In this paper, the development and application of a multiple heart‐cutting achiral–chiral LC–LC method (mLC–LC) for the analysis of dansylated (Dns) branched‐chain amino acids in commercial tablets are described. In the first dimension, a Waters Xbridge RP C18 achiral column was used under gradient conditions with buffered aqueous solution and acetonitrile. The elution order Dns‐valine (Dns‐Val) < Dns‐isoleucine (Dns‐Ile) < Dns‐leucine (Dns‐Leu) turned out with full resolution between adjacent peaks: 7.25 and 1.50 for the Val/Ile and the Ile/Leu pairs, respectively. A “research” validation study was performed, revealing high accuracy (Recovery%) and precision (RSD%) using two external set solutions, respectively, in the range 93.7%–104.1% and 0.4%–3.2%. The C18 column was connected via a two‐position six‐port switching valve to the quinidine‐based Chiralpak quinidine‐anion‐exchange chiral column. A water/acetonitrile, 30/70 (v/v) with 50 mM ammonium acetate (apparent pH of 5.5) eluent allowed getting the three enantiomers’ pairs resolved: RS equal to 4.3 for Dns‐Val and Dns‐Ile, and 1.7 for Dns‐Leu. The application of the mLC‐LC method confirmed that the content of Val, Ile, and Leu in the tablets was compliant with that labeled by the producer. Only l‐enantiomers were found in the food supplement, as confirmed by LC–MS/MS analysis.

中文翻译：

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开发一种易于设置的多重中心切割非手性-手性 LC-LC 方法，用于分析商业片剂中的支链氨基酸

本文描述了用于分析商业片剂中丹磺酰化（Dns）支链氨基酸的多重中心切割非手性-手性LC-LC方法（mLC-LC）的开发和应用。在第一维中，在梯度条件下使用Waters Xbridge RP C18非手性柱，使用缓冲水溶液和乙腈。洗脱顺序 Dns-缬氨酸 (Dns-Val) < Dns-异亮氨酸 (Dns-Ile) < Dns-亮氨酸 (Dns-Leu) 结果显示相邻峰之间具有全分辨率：Val/Ile 和 Ile/ 为 7.25 和 1.50分别为亮氨酸对。进行了一项“研究”验证研究，揭示了使用两种外部设定解决方案的高精度（回收率％）和精密度（RSD％），分别在93.7％–104.1％和0.4％–3.2％的范围内。C18 色谱柱通过两位六通切换阀连接到基于奎尼丁的 Chiralpak 奎尼丁阴离子交换手性色谱柱。水/乙腈，30/70 (v/v) 和 50 mM 醋酸铵（表观 pH 为 5.5）洗脱液可以解析三种对映体对：右SDns-Val 和 Dns-Ile 等于 4.3，Dns-Leu 等于 1.7。mLC-LC方法的应用证实片剂中Val、Ile和Leu的含量与生产商标注的相符。仅有的我‐经 LC-MS/MS 分析证实，食品补充剂中发现了对映异构体。