Department of Analytical Chemistry, Faculty of Chemistry, University of Alcalá, Carretera Madrid-Barcelona, Km 33,600, 28871 Alcalá de Henares, Madrid, Spain.
J Agric Food Chem. 2013 May 29;61(21):5022-30. doi: 10.1021/jf4013345. Epub 2013 May 17.
Two capillary electrophoresis-tandem mass spectrometry (CE-MS(2)) methods were optimized in this work using cyclodextrins (CDs) as chiral selectors in order to determine the degree of racemization of the free amino acids contained in different hydrolyzed protein fertilizers used as plant biostimulants. The methodologies developed were characterized by the specificity of MS(2) experiments enabling the identification of all protein amino acids, except for cysteine. The enantiomeric separation of up to 14 amino acids was achieved with resolutions above 1.0 and limits of detection between 0.02 and 0.8 μM. The methods were applied to the analysis of complex samples such as hydrolyzed protein fertilizers to evaluate the presence of d-amino acids after different kinds of hydrolysis treatments. The results corroborated the absence or almost negligible presence of enantiomeric conversions of the L-amino acids into D-amino acids in the case of fertilizers obtained by enzymatic hydrolysis, as well as the high racemization rate for those obtained through a chemical hydrolysis.
本文使用环糊精（CDs）作为手性选择剂，优化了两种毛细管电泳-串联质谱（CE-MS(2)）方法，旨在测定用作植物生物刺激剂的不同水解蛋白肥料中所含游离氨基酸的外消旋程度。所开发的方法通过 MS(2)实验的特异性进行了表征，能够识别除半胱氨酸以外的所有蛋白质氨基酸。通过分辨率高于 1.0 和检测限在 0.02 和 0.8 μM 之间，实现了多达 14 种氨基酸的对映体分离。该方法应用于复杂样品如水解蛋白肥料的分析，以评估不同水解处理后 d-氨基酸的存在情况。结果证实，在通过酶水解获得的肥料中，L-氨基酸向 D-氨基酸的对映体转化几乎不存在或可以忽略不计，而通过化学水解获得的肥料则具有很高的外消旋率。
