Enantiomeric separation of Free L- and D-Amino Acids in Hydrolyzed Protein Fertilizers by Capillary Electrophoresis Tandem Mass Spectrometry

L-amino acids play a part in many physiological processes in plants. However, while L-amino acids are biologically active, the metabolism role of D-amino acids in plants is still doubtful, and the few existing studies on this topic indicate undesired agronomic effects. The enantiomeric separation of free amino acids contained in different hydrolyzed protein fertilizers used as biostimulants was achieved. Two capillary electrophoresis-tandem mass spectrometry (CE-MS2) methods were optimized in this work using cyclodextrins (CDs) as chiral selectors. The developed methodologies were applied to the analysis of samples obtained through different kinds of hydrolysis treatments in order to evaluate the presence of D-amino acids. The results corroborated the absence or almost negligible presence of enantiomeric conversions of the L-amino acids in the case of fertilizers obtained by enzymatic hydrolysis (Terra-Sorb®), as well as the high racemisation rate for those obtained through a chemical hydrolysis.