Determination of glutamine and serine in rat cerebrospinal fluid using capillary electrochromatography with a modified photopolymerized sol–gel monolithic column

Capillary electrochromatographic separations of amino acid mixtures were studied using two modified porous photopolymerized sol–gel monolithic columns. One was modified with dimethyloctadecylchlorosilane (DMOS), and the other was modified with DMOS, followed by chlorotrimethylsilane to end-cap residual silanol groups. Prior to separation, amino acids were derivatized with 4-fluoro-7-nitro-2,1,3-benzoxadiazole using as a mobile phase 50 mM phosphate (pH 2.5), water, and acetonitrile in the ratio of 1:1:8. Five derivatized amino acids (Asn, Phe, Ala, Ile, and Leu) were separated within 7 min. Theoretical plate numbers varied between 58 700 and 105 000/m. This separation method with the end-capped monolithic column was applied to rat cerebrospinal fluid. The dominant amino acid found was Gln at a concentration of 420 μM along with small quantities of Ser (54 μM).