Department of Chemistry, Chung Yuan Christian University, Chungli, Taiwan, ROC.
J Chromatogr A. 2011 May 20;1218(20):2976-83. doi: 10.1016/j.chroma.2011.03.033. Epub 2011 Apr 8.
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.
建立了一种用于同时分析可口可乐零的阿斯巴甜及其水解产物的二维高效液相色谱系统。采用 C8 反相色谱柱和紫外检测作为第一维，用于测定阿斯巴甜，采用配体交换色谱柱和在线柱后衍生荧光检测作为第二维，用于分析氨基酸对映体。氨基酸对映体的荧光衍生试剂为邻苯二醛。通过电加热或微波加热诱导可口可乐零中的阿斯巴甜水解。阿斯巴甜通过基质匹配外标校准曲线定量，线性浓度范围为 0-50 μg mL(-1)（r(2)=0.9984）。检测限（LOD）和定量限（LOQ）分别为 1.3 μg mL(-1)和 4.3 μg mL(-1)。氨基酸对映体通过基质匹配内标校准法（D-亮氨酸作为内标）分析，线性浓度范围为 0-10 μg mL(-1)（r(2)=0.9988-0.9997）。L-和 D-天冬氨酸以及 L-和 D-苯丙氨酸的 LODs 和 LOQs 分别为 0.16-0.17 μg mL(-1)和 0.52-0.55 μg mL(-1)，比紫外检测灵敏 12-13 倍。阿斯巴甜和氨基酸对映体的整体分析准确度分别为 90.2-99.2%和 90.4-96.2%。阿斯巴甜和氨基酸对映体的整体分析精密度分别为 0.1-1.7%和 0.5-6.7%。通常，随着电热温度、微波功率和水解时间的增加，阿斯巴甜的水解程度增加。在 120°C 水解温度下，电热消旋化 1 天可以观察到 D-天冬氨酸和 D-苯丙氨酸，而在 90°C 水解温度下 2 天和 3 天只能观察到 D-天冬氨酸。对于微波诱导水解，在 560 W 功率下 1 分钟和 320 W 功率下 3 分钟仅检测到 L-天冬氨酸。
