Fast derivatization of the non‐protein amino acid ornithine with FITC using an ultrasound probe prior to enantiomeric determination in food supplements by EKC

Abstract

An EKC method for the determination of ornithine (Orn) enantiomers has been developed after a fast pre-capillary derivatization with FITC. The derivatization step was needed to provide a chemical moiety to the Orn molecule, enabling a sensitive UV detection and the interaction with the CDs used as chiral selectors. To accelerate the derivatization reaction, an ultrasound probe was used. For the development of the chiral method, the influence of different experimental conditions (type and concentration of the chiral selector, temperature, and separation voltage) was investigated. Due to the anionic nature of the analyte (FITC-Orn), five neutral CDs were employed as chiral selectors. The native gamma-CD showed the highest chiral separation power, observing that a low concentration of this CD (1 mM), using a working temperature of 25 degrees C and a separation voltage of 20 kV, enabled to obtain the highest enantioresolution for Orn and its separation from other amino acids usually present in food supplements. After optimizing the method for the preconditioning of the capillary, the analytical characteristics of the chiral method were established. Linearity, LOD and LOQ, precision, and accuracy were evaluated previously to the determination of Orn enantiomers contained in ten commercial food supplements. No interferences from other amino acids present in these samples were observed.

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

“…g-CD was selected as chiral selector based on a previous work [17], in which we already demonstrated the better possibilities of g-CD to separate FITC-amino acid enantiomers compared with other chiral selectors, showing its applicability to the determination of Orn enantiomers in different dietary supplements. However, this method had a limitation, the numerous signals originated by the derivatizing agent, which provided low selectivity and made it unsuitable for samples with complex matrices.…”

“…When the tip of the probe was set at 3 mm from the bottom of the solution, 10 min of continuous sonication at amplitude of 100% (corresponding to the maximum energy of sonication) was used according to the procedure previously optimized in our laboratory [17]. Following this procedure, solutions were not protected from the light, because the same results were observed whether vials were covered or not by an aluminum film.…”

“…Finally, an optimization of the fragmentation in MS 2 experiments was performed for a range of fragmentation amplitudes from 1.0 to 3.0 V and monitoring the intensities of the fragment ions to reach a maximum response, being selected a value of 1.5 V. The last conditions selected for the CE-MS 2 system decreased the enantiomeric resolution of Orn achieved in the previous work using CE-UV [17]. For this reason, the study of some CE parameters with influence on the enantioseparation was performed.…”

“…Thus, several works have reported the enantiomeric separation of Orn by CE [15][16][17][18][19]. Some of them have been developed in our research group, reaching analysis times lower than 15 min, even showing their potential in food analysis [17][18][19].…”

A rapid method for the in-field analysis of amphetamines employing the Agilent Bioanalyzer

“…28,29 Typical derivatisation times with FITC have been up to 12 hours, with recent attempts to shorten the reaction time. Dominguez-Vega et al 30 described an accelerated FITC derivatisation of the amino acid ornithine. The reaction time was reduced from 16 hours to 10 minutes by the use of an ultrasonic probe.…”