The proposed analytical method reports the separation and quantification of 21 amino acids including l-citrulline from fresh vegetables and commercial juices using a C8 column. Optimal separation conditions for amino acids analysis were obtained with 20 mM sodium acetate (solvent A) and water with organic modifier acetonitrile and methanol (solvent B; 18/50/32 V/V). The ideal pH and column temperature were found to be 5.40 and 35 °C, respectively. The LOD and LOQ values were obtained in the range of 0.02-0.19 ng/mL and 0.04-0.39 ng/mL for all amino acids respectively. Relative standard deviations (RSD) of intraday and interday analysis were found to be <2.7% and 7.9%, respectively. The recovery of amino acids were found be satisfactory for all the tested crops. The developed method was successfully used for the quantification of amino acids in six fresh vegetable juices including watermelon, cucumber, celery, calabaza squash, zucchini squash, yellow squash and commercial juices. Multivariate analysis was used to determine the significant differences in the amino acids profiles. l-citrulline content was highest in fresh watermelon juice (716.57 ± 24.80 μg/mL) and commercial watermelon lime juice (826.48 ± 34.48 μg/mL). The optimized analytical method is rapid, sensitive, accurate and reproducible for analysis of free amino acids including l-citrulline from different vegetable juices and other food products. To the best of our knowledge, this is the first report to separate OPA derivatives of amino acids using C8 column from watermelon, cucumber, zucchini squash, yellow squash, calabaza squash, and celery in a HPLC-FLD system.

中文翻译：

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一种灵敏的 HPLC-FLD 方法结合多元分析测定富含 l-瓜氨酸的蔬菜中的氨基酸

所提出的分析方法报告了使用 C8 色谱柱从新鲜蔬菜和商业果汁中分离和定量 21 种氨基酸，包括 l-瓜氨酸。使用 20 mM 乙酸钠（溶剂 A）和水与有机改性剂乙腈和甲醇（溶剂 B；18/50/32 V/V）获得了氨基酸分析的最佳分离条件。发现理想的 pH 值和柱温分别为 5.40 和 35 °C。所有氨基酸的 LOD 和 LOQ 值分别在 0.02-0.19 ng/mL 和 0.04-0.39 ng/mL 范围内。发现日内和日间分析的相对标准偏差 (RSD) 分别为 <2.7% 和 7.9%。所有受试作物的氨基酸回收率均令人满意。所开发的方法成功地用于六种新鲜蔬菜汁中氨基酸的定量，包括西瓜、黄瓜、芹菜、calabaza 南瓜、西葫芦、黄南瓜和商业果汁。多变量分析用于确定氨基酸谱的显着差异。新鲜西瓜汁 (716.57 ± 24.80 μg/mL) 和商业西瓜酸橙汁 (826.48 ± 34.48 μg/mL) 中的 l-瓜氨酸含量最高。优化的分析方法快速、灵敏、准确且重现性好，可用于分析不同蔬菜汁和其他食品中的游离氨基酸，包括 l-瓜氨酸。据我们所知，这是第一个使用 C8 柱从西瓜、黄瓜、西葫芦、黄南瓜、calabaza 南瓜中分离氨基酸 OPA 衍生物的报告，