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Blackberry wine, a popular fruit wine, is a product of yeast fermentation of natural sugars present in blackberry juice, well known natural source of vitamins. It was shown that blackberry variety, technology of manufactoring and duration of wine storage have influence on amounts of vitamins present in wine. Today, HPLC methods are the most often used for the determination of water-soluble vitamins for evaluation and quality control of wines. Major advantage of these chromatographic methods is their ability to separate different forms of vitamins from very complicated matrix, such as blackberry wine. The contents of ascorbic acid, thiamine, riboflavin, nicotinic acid, pyridoxine and folic acid were determined in fifteen samples of blackberry wine from different regions of Croatia. All samples were filtered through Minisart RC4, 0.45 µ m filters (Sartorius), which did not retain any of the analytes. The samples were injected after filtration or after dilution with 1 M phosphate buffer, pH 5.5. The chromatographic system consisted of a Dionex HPLC Pump P680, Automated Sample Injector ASI-100, Termostatted Column Compartment TCC-100 and UVD340U PDA Detector. Vitamins were separated on a Zorbax SB-C18 (250 x 4.6 mm, 5 µ m ; Agilent Technologies) with suitable guard column. The following solvents were used: solvent A (50 mM sodium phosphate buffer (pH 2.5):MeOH, 90:10, v/v) and solvent B (50 mM sodium phosphate buffer (pH 2.5):MeOH, 10:90, v/v). The mobile phase was filtered and degassed ultrasonically prior to use. The gradient was linearly changed from 0 to 70% B in 22 min, with a post-run time of 3 min (100% B) and a constant flow rate of 1 mL min-1. The column temperature was maintained at 20 °C, the injection volume was 10 µ ; l and the detector was set at 223 nm for folic acid and riboflavin, 245 nm for thiamine and ascorbic acid, 268 nm for nicotinic acid and 292 nm for pyridoxine. Vitamin standards were used to generate characteristic UV-VIS spectra and calibration curves. The analyses were performed in triplicate. Optimized HPLC method with UV detection was validated through linearity, sensitivity, selectivity and repeatability, and it was shown that this method can be used for routine analysis of six vitamins in blackberry wine. |
