Comparison of DL-Amino Acid Labeling Kit and Achiral Labeling Reagents
A comparison of the below labeling reagents was performed using pre-column derivatization.
Optical separation of DL enantiomers
Labeled DL-phenylalanine was analyzed using a C18 column. The labeling reagent in the DL-Amino Acid Labeling Kit has a chiral carbon, resulting in the labeled D and L forms being diastereomers. This makes them separable on C18 columns.
* Generally, fluorescence detection is used for amino acids labeled with o-phthalaldehyde.
Detection sensitivity with mass spectrometry (MS)
Detection sensitivity was compared using labeled L-phenylalanine as the sample. Both the DL-Amino Acid Labeling Kit and dabsyl chloride had high MS sensitivity, due to their easily ionizable structures.
Stability of labeled samples
Labeled L-phenylalanine was analyzed by HPLC 1, 3, and 7 days after labeling. The sample labeled with o-phthalaldehyde was not stable, and therefore should not be labeled manually, but rather using online analysis within the instrument.
| Days after labeling | DL-Amino Acid Labeling Kit | Dabsyl chloride | o-Phthalaldehyde |
|---|---|---|---|
| 1 | 100% | 100% | 100% |
| 3 | 113% | 95% | 0% |
| 7 | 106% | 96% | 0% |
* Analysis conditions are as in "Optical separation of DL enantiomers". The peak area measured after 1 day was taken as 100%. Samples were stored refrigerated.
