tailieunhanh - HPLC for Food Analysis phần 2

Mẫu phổ chồng với quang phổ phù hợp với thư viện 994 Thực hiện phương pháp HPLC Giới hạn phát hiện 100 lượng tiêm ng, S / N = 2 tương đương với 2 ppm với 50 ml lặp lại khối lượng tiêm của RT hơn 10 chạy | Sample preparation Column Mobile phase isocratic Flow rate Column compartment Injection volume Detector filtration 300 x mm BioRad HPX 87-H 9 pm M H2SO4 ml min 65 C 10 pl UV-VWD detection wavelength 192 nm or 210 nm mAU 400 - 300 - 200 - 100- 0 0 1 1 Oxalic acid 7 Lactic acid 2 Citric acid 8 Glycerol 3 Tartaric acid 9 DEG 4 Malic acid 5 Sulfur-trioxide 6 Succinic acid 10 Acetic acid 11 Methanol 12 Ethanol 5 10 15 20 25 Time min Figure 2 Analysis of acidulants in white wine Conditions as above except Mobile phase M H2SO4 isocratic Detector UV-DAD HPLC method performance Limit of detection 100 ng injected amount S N 2 equivalent to 2 ppm with 50 pl injected volume Repeatability of RT over 10 runs areas over 10 runs 3 Figure 3 Analysis of citric acid in vodka 4. Official Methods of Analysis Food Compositions Additives Natural Contaminants 15th ed AOAC Arlington VA 1990 Vol. 2. Official Method AOAC quinic malic citric acid in cranberryjuice cocktail and applejuice. 3 Antioxidants The following compounds are used as antioxidants in food products 4 Natural antioxidants vitamin C vitamin E Synthetic antioxidants BHT butylated hydroxytoluene BHA butylated hydroxyanisole TBHQ mono-tert-butylhydroquinone THBP 2 4 5-trihydroxybutyrophenone PG propyl gallate OG octyl gallate DG dodecyl gallate Ionox-100 4-hydroxymethyl-2 6-di tert-butyl phenol NDGA nordihydroguaiaretic acid TDPA 3 3 -thiodipropionic acid ACP ascorbyl-palmitate Antioxidants may be naturally present in food or they may be formed by processes such as smoking. Examples of natural antioxidants include tocopherols vitamin E and acsorbic acid vitamin C . A second category of antioxidants comprises the wholly synthetic antioxidants. When these antioxidants are added to foodstuffs they retard the onset of rancidity by preventing the oxidative degradation of lipids. In most countries where antioxidants are permitted either singly or as combinations in foodstuffs maximum levels for these .