trace conditions, these columns provide baseline resolution of bromate from matrix ions such as chloride (Rs=2.9, 3.3 and 3.2, respectively for the three columns). Injection of 10-300 mM chloride with both hydroxide and carbonate eluents resulted in overload on these columns. On the basis of competitive Langmuir isotherms, a deficiency in the local concentration of the more retained eluent in addition to analyte overload leads to fronting of the overloaded analyte peak. The peak asymmetries (B/A10%) for chloride changed from 1.0 (Gaussian) under trace conditions to 0.7 (fronting) at 300 mM Cl(-) for IonPac AS9-HC, 0.9-0.6 for AS19 and 0.8-0.5, for AS23, respectively. The 10mM bromate peak is initially near Gaussian (B/A10%=0.9) but becomes increasingly distorted and pulled back into the chloride peak as the concentration of chloride increased. Increasing the eluent strength reduced the pull-back effect on bromate and fronting in chloride in all cases.
authors.affiliation: Department of Chemistry, University of Alberta, Gunning/Lemieux Chemistry Centre, Edmonton, Alberta AB T6G 2G2, Canada.
authors.forename: Michael K
authors.initials: MK
authors.lastname: Pappoe
authors.affiliation: Department of Chemistry, University of Alberta, Gunning/Lemieux Chemistry Centre, Edmonton, Alberta AB T6G 2G2, Canada.
authors.forename: Mohammad Hosein
authors.initials: MH
authors.lastname: Naeeni
authors.affiliation: Department of Chemistry, University of Alberta, Gunning/Lemieux Chemistry Centre, Edmonton, Alberta AB T6G 2G2, Canada. Electronic address: charles.lucy@ualberta.ca.
authors.forename: Charles A
authors.initials: CA
authors.lastname: Lucy
mesh_terms: D001959:Bromates / Q000737:chemistry*; D002712:Chlorides / Q000737:chemistry*; D002852:Chromatography, Ion Exchange / Q000592:standards*
chemical_list: D001959:Bromates; D002712:Chlorides
keywords: Alkanol quaternary ammonium; Alkyl quaternary ammonium; Column overload; Eluent suppression; Langmuir competitive isotherms; Peak distortion; pull-back effect