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1.
Vitamin D is determined in preparations containing other fat-soluble vitamins by high performance liquid chromatography (HPLC). The unsaponifiable residue is extracted and separated from interferences by reverse phase chromatography; the fraction corresponding to vitamin D3 is collected and quantitated using normal phase chromatography (amylalcohol-n-hexane as mobile phase) by measuring the vitamin D3 and pre-vitamin D3 peaks at 254 nm. Previtamin D3 content is calculated as vitamin D3 with a conversion factor (determined on the equipment used). Application of the method to vitamin AD3 mixtures in oils gives 98-102% recovery. The reproducibility, using an external standard, is 2-3%, calculated as the coefficient of variation; with an internal standard, the coefficient of variation is 1-1.5%. The method measures potential vitamin D3 content in preparations containing greater than or equal to 200 IU/g in the presence of all known vitamin D3 isomers, vitamin A, and vitamin E.  相似文献   

2.
A high performance liquid chromatographic (HPLC) method for vitamin D in pet foods and feeds at low concentrations (2-8 IU/g = 50-200 ppb) was studied collaboratively. The procedure consists of the following purification steps: saponification, extraction of the unsaponifiable fraction, chromatography on alumina, cleanup on reverse phase HPLC, and quantitation with straight phase HPLC. The original method, developed by Knapstein, was simplified by deleting the quantitative TLC step. Six coded samples were distributed to 31 laboratories, along with a known sample containing 15 IU/g to allow practice of the rather complicated procedure. Eighteen collaborators returned their results. Results for the spiked samples show good recovery. The estimates of repeatability and reproducibility are 0.96 and 2.2 IU/g for spiked samples and 1.5 and 3.1 IU/g for commercial samples, respectively, which are considered acceptable for these low concentrations. The method has been adopted official first action.  相似文献   

3.
The official first action method for determining vitamin D in multivitamin preparations was modified. The method was collaboratively studied by 7 laboratories, using 6 preparations in oil. The preparations consisted of vitamin D at various levels and at various ratios (in w/w) in vitamin A. Three samples contained cholecalciferol and 3 samples contained vitamin D3 from vitamin D3 resin. After outliers were eliminated by the Dixon test, data were analyzed and averages were compared with amounts of vitamin D known to be in each sample. For samples with vitamin D: vitamin A ratios of 1:0.5, 1:5, and 1:10, the mean vitamin D recoveries were 98.8, 94.6, and 90.7%, respectively. The method has been adopted as official final action.  相似文献   

4.
A method is described for the determination of vitamins D2 + D3 in milk- and soy-based infant formula. Vitamins D2 and D3 are extracted from the saponified sample and converted to isotachysterols with acidified butanol. Reverse-phase liquid chromatography (LC) is used to remove interferences, and total vitamin D is quantitated using normal-phase LC. Recoveries of spiked samples averaged 97.6% for milk-based infant formula, and 98.8% for soy-based infant formula. This method quantitates vitamin D2 + D3 in infant formulas containing as low as 40 IU/qt when prepared according to label direction.  相似文献   

5.
In 1971, a chemical method for the assay of vitamin D in concentrates containing only vitamin D was collaboratively studied by 14 laboratories, using 6 different samples from 2 European manufacturers. On the basis of these results, the laboratories were divided into 2 groups: 5 with significant laboratory biases of greater than or equal to 2%, and 9 laboratories with nonsignificant bias. The 9 laboratories were subdivided into 2 groups which differed significantly as to reproducibility within laboratories. The reproducibility between laboratories, expressed as a standard deviation in per cent with 95% confidence limits, was 1.2% (confidence range 0.6-7.3) and 4.7% (confidence range 2.4-29.3) for 3 and 6 laboratories, respectively. A second collaborative test was performed in 1974, using 12 vitamin D resin samples in oil from 3 United States manufacturers, to compare 2 chemical vitamin D assay methods (with and without maleic anhydride) and to compare results from the chemical and biological methods; 9 laboratories participated in the chemical method study and 3 in the rat bioassay study. The correlation of results of the chemical method including maleic anhydride treatment and the rat bioassays was satisfactory. The reproducibility of the chemical method was about the same as that in the first collaborative test.  相似文献   

6.
Vitamin D2 or vitamin D3 is determined by liquid chromatography (LC) in milk and infant formula. Vitamin D is extracted from the saponified sample, passed through an amino-cyano LC cleanup column to remove major interferences, and quantitated using normal phase LC. Within-day precision is 4.5% relative standard deviation (RSD); the overall method RSD (reflecting technician-to-technician, day-to-day, and within-day variability) is 7.7%. Overspike recoveries averaged 97% for milk, 98% for milk-based infant formula, and 93% for soy-based infant formula. The performance of the method is compared with that of the official AOAC vitamin D method (rat bioassay). The method is applicable to the determination of vitamin D in milk and in the major milk- and soy-based infant formulas available in the United States. The method can quantitate (but not distinguish) either vitamin D2 or vitamin D3. The method is applicable to milk and infant formula samples containing between 100 and 1500 IU vitamin D/L. Sample throughput is between 4 and 8 replicates per day.  相似文献   

7.
A high-pressur liquid chromatographic (HPLC) procedure has been developed for the determination of vitamin D3 in resins, oils, dry concentrates, and dry concentrates containing vitamin A. Specificity of the method for vitamin D3 in the presence of isomers and other related constituents was shown by ultimate recovery of the vitamin D3 and the individual constituents and their characterization by other methods such as ultraviolet spectrophotometry. Precision and accuracy are within 2%, and as many as 20 determinations may be completed in a working day. Excellent agreement with the official AOAC biological assay was found. A comparison of the response of isomers of vitamin D3 by the HPLC method vs. other instrumental and chemical procedures shows HPLC to be the most specific method for determining the bioactive isomers.  相似文献   

8.
A method for the determination of vitamins D2 + D3 in fortified milk is described. Vitamins D2 and D3 are extracted from the saponified sample and converted to isotachysterols with antimony trichloride. The isotachysterols are quantitated using liquid chromatography with ultraviolet detection at 301 nm, which is the absorption maximum. At this wavelength other materials present in the sample do not interfere with the analysis of isotachysterols and therefore a cleanup step is avoided. Recoveries of vitamin D added to skim milk were 98.1% (SD 5.3), 96.7% (SD 3.3), and 96.0% (SD 5.1) for samples fortified with 200, 400, and 600 IU/quart, respectively. For whole milk, recoveries were 102.0% (SD 6.5) and 97.1% (SD 3.5) in samples fortified with vitamin D equivalent to 200 and 400 IU/quart, respectively. The detection limit for vitamin D is 40 IU/quart.  相似文献   

9.
A liquid chromatographic (LC) method was developed for determining vitamins D2 and D3 in fortified milk and infant formulas. The lipid-soluble components were extracted from the aqueous phase by homogenizing in isopropanol-methylene chloride with magnesium sulfate added to remove water. The vitamins were fractionated from the lipid material by using gel permeation chromatography (GPC) followed by further cleanup of the combined GPC fractions on a muBondapak/NH2 column. Four muStyragel (100 A) columns connected in series were used for GPC fractionation of sample extracts in methylene chloride. Injection and collection were repeated 3 times to collect enough vitamin D for quantitation. The muBondapak/NH2 column, using a mobile phase of methylene chloride-isooctane-isopropanol (600 + 400 + 1), resolved vitamin D from other UV-absorbing compounds and soy sterols in infant formula and from cholesterol in milk. Vitamins D2 and D3 coeluted as one peak, with the resolution and vitamin level sufficient for visual monitoring (280 nm/0.02 absorbance unit full scale) in a collection time of 22-26 min. A Zorbax ODS (6 micron) column and a methylene chloride-acetonitrile-methanol (300 + 700 + 2) mobile phase were used for LC quantitation; vitamins D2 and D3 were baseline resolved in about 11 min. The infant formula samples included ready-to-use and concentrated liquids prepared in nonfat milk base or soy base fortified with vitamins D2 or D3 at 400 IU/qt or L (10 micrograms). The mean percent recovery of added vitamin D3 (400-500 IU/qt) from infant formula (n = 7) was 89.6 +/- 6.7 (coefficient of variation (CV) 7.5%).(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

10.
A method is described for the determination of vitamin D3 in a liquid multivitamin preparation by liquid chromatography. Samples are purified on a disposable reverse phase extraction (SPE) column with a mobile phase of methanol-2-propanol (97 + 3) and are analyzed on a Zorbax ODS (5 micron) column with an acetonitrile-2-propanol-water (90 + 8 + 2) solvent system. Vitamin D3 is completely resolved from other interfering compounds within approximately 21 min and is detected with a UV detector at 254 nm. A mean of 98.5% of theory with a coefficient of variation of 3.8% was found for determination of vitamin D3 in a commercial preparation.  相似文献   

11.
A collaborative study was carried out which compared the official chemical method, 43.B14-43.B24, the official rat bioassay, 43.165, and the high pressure liquid chromatographic method for vitamin D3 resin, vitamin D3 resin in oil, and dry concentrate. A total of 340 samples were distributed to 17 collaborators for analysis. Five laboratories performed both the chemical and HPLC methods on 5 sets of blind duplicates. A 2-way analysis of variance comparing both methods for each sample showed a significant (P less than 0.01) difference between methods only for Sample 5. When the 2 methods were compared over all the samples, no significant (P less than 0.05) difference was found. Except for Sample 5, there were no differences in the repeatability of the methods. Per cent recoveries on Sample 3, which contained exactly 0.200 X 10(6) IU/g, showed 98.2% for the chemical method and 100.6% for the HPLC method for the 5 laboratories that performed both methods. The assay results of the HPLC and chemical methods are in good agreement with those found by the biological assay on Samples 1-4, but not for Sample 5. Evidence indicates that Sample 5 degraded partially to isotachysterol, and while the HPLC method yielded a reasonable value on this material, the chemical method erroneously showed full potency. An amendment is included for the collaboratively studied HPLC method which detects and eliminates 5,6-trans-vitamin D3, a possible interferant.  相似文献   

12.
Vitamin A (vitamin A palmitate) and vitamin E (alpha-tocopheryl acetate) levels were determined in 77 samples of fortified infant formulas manufactured by 4 firms in the United States from 1981 to 1983 and were compared by formulation base (soy, milk) and manufacturing firm. For vitamin A and vitamin E, the mean values (IU/100 kcal) were 454 +/- 95 (range 248-614) and 2.0 +/- 0.7 (range 1.1-5.0), respectively. No significant differences (alpha = 0.05) were found in levels (IU/100 kcal) of vitamin A and vitamin E between milk- and soy-based formulas. When the mean vitamin A and vitamin E levels of formulas produced by the various firms were compared on an IU/100 kcal or percent of label declaration basis, significant differences (alpha = 0.05) were found among firms. Mean vitamin A levels for the various products compared to label declarations ranged from 126% of declared for the ready-to-use formulas to 139% of declared for the powders. Mean vitamin E levels ranged from 97% of declared for ready-to-use formulas to 118% of declared for concentrates. Except for one sample that contained 248 IU vitamin A/100 kcal, the formulas met the requirements of the 1980 Infant Formula Act.  相似文献   

13.
A collaborative study was carried out which compared the official chemical method (43.B14-43.B24), the HPLC method according to Hofsass et al. including maleic anhydride treatment, and the HLPC procedure according to De Vries et al. for vitamin D concentrates. A total of 396 samples were distributed to 33 collaborators for analysis. Five laboratories performed both the chemical and the HPLC methods. Five laboratories performed the Hofsass method and 16 laboratories performed the De Vries method. The results for the chemical method agreed with the theoretical values for the samples, and the standard deviation was comparable to that obtained in previous AOAC collaborative studies. Collaborative results for the Hofsass method were low. In addition, incorrect use of a fixed conversion factor (1/0.586) and necessity of a double chromatogrpahic system on a non-treated and a treated vitamin D sample reduce the effectiveness of the method. There were no adverse reactions to the DE Vries HPLC method. It is recommended that the method be adopted official first action as an alternative procedure for determining vitamin D in concentrates, excluding powders containing irradiated 7-dehydrocholesterol.  相似文献   

14.
Effect of cholecalciferol-enriched hen feed on egg quality   总被引：1，自引：0，他引：1  
Eggs are one of the most important sources of vitamin D in the human diet, and their vitamin D content can be further increased by adding more vitamin D to hen feed. To investigate this issue more closely, we performed two feeding experiments. In both, zero egg samples were collected while the hens were fed regular feeds with a vitamin D content of 1720 or 4280 IU/kg. In experiment 1, egg samples were collected 2, 4, 7, 9, 11, 13, 16, 23, and 30 days after beginning the high-cholecalciferol (11 200 IU/kg) feeding period. In experiment 2, samples were collected 2, 4, 6, 8, 13, 28, 56, 84, 112, 140, and 168 days after beginning the high-cholecalciferol (12 000 IU/kg) diet. The egg samples were then assayed for their cholecalciferol content, and some samples, also for the presence of 25-hydroxycholecalciferol by an HPLC method. Further, the vitamin D-fortified eggs were compared with the controls by a sensory evaluation, by conducting fatty acid and functional analyses (emulsion capacity, gel forming capacity, foaming properties) and by measuring eggshell strength. Because vitamin D can be toxic in high doses, we also performed histopathological tests on the hens at the end of experiment 2. The top cholecalciferol contents in egg yolk (ca. 30 microg/100 g) were reached 8-13 days from starting the high-cholecalciferol diet. After 112 days feeding the cholecalciferol content gradually decreased to ca. 22 microg/100 g. When added to eggs as described above, vitamin D did not affect their sensory or functional properties or their fatty acid composition. Moreover, the cholecalciferol levels used in this study appeared not to affect eggshell strength or to be harmful for hens.  相似文献   

15.
A liquid chromatographic (LC) method is described for the determination of vitamin D3 in sheep plasma. Samples are extracted by one of 2 different methods, depending on the concentration of vitamin D3. The samples are purified by using either a Sep-Pak silica cartridge or a small alumina column, followed by additional cleanup on a Metalsorb LC column. Final analysis was carried out on a 5 micron C18 column using a radial compression separation system with an acetonitrile-methanol solvent system. Vitamin D3 was completely resolved from any interfering compounds in the plasma; total run time was less than 15 min, using a variable wavelength detector set at 264 nm. The method was successfully applied to samples at levels of 1-10 ng added vitamin D3 mL sheep plasma, with recoveries in the range 90-97%.  相似文献   

16.
An enzyme-linked immunosorbent assay (ELISA) screening test (CITE PROBE) was compared to liquid chromatography (LC) for the determination of aflatoxins in naturally contaminated corn samples. The CITE PROBE, with a positive/negative cutoff of 5 ng/g aflatoxin B1, was correct (based on LC results) on 47 of 51 samples. Two of the incorrect responses by the CITE PROBE were false positives on samples containing 4.4 ng/g and 4.1 ng/g aflatoxins by LC. Another incorrect response was a false negative on a sample containing 5.5 ng/g aflatoxins by LC. The fourth incorrect response was a false positive on a sample containing 1.9 ng/g aflatoxins by LC. On the basis of these results, the CITE PROBE was determined to be a reliable screening method for the detection of greater than or equal to 5 ng/g aflatoxins in corn.  相似文献   

17.
The normal phase liquid chromatographic (LC) method for determination of trans- and cis-isomers of vitamin K1 (phylloquinone) in infant formula described here uses an Apex silica column, isocratic elution, and UV absorption detection at 254 nm. Vitamin K1 is extracted quantitatively from the product matrix by pretreating the as-fed liquid with concentrated ammonium hydroxide and methanol, and then extracting it with a 2:1 mixture of dichloromethane and isooctane. The extract is cleaned up by silica open-column chromatography and concentrated for LC analysis. For trans-vitamin K1, the method precision is less than or equal to 3.3% RSD (relative standard deviation), and the spike recovery is 98 +/- 4%. For cis-vitamin K1, the precision is less than or equal to 12% RSD, determined at levels near the detection limit, and the spike recovery is 95 +/- 9%. The detection limit is 0.3 ng for both isomers at signal/noise = 3.  相似文献   

18.
A liquid chromatographic (LC) method was compared with the AOAC mouse bioassay method (18.086-18.092) for determination of paralytic shellfish toxins in shellfish tissues. Shellfish samples were collected from Massachusetts coastal waters as part of a state surveillance program, and extracts of shellfish meat were analyzed for toxins by using both analytical methods. Overall correlation of the LC and bioassay methods is good (r = 0.943), but for samples with toxicities less than 100 micrograms saxitoxin/100 g shellfish meat, the correlation is significantly less (r = 0.531). Limits of detection are 10 micrograms saxitoxin/100 g shellfish meat and 40 micrograms saxitoxin/100 g shellfish meat for the LC and bioassay methods, respectively. Analytical capacity of the LC method is limited to 12 samples/person-day compared with 30 samples/person-day for the bioassay. Sampling capacity of the LC method could be increased by using a fluorescence detector with a wider response range, which would eliminate the need for dilution of concentrated samples.  相似文献   

19.
Vitamin D in different fortified foods is determined by using liquid chromatography (LC). Sample preparation is described for fortified skim milk, infant formulas, chocolate drink powder, and diet food. The procedure involves 2 main steps: saponification of the sample followed by extraction, and quantitation by LC analysis. Depending on the sample matrix, additional steps are necessary, i.e., enzymatic digestion for hydrolyzing the starch in the sample and cartridge purification before LC injection. An isocratic system consisting of 0.5% water in methanol (v/v) on two 5 microns ODS Hypersil, 12 X 0.4 cm id columns is used. Recovery of vitamin D added to unfortified skim milk is 98%. The results of vitamin D determination in homogenized skim milk, fortified milk powder, fortified milk powder with soybean, chocolate drink powder, and sports diet food are given.  相似文献   

20.
Three different methods were compared for the determination of total flatoxins in corn and peanuts naturally contaminated with aflatoxins and in corn, peanuts, cottonseed, peanut butter, and poultry feed spiked with aflatoxins B1, B2, and G1. The 3 methods were an enzyme-linked immunosorbent assay (ELISA) screening test; a monoclonal antibody-affinity column-solid-phase separation method; and the AOAC official thin-layer chromatography (TLC) methods for all except poultry feed, for which Shannon's TLC method for mixed feed was used. The ELISA test is designed to provide only positive results for total aflatoxins at greater than or equal to 20 ng/g or negative results at less than 20 ng/g. The affinity column separation is coupled with either bromination solution fluorometry to estimate total aflatoxins or liquid chromatography (LC) to quantitate individual aflatoxins. Fluorodensitometry was used to determine aflatoxins in commodities analyzed by the TLC methods. The LC and TLC results were in good agreement for all the analyses. The results for the affinity column using bromination solution fluorometry were similar except those for cottonseed, which were about 60% higher. The ELISA screening method correctly identified naturally contaminated corn and peanut positive samples. No false positives were found for controls. The correct response for spiked corn, raw peanuts, peanut butter, and cottonseed at greater than or equal to 20 ng aflatoxins/g was about 90%. The correct response for spiked poultry feed at greater than or equal to 20 ng aflatoxins/g was about 50%.  相似文献   

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