title: Simultaneous analysis of aspartame and its hydrolysis products of Coca-Cola Zero by on-line postcolumn derivation fluorescence detection and ultraviolet detection coupled two-dimensional high-performance liquid chromatography.
abstract: An innovative two-dimensional high-performance liquid chromatography system was developed for the simultaneous analysis of aspartame and its hydrolysis products of Coca-Cola Zero. A C8 reversed-phase chromatographic column with ultraviolet detection was used as the first dimension for the determination of aspartame, and a ligand-exchange chromatographic column with on-line postcolumn derivation fluorescence detection was employed as the second dimension for the analysis of amino acid enantiomers. The fluorimetric derivative reagent of amino acid enantiomers was o-phthaldialdehyde. The hydrolysis of aspartame in Coca-Cola Zero was induced by electric-heating or microwave heating. Aspartame was quantified by the matrix matched external standard calibration curve with a linear concentration range of 0-50 μg mL(-1) (r(2)=0.9984). The limit of detection (LOD) and the limit of quantification (LOQ) were 1.3 μg mL(-1) and 4.3 μg mL(-1), respectively. The amino acid enantiomers was analyzed by the matrix matched internal standard calibration method (D-leucine as the internal standard) with a linear concentration range of 0-10 μg mL(-1) (r(2)=0.9988-0.9997). The LODs and LOQs for L- and D-aspartic acid and L- and D-phenylalanine were 0.16-0.17 μg mL(-1) and 0.52-0.55 μg mL(-1), respectively, that was 12-13 times more sensitive than ultraviolet detection. The overall analysis accuracy for aspartame and amino acid enantiomers was 90.2-99.2% and 90.4-96.2%, respectively. The overall analysis precision for aspartame and amino acid enantiomers was 0.1-1.7% and 0.5-6.7%, respectively. Generally, the extent of aspartame hydrolysis increases with the increase of electro-thermal temperature, microwave power, and the duration of hydrolysis time. D-aspartic acid and D-phenylalanine can be observed with the electro-thermal racemization at the hydrolysis temperature 120°C for 1 day and only D-aspartic acid can be observed at the hydrolysis temperature 90°C for 2 and 3 days. For the microwave induced hydrolysis, only L-aspartic acid was detected at the power 560 W for 1 min and 320 W for 3 min.
authors.affiliation: Department of Chemistry, Chung Yuan Christian University, Chungli, Taiwan, ROC. chengce@cycu.edu.tw
authors.forename: Cheanyeh
authors.initials: C
authors.lastname: Cheng
authors.forename: Shing-Chen
authors.initials: SC
authors.lastname: Wu
mesh_terms: D001218:Aspartame / Q000031:analogs & derivatives / Q000032:analysis* / Q000737:chemistry; D002253:Carbonated Beverages / Q000032:analysis*; D002851:Chromatography, High Pressure Liquid / Q000295:instrumentation / Q000379:methods*; D056148:Chromatography, Reverse-Phase; D006868:Hydrolysis; D016018:Least-Squares Analysis; D008872:Microwaves; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013050:Spectrometry, Fluorescence / Q000379:methods*; D013056:Spectrophotometry, Ultraviolet / Q000379:methods*; D013237:Stereoisomerism
chemical_list: D001218:Aspartame