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Analysis of α -lipoic acid in drug formulations and dietary supplement preparations

Ravanić N, Filipić S., Nikolić K, Popović G, Vovk I, Simonovska B, Agbaba D

Acta Chromatographica

2009

Vol. 21, no. 3

433--441

A simple and reliable TLC method for analysis of -lipoic acid (LA) with post-chromatographic derivatisation with palladium(II) chloride immersion reagent has been developed and evaluated. Separation of LA was performed on 20 cm × 10 cm RPTLC plates with 2-propanol-methanol-acetone-water-acetic acid 6:4:2:8:0.2 ( v/v ) as mobile phase. Yellow complexes formed in situ were scanned at 375 nm. The migration distance of LA was 43.0 mm. The relationship between peak area and amount of LA applied was evaluated by use of linear (1.0–3.0 µg per band) and second-degree polynomial (0.5–5.0 µg per band) regression functions. The correlation coefficient ( r = 0.999), the limit of quantification (0.39 µg per band), recovery (98.5–105.2%), and precision (1.8–2.9%) obtained by use of the procedure were satisfactory. The method was used for analysis of LA in several drug formulations and selected dietary supplement preparations. The LA content was 99.5–101.0% in the drug formulations, 98.8–99.5% in three of five dietary supplements tested, and 48.0–185.0% in two other dietary supplements.

Simultaneous determination of loratadine and preservatives in syrups by thin-layer chromatography

Popović G., Čakar M., Agbaba D.

Acta Chromatographica

2007

No. 19

161-169

Simple, rapid, and precise densitometric TLC methods have been established for simultaneous determination of loratadine and preservatives in loratadine–sodium benzoate and loratadine–methylparaben–propylparaben mixtures. Chromatography was performed on aluminium plates precoated with silica gel 60 F254. The mobile phases were n-butyl acetate–carbon tetrachloride–acetic acid–acetonitrile 3:6:0.2:3 (v/v) for loratadine–sodium benzoate mixtures and ethyl acetate–n-hexane–methanol–ammonia–diethylamine 1:4:0.8:0.4:2 (v/v) for loratadine–methylparaben–propylparaben mixtures. Chromatographic zones were scanned in reflectance–absorbance mode at 240 nm for the former mixture and 275 nm for the latter. Relationships between peak areas and amounts of the compounds were evaluated by linear regression analysis in the concentration ranges 0.3–0.7 µg per band for loratadine, methylparaben, and sodium benzoate and 0.03–0.07 µg per band for propylparaben. Mean recovery for all the compounds varied from 98.3 to 102.5 %. Detection and quantification limits ranged from 0.004 to 0.03 and from 0.01 to 0.1 µg per band, respectively. The proposed method was used for simultaneous determination of loratadine and the preservatives in commercial medicinal syrups.