Development and Validation of a Liquid Chromatographic Method Useful for the Determination of Amino Acids in New and Commercial Alimentary Supplements

In this study, a new liquid chromatographic method with pre-column derivatization was developed and validated for the simultaneous quantification of acetylcarnitine taurinate, asparagine, potassium aspartate, asparagine and carnosine in new and commercial alimentary supplements. The effect of complex matrices was evaluated by the study of the amino acid derivatization reaction with 2,5-dimethyl-1H-pyrrole-3,4-dicarbaldehyde in placebo solutions (DPD). Experimental parameters affecting the derivatization and chromatographic separation were investigated. The reaction was carried out at room temperature for 10 min. The adducts were separated on a Synergi Hydro-RP 80 Å column using a mobile phase consisting of 11 mM aqueous tetrapropylammonium bromide (pH 3.5)/methanol by gradient elution conditions at a flow rate of 0.8 mL/min. UV absorbance detection was set at λ = 320 nm. The validation parameters such as linearity, sensitivity, accuracy, precision, specificity and ruggedness were highly satisfactory. Linear responses were obtained by placebo solutions (determination coefficient ≤ 0.9994). Intra-day precision (RSD) was ≤1.06 % for corrected peak area and ≤1.14 % for retention times (t _R) without significant differences between intra- and inter-day data. Recovery studies showed good results for all the examined compounds (from 97.72 to 101.5 %) with RSD ≤1.30 %.