Proline

Hydroxyproline seems to be the most promising amino acid used in carbon dating when isolated from bone collagen. Separation of amino acids is challenging, especially without the use of ions or inorganic buffers that can interfere with Mass spectrometer (MS) or contaminate the sample with modern carbon. Amino acids are also not retained in reverse-phase chromatography. The ideal solution would be using water only to separate the amino acids. This would allow a direct coupling to MS. We were able to separate hydroxyproline from proline and other simple amino acids like glycine and alanine in HPLC on Newcrom AH column using water only as a mobile phase. Using water also allowed UV detection at 205 nm which can’t be done if using a buffer based on acetic or formic acid.
See more information on radiocarbon dating here.
The same method can be modified to get symmetrical peaks and higher efficiency if a mobile phase with ionic modifier such as formic acid is used.

Application Notes: Amino acids are polar ionic compounds which are not retained on reversed-phase column without ion-pairing reagent. In our application, lysine and arginine can be separated from other amino acids. Amino acids with a pH between 3 and 5 and with one basic and one acidic group become very polar. Therefore these amino acids don’t have strong ion-exchange interaction with Primesep C stationary phase. Amino acids with two amino groups still carry positive net charge and can interact with stationary phase by cations-exchange mechanism. pH variation of the mobile phase can be an effective tool to adjust selectivity of separation for zwitter-ionic, basic and acidic compounds. This method can be used for separation of mono-charged compounds from compounds having an extra charge.

Application Columns: Primesep C
Application compounds: Aspartic acid, Glutamic acid, Aspargine, Glycine, Proline, Alanine, Phenylalanine, Tyrosine, Leucine, Lysine, Arginine
Detection technique: UV, LC/MS, ELSD/CAD

Polar amino acids are very often used as components of vitamin and supplement composition. Analysis of such complex composition is a challenging task. In this application, 5 amino acids (asparagine, glutamic acid, proline and arginine) and two preservatives (methyl paraben and propyl paraben) are separated on a Primesep 100 reversed-phase cation-exchange column with LC/MS compatible mobile phase. Method does not require ion-pairing reagent in the mobile phase. Compounds are monitored by ELSD and UV. Method is validated for quantitation of underivatized amino acids in complex mixtures. The method is simple and robust and can be used for analysis of various vitamin formulations.

Primesep 100 separates the components of a Swiss cheese extract by HPLC using cation exchange and reversed phase as retention mechanisms. The amino acids, glutamic acid and proline, as well as glycine betaine were resolved in less than 10 minutes. A mobile phase gradient of water, acetonitrile (MeCN, ACN,) and phosphoric acid (H3PO4) and ultraviolet (UV) detection was used.