A simple, and highly sensitive chemometric-assisted spectrophotometric (A) and spectrofluorometric (B) methods were used for the determination of L-Ornithine (ORN) as such and in the alimentary supplements. ORN, an OTC marketed amino acid, is widely used as a bodybuilder that might be abused by athletes. Nucleophilic substitution reaction of ORN with 7-Chloro-4-nitrobenzo-2-oxa-1,3-diazole (NBD-Cl) was the basis of the current investigation. Plackett-Burman (PB) and Box-Behnken (BB) designs as screening and fine-tuning strategies, respectively, were instigated. Four numerical variables; reaction time (RT), temperature (Temp.), pH, reagent volume (RV) and one categorical variable, diluting solvent (DS) were considered. For the spectrophotometric approach, two responses were studied; Y1 (absorbance at 469 nm) and Y2 (absorbance at 503 nm), respectively. While the fluorescence intensity (FI, Y3) of the highly fluorescent derivative was recorded at 530 nm (λem) after excitation at 469 nm(λex). Pareto analysis, along with analysis of variance (ANOVA) were used to ascertain the significant variables (screening phase) and their domains (optimization phase). Response transformation and stepwise analysis were employed when necessary. Multiple responses’ optimization was performed using Derringer’s function and overlaid contour plots. Calibration curves were linear in the range of 20 -180 μg mL−1 and 30 – 90 pg mL-1, for methods A and B, respectively. Job’s method of continuous variation showed that the stoichiometric ratio is 2: 1 (NBD-Cl: ORN). Proposed methods were successfully applied to the dietary supplements of ORN, inferring no interference from commonly formulated adjuvants and excipients. The analytical performance of both methods was validated conforming to the ICH standards in terms of linearity, limits of detection and quantification, inter- and intra-day precisions, and accuracy.

Spectrophotometric and spectrofluorimetric determination of L-Ornithine in pure form and dietary supplements: A chemometric approach

2019 Spring National Meeting

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