Development of a CE-ESI-ITMS method for the enantiomeric determination of the non-protein amino acid ornithine

Unequivocal enantiomeric determination by CE-MS2 of the non-protein amino acid ornithine (Orn), previously derivatized with FITC, was carried out in this work. A CE-tandem MS system was used to combine the potential of CE in chiral separations with the sensitivity and selectivity of tandem MS detection. The electrospray-coaxial sheath flow interface conditions were optimized and an IT analyzer working in the MS2 mode was employed to provide the best sensitivity and selectivity. Satisfactory results were obtained in terms of linearity (r2 > 0.99), precision (RSD from 1.3 to 2.3% for migration times and from 11.0 to 18.6% for corrected peak areas), and LOD (2 x 10(-9) M). Interestingly, the CE-MS2 method developed allowed a sensitivity enhancement of 100 folds with respect to UV detection. The results demonstrated the feasibility for carrying out quantitative CE-ESI-MS2 determinations of Orn enantiomers in beers. Thus, L-Orn was found in the 16 beer samples analyzed at concentrations ranging from 1 x 10(-6) to 2 x 10(-5) M, whereas the percentages of D-Orn with respect to the total amount of Orn reached values between 1.5 and 10.0%.