A interlaboratory study was conducted to evaluate a liquid chromatographic (LC) procedure for the determination of total vitamin C in foods at levels of 5–60 mg/100 g. Emphasis was placed on fruit juices, although selected foods were also included in the study. Following dissolution of sample in water, endogenous dehydroascorbic acid was converted to ascorbic acid by precolumn reduction with dithiothreitol at neutral pH. Total ascorbate was determined by C18 reversed-phase LC with a phosphate eluent at pH 2.5, incorporating dithiothreitol to maintain vitamin C in the reduced form, and UV detection at 254 nm. Seven types of fruit juices and foods were tested by 19 collaborators in 7 countries. Three duplicate juices and foods met the criteria for Youden pairs and yielded repeatability relative standard deviation of 5.80–14.66%. Reproducibility relative standard deviation ranged from 6.36 to 35.54% (n = 10) with HORRAT values of 0.82–4.04. The LC method is suitable for routine use in fruit products and foods containing >5 mg/100 g vitamin C and is recommended for further validation by AOAC INTERNATIONAL and International Fruit Juice Union.
An AOAC International-International Union of Pure and Applied Chemistry-International Fruit Juice Union (AOAC-IUPAC-IFJU) collaborative study was conducted to evaluate a liquid chromatographic (LC) procedure for determination of patulin in apple juice. Patulin is a mold metabolite found naturally in rotting apples. Patulin is extracted with ethyl acetate, treated with sodium carbonate solution, and determined by reversed-phase LC with UV detection at 254 or 276 nm. Water, water-tetrahydrofuran, or water-acetonitrile was used as mobile phase. Levels determined in spiked test samples were 20, 50,100, and 200 μg/L. A test sample naturally contaminated at 31 μg/L was also included. Twenty-two collaborators in 10 countries analyzed 12 test samples of apple juice. Recoveries averaged 96%, with a range of 91-108%. Repeatability relative standard deviations (RSDr) ranged from 10.9 to 53.8%. The reproducibility relative standard deviation (RSDR) ranged from 15.1 to 68.8%. The LC method for determination of patulin in apple juice has been adopted first action by AOAC INTERNATIONAL.
On p. 378. Fig. 6, the lower left axis shonld read Residue Rotation, [R'] ; the right axis On p. 394, procedure 6, line 6 should read m.p. (corr.) 194-195°C.; [a]'," = + 12.75' should read Molar Ellipticity, 0.(c = 1.17, glacial aretic acid).
Some Optical Properties of Poly-1-benzyl-L-histidine snd Poly-L-histidineHiopolymers, 1, 277-294 (1sCi3)
A series of instrumental analyses is used for verification of the authenticity of orange juice: liquid chromatography for sugars, UV-visible spectrophotometry for absorbance measurements, stable isotope ratio analysis of δ13C and δ18O values, and atomic absorption spectrophotometry for potassium and sodium analyses. All authentic orange juices possess positive δ18O values, while those of ground water and water in beet invert syrups are negative. Hence, addition of either to orange juices decreases δ18O values, and allows detection of nonauthentic products.
A series of instrumental analyses is described for verification of apple juice authenticity. Liquid chromatography is used to determine sugars and individual phenolics, atomic absorption spectroscopy is used to determine potassium, standard AOAC methods are used to test for polyphenolics arid formol indexes, and stable carbon isotope ratio analysis (SCIRA) is used to detect high fructose corn syrup. These tests will identify fraudulent but not poorly processed apple juice.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.