title: Determination of vitamin C and preservatives in beverages by conventional capillary electrophoresis and microchip electrophoresis with capacitively coupled contactless conductivity detection.
abstract: The separation and detection of commonly used preservatives (benzoate, sorbate) and vitamin C by both conventional CE and microchip electrophoresis with capacitively coupled contactless conductivity detection is presented. The separation was optimized by adjusting the pH-value of the buffer and the use of hydroxypropyl-beta-CD (HP-beta-CD) and CTAB as additives. For conventional CE, optimal separation conditions were achieved in a histidine/tartrate buffer at pH 6.5, containing 0.025% HP-beta-CD and 0.1 mM CTAB. LOD ranged from 0.5 to 3 mg/L (S/N = 3) and the RSDs for migration time and peak area were less than 0.1 and 2%, respectively. A considerable reduction of analysis time can be accomplished by using microchip electrophoresis without significant loss in sensitivity under optimal separation conditions. A histidine/tartrate buffer at pH 6.5, incorporating 0.06% HP-beta-CD and 0.25 mM CTAB, gave detection limits ranging between 3 and 10 mg/L and satisfactory reproducibilities of < or =0.4% for the migration time and < or =3.5% for the peak area. The methods developed are useful for the quantitative determination of food additives in real samples such as soft drinks and vitamin C tablets.
authors.affiliation: Department of Chemistry, National University of Singapore, Republic of Singapore.
authors.forename: Wai Siang
authors.initials: WS
authors.lastname: Law
authors.forename: Pavel
authors.initials: P
authors.lastname: Kubán
authors.forename: Jian Hong
authors.initials: JH
authors.lastname: Zhao
authors.forename: Sam Fong Yau
authors.initials: SF
authors.lastname: Li
authors.forename: Peter C
authors.initials: PC
authors.lastname: Hauser
mesh_terms: D000073738:2-Hydroxypropyl-beta-cyclodextrin; D000085:Acetates / Q000032:analysis; D001205:Ascorbic Acid / Q000032:analysis*; D001565:Benzoates / Q000032:analysis; D001628:Beverages / Q000032:analysis*; D000077286:Cetrimonium; D002593:Cetrimonium Compounds / Q000737:chemistry; D004553:Electric Conductivity; D019075:Electrophoresis, Capillary / Q000379:methods*; D046209:Electrophoresis, Microchip / Q000379:methods*; D005503:Food Additives / Q000032:analysis; D005520:Food Preservatives / Q000032:analysis*; D006863:Hydrogen-Ion Concentration; D019344:Lactic Acid / Q000032:analysis; D013011:Sorbic Acid / Q000032:analysis; D047392:beta-Cyclodextrins / Q000737:chemistry
chemical_list: D000085:Acetates; D001565:Benzoates; D002593:Cetrimonium Compounds; D005503:Food Additives; D005520:Food Preservatives; D047392:beta-Cyclodextrins; D000073738:2-Hydroxypropyl-beta-cyclodextrin; D019344:Lactic Acid; D001205:Ascorbic Acid; D013011:Sorbic Acid; D000077286:Cetrimonium