HPLC Methods For Determining Synthetic Colorant, Preservative And Sweetener Added Into Wine

The abuse of food additives has already been a serious threat to food safety. In Chinese national standard GB15037-2006 of"wine", synthetic colorant, sweetener, essence and/or thickener are not permitted to add into wine, and the added amounts of preservative in wine are also strictly limited. At present, the detection of additives in wine primarily refers to the methods used in beverage and imitation wine. However, considering the chemical components in wine are more complex than those in imitation wine, direct detection of synthetic colorant, preservative and sweetener in wine using the high-performance liquid chromatography (HPLC) method used in imitation wine, always leads to the increase of the detection error and the decrease of sensitivity. Therefore, it is essential to establish new HPLC methods, specially used in wine for detection of synthetic colorant, preservative and sweetener, so as to ensure the quality and safety of wine.In this study, the pre-treatment methods of 4 synthetic colorants (tartrazine, sunset yellow, carmine and amaranth), 2 preservatives (benzoic acid and sorbic acid) and saccharin sodium were comprehensively examined, their HPLC detection conditions were optimized respectively, and some inferior wines were also investigated. The main results obtained are as following:1. A method was established for simultaneous determination of four synthetic colorants in wine by a HPLC method with variable wavelength detector.Comparing the separation effects of different wine sample pre-treatment methods and optimizing the HPLC detection conditions, a HPLC method was established for simultaneous determination of tartrazine, sunset yellow, carmine and amaranth in wine with variable wavelength detector. The best wine samples pre-treatment method is by polyamide absorption. The optical chromatographic conditions are: 5μm particle size reversed phase column Agilent ZORBAX SB-C18 (4.6×250 mm) was used and the mobile phase consisted of solution A (methanol) and solution B (ammonium acetate 0.02 mol/L) with gradient elution and variable wavelength detection, and the detection wavelengths for tartrazine, sunset yellow, carmine and amaranth were 430 nm (0 ~ 2.2 min), 230 nm (2.50 ~ 3.95 min), 480 nm (3.95 ~ 5.00 min), 480 nm (3.95 ~ 5.00 min), respectively. The flow rate was 1.0 mL/min, column temperature 35 oC, detection time 5 min, and the injection volume was 20μL. When the four standards of the colorants were added to the wine respectively and precision test, the average relative standard deviation (RSD) was 0.73% ~ 1.51%, and the average recovery was 87.83% ~ 107.42%.2. A HPLC method for simultaneous determination of benzoin acid, sorbic acid and saccharin sodium in wine was determined.Based on Chinese national HPLC method for detection of benzoin acid, sorbic acid and saccharin sodium used in imitation wine (GB/T5009.29-2003), the separation effects of different wine sample pre-treatment methods were compared and the HPLC detection conditions were optimized, and a HPLC method was determined for simultaneous determination of benzoin acid, sorbic acid and saccharin sodium in wine. Wine samples were best pre-treated by means of concentration and re-extraction. The optimal chromatographic conditions are: 5μm particle size reversed phase column Agilent TC-C18 (4.6×250 mm) was used, using solution A (methanol) and solution B (ammonium acetate 0.02 mol/L) (A : B = 30 : 70, v/v) as the mobile phase with isocratic elution. The flow rate was 1.0 mL/min, detection wavelength was 230 nm, column temperature 30 oC, and the injection volume was 10μL. When the standards of benzoin acid, sorbic acid and saccharin sodium were added to the wine respectively and precision test, the average relative standard deviation (RSD) was 0.89% ~ 1.38%, and the average recovery was 91% ~ 103%. The developed method is simply fast, reliable and reproducible.On the other hand, some useful methods were investigated for fast determining some fake and inferior wines. The fake and inferior wines made with low juice content can be identified by means of changing the pH value of wine samples or the adding ways of sulfur dioxide. The method that uses the color reaction developed by Folin-Ciocalteu and gallic acid standard solution (400 mg/L) to distinguish inferior wines may only be applied to inferior wines with grape juice content below 20%.