| Popis: |
A specific HPLC method, with an RP-C-18 column and a UV detector, for simultaneous determination of vitamin E (tochopherol, T)/T acetate (TA) in four commercial and two experimental cosmetic products is described. Three solvent systems for extraction of T/TA were assessed: isopropyl alcohol; 10:90 v/v hexane-methanol mixture (method 1); and methanol alone (method 2). The procedure was accurate, as indicated by high recovery (97.8-101.8% and 100.1-102.5% for T and TA, respectively) and precise (RSD was only 0.9-3.26% and 0.73-3.35% for T and TA, respectively). The limits of detection for T and TA were 200 and 300 ng/ml, respectively, while the limits of quantitation were 250 and 400 ng/ml, respectively. The range of reliable quantification was 5-50 μg/ml. Isopropanol as solvent resulted in a turbid extract. Method 1 and method 2 of extraction showed high recovery (98.5-99.9% and 97.2-97.9% for T and TA, respectively). After a few weeks of analysis, method 1 resulted in retention time drift, peak broadening, non-reproducible results, and progressive loss of HPLC-column integrity. Methanol alone (method 2) was equally as efficient as that of the mixture of methanol with 10% hexane (method 1) for extraction. The described analytical procedure proved to be accurate, precise, and suitable for simultaneous determination of T and TA in real commercial cosmetic products. |
