NIR spectroscopy and partial least-squares regression for determination of natural alpha-tocopherol in vegetable oils.

Near-infrared (NIR) spectroscopy and partial least-square regression were used for determination of alpha-tocopherol in edible oils after extraction with ethanol. The standard error of calibration and the standard error of prediction were calculated for evaluation of the calibration models. The chemometric calibration model was prepared in spectral region 6500-4500 cm(-1) for standard alpha-tocopherol solutions (0.54-53.54 mg/mL). Obtained mean concentrations of natural alpha-tocopherol in different types of oils varied from 17.53 to 57.10 mg/100 g. Net analyte signal calculation was used to estimate detection limit (DL = 0.12 mg/mL), quantification limit (QL = 0.40 mg/mL), sensitivity (SEN = 0.045 mg/mL), and selectivity (SEL ranged between 0.24 and 0.54% of the measured reflectance signal) of the proposed NIR method. The comparable precision (RSD = 0.68-2.80% and 0.79-3.06%) and accuracy (recovery, 97.2-102.4% and 96.8-103.2%) for the proposed NIR and standard HPLC methods, demonstrate the benefit of the NIR method in the routine analysis of alpha-tocopherol in vegetable oils.

Electrochemical determination of oxytetracycline in veterinary drugs.

Conductometric, potentiometric and cyclic voltammetric (CV) titration methods are proposed for determination of oxytetracycline (OTC), commonly used in veterinary. The electrochemical titration of OTC hydrochloride with NH(4)Mo(7)O(24), NaVO(3), NaOH, AgNO(3) and FeCl(3) as titrants are reported. The proposed methods were found to be highly precise, having a relative standard deviation (R.S.D.) below 1.0%. Proposed electrochemical titrations were successfully applied to the assay of commercial preparations: Tetrox, Tetramutin OT and Neox, containing the above-mentioned antibiotics. The validity of the methods was tested by the recovery studies of standard addition to pharmaceuticals and results were found to be satisfactory.