Application of achiral-chiral two-dimensional HPLC for separation of phenylalanine and tryptophan enantiomers in dietary supplement.

This study developed a two-dimensional heart-cutting LC method for the separation of amino acid enantiomers. Two approaches for achiral separation of amino acids, phenylalanine and tryptophan, were selected. Amino acids were separated on C18 or hydrophilic interaction liquid chromatography (HILIC) columns in first dimension after their enantiomer separation on a teicoplanin chiral column in second dimension. Mobile phases for both separation systems were optimized by testing different types of organic modifiers, concentrations of ion-pair agent (sodium 1-octanesulfonate), and ionic modifier (ammonium acetate). The resolution of enantiomers higher than 1.5 for both amino acids was achieved using a C18-teicoplanin coupled column separation system with mobile phases methanol/2 mM sodium 1-octanesulfonate (10:90 and 75:25, step gradient between achiral and chiral columns, respectively). The lower resolution of amino acid enantiomers (RS ˃ 0.9), but higher column efficiency, was achieved on a HILIC-teicoplanin separation system with mobile phases acetonitrile/50 mM ammonium acetate (90:10 and 80:20, step gradient between achiral and chiral columns, respectively). The developed heart-cutting 2D-LC methods were validated in terms of linearity, limit of detection, limit of quantification, precision, and accuracy. The results suggested that the developed methods were applicable for the simultaneous determination of amino acid enantiomers in the dietary supplement. The sample contained l-phenylalanine and l-tryptophan.

Determination of panthenol enantiomers in cosmetic preparations using an achiral-chiral-coupled column HPLC system.

A new high-performance liquid chromatography (HPLC) method for separation and determination of panthenol enantiomers in hair care products was developed. Two types of detectors, low-wavelength ultraviolet (UV) and polarimetric, were used. Optimized conditions consisted of coupled achiral, amino type, and chiral, amylose tris(3,5-dimethylphenylcarbamate), stationary phases, mixture of n-hexane/ethanol (60:40, v/v) as mobile phase under isocratic conditions and flow rate 0.8 cm3 min-1 . The effect of column temperature on retention and resolution of enantiomers was studied. The analysis runtime was 10 minutes, and the average retention times for d- and l-panthenol were 7.10 ±0.1 minutes and 8.21 ±0.2 minutes, respectively. The resolution of enantiomers on coupled achiral-chiral columns was Rs = 2.7. The solid-phase extraction method was employed for extraction and purification of analytes. The validated method was selective, accurate, and linear (R2 > .998) over the concentration range of 0.001 to 1.0 mg cm-3 for both enantiomeric forms. The limits of detection (LOD) and quantitation (LOQ) of each enantiomer were 0.3 and 1.0 µg cm-3 , respectively. The results demonstrated the occurrence of d-panthenol in hair care products.

[Separation of phenylalanine and methionine enantiomers by HPLC method: a comparison of stationary phase types]. / Separácia enantiomérov fenylalanínu a metionínu metódou HPLC: porovnanie typov stacionárnych fáz.

The paper deals with enantioselective separation of amino acids by the high performance liquid chromatography method. Separations of enantiomeric forms were tested on the chiral stationary phases based on ß-cyclodextrine, isopropyl carbamate cyclofructan 6, and the macrocyclic antibiotic teicoplanin. The best enantioseparation was obtained on the teicoplanin-based chiral stationary phase in the reversed-phase mode. UV spectrophotometric detection at 210 nm was used for detection of amino acids. The method was validated with respect to linearity, precision, limit of detection, limit of quantitation, and recovery. Limits of quantitation for phenylalanine and methionine enantiomers were 0.3 and 0.2 µg.ml-1, respectively. The HPLC method with teicoplanin-based chiral stationary phase was applied for analysis of dietary supplements.Key words: separation of enantiomers HPLC phenylalanine methionine.