Passos Heloisa Moretti, Cieslarova Zuzana, Simionato Ana Valéria Colnaghi
Institute of Chemistry, University of Campinas-Unicamp, Campinas, SP, Brazil.
National Institute of Science and Technology in Bioanalytics, Brazil.
Electrophoresis. 2016 Jul;37(13):1923-9. doi: 10.1002/elps.201500483. Epub 2016 Mar 15.
A separation method was developed in order to quantify free amino acids in passion fruit juices using CE-UV. A selective derivatization reaction with FMOC followed by MEKC analysis was chosen due to the highly interconnected mobilities of the analytes, enabling the separation of 22 amino acids by lipophilicity differences, as will be further discussed. To achieve such results, the method was optimized concerning BGE composition (concentrations, pH, and addition of organic modifier) and running conditions (temperature and applied voltage). The optimized running conditions were: a BGE composed by 60 mmol/L borate buffer at pH 10.1, 30 mmol/L SDS and 5 % methanol; running for 40 min at 23°C and 25 kV. The method was validated and applied on eight brands plus one fresh natural juice, detecting 12 amino acids. Quantification of six analytes combined with principal component analysis was capable to characterize different types of juices and showed potential to detect adulteration on industrial juices. Glutamic acid was found to be the most concentrated amino acid in all juices, exceeding 1 g/L in all samples and was also crucial for the correct classification of a natural juice, which presented a concentration of 22 g/L.
为了使用毛细管电泳-紫外检测法（CE-UV）对西番莲果汁中的游离氨基酸进行定量分析，开发了一种分离方法。由于分析物的迁移率高度相关，因此选择了与芴甲氧羰基（FMOC）的选择性衍生化反应，随后进行胶束电动色谱（MEKC）分析，通过亲脂性差异实现22种氨基酸的分离，这将在后面进一步讨论。为了获得这样的结果，对方法进行了优化，包括背景电解质（BGE）组成（浓度、pH值和有机改性剂的添加）和运行条件（温度和施加电压）。优化后的运行条件为：由pH值为10.1的60 mmol/L硼酸盐缓冲液、30 mmol/L十二烷基硫酸钠（SDS）和5%甲醇组成的BGE；在23°C和25 kV下运行40分钟。该方法经过验证，并应用于八个品牌的果汁以及一种新鲜天然果汁，检测到12种氨基酸。六种分析物的定量分析结合主成分分析能够对不同类型的果汁进行表征，并显示出检测工业果汁掺假的潜力。发现谷氨酸是所有果汁中含量最高的氨基酸，所有样品中的含量均超过1 g/L，对于一种浓度为22 g/L的天然果汁的正确分类也至关重要。
