Showing papers in "Journal of AOAC International in 1979"

Intercomparison study on the determination of single administration toxicity in rats.

Abstract: In 1977, the Commission of the European Communities initiated an intercomparison study to determine the single administration oral LD50 value in rats of each of 5 chemicals with the aims of comparing experimentation technologies, determining the degree of variation in the results and the various parameters used to establish the LD50 value, and establishing a common protocol for the determination of the LD50 value. Sixty-five laboratories in 8 countries took part in the first study. The significant variation in protocol may have led to the large interlaboratory variation observed in the results. Therefore, participating laboratories carried out a second study using a common protocol, preceded by a pilot study. A total of 100 laboratories in 13 countries participated. A majority of results of the second study are currently being analyzed, and the indications are that the interlaboratory variation has been significantly reduced.

High pressure liquid chromatographic determination of carbohydrates in food products: evaluation of method.

Abstract: A high pressure liquid chromatographic (HPLC) method for determining 5 common carbohydrates in food products was evaluated. Reproducibility data were generated showing a relative standard deviation of 2.8%. Recovery studies on a variety of foods gave an average recovery of 98.8%. The HPLC data for 3 varieties of ready-to-eat cereals were compared with data from 4 independent laboratories using current AOAC chemical methods. The HPLC mean values differed from the chemical mean values by 3.2%.

High pressure liquid chromatographic determination of vitamins A and E in cereal products.

Abstract: A rapid method for the simultaneous determination of vitamins A and E in fortified cereal products has been developed Saponification of retinyl or tocopheryl esters is not required, permitting direct injection of the extracted lipids onto the high pressure liquid chromatographic column without sample cleanup Elution times of 246 and 340 min were determined for retinyl palmitate and tocopheryl acetate, respectively, using a muPorasil column and an isocratic mobile phase of hexane-chloroform (85 + 15) with a flow rate of 15 mL/min The average recovery of retinyl palmitate was 992% (std dev 428), and the average recovery of tocopheryl acetate was 949% (std dev 410) in 2 cereals containing corn, oat, rice, and wheat No significant amounts of naturally occurring tocopherols were found in the cereals

Colorimetric determination of uric acid in poultry excreta and in mixed feeds.

Abstract: Uric acid was determined in samples of poultry excreta and animal feeds to which poultry excreta were added. The rapid colorimetric method used by Van Handel was adapted for this purpose. The method is simple, accurate, and gives reproducible results.

Survey of some market basket commodities for polynuclear aromatic hydrocarbon content.

Abstract: The Food and Drug Administration multi-component regulatory procedure for determining polynuclear aromatic hydrocarbons in foods was recently used to survey 24 foodstuffs for the presence of these compounds. The procedure has a reliable limit of quantitation of 2 ppb. The potent carcinogen benzo(a)pyrene was detected in only one of the 24 products analyzed, at a level of 3 ppb. Pyrene and/or fluoranthene were found in 19 of the 24 samples examined, at levels ranging from less than 1 ppb to about 75 ppb. A comparison of the recent survey data to that obtained approximately 10 years ago reveals that the types and levels of polynuclear aromatic hydrocarbons found are essentially unchanged.

Some principles of microbiological turbidimetric assays of antibiotics.

Abstract: Turbidimetric methods for determining the potency of antibiotics are inherently more accurate and more precise than are comparable agar diffusion procedures, but assays conducted in liquid media are subject to degradation from less than ideal conditions to a much greater extent than are diffusion methods. The relationships between test organisms, antibiotics, and assay concentrations are discussed. A valid assay procedure must produce a linear response with an adequate slope (-0.4 to -1.2) by the test organism to increasing concentrations of drug; such linear response normally occurs over a limited range of concentrations. Criteria used to select photometers that offer the greatest advantages to analytical microbiologists are described, with guidelines for the most effective use of the chosen instrument.

Gas-liquid chromatographic determination of bromide ion in lettuce: interlaboratory studies.

Abstract: The gas-liquid chromatographic method for the determination of bromide ion, as originally described for grain by Heuser and Scudamore, was adapted for use on lettuce, and later on products of other vegetable or of animal origin. After optimization of the ashing and derivatization conditions, 2 interlaboratory studies were carried out in The Netherlands. In the first, a preparatory study, 6 laboratories investigated freeze-dried lettuce; in the second definitive study, 8 laboratories investigated both freeze-dried and fresh lettuce. Four lots of lettuce with bromide contents ranging from about 5 to about 200 mg/kg were investigated. Average bromide contents (mg/kg) and between-laboratory coefficients of variation were 5.6 (11.0%), 13.3 (18.4%), 29.9 (8.3%), and 209 (12.8%). The results obtained are normal for the type of work and the conditions of the study. The method will be recommended for regulatory use in The Netherlands and in international organizations.

Gas-liquid chromatographic determination of individual sugars in confectionery products.

Abstract: A gas-liquid chromatographic (GLC) procedure is presented for the separation and quantitative determination of sucrose, lactose, maltose, and glucose in commercial confectionery products. By converting reducing sugars to oximes and then forming trimethylsilyl ethers of these compounds and separating them on a 6 ft X 4 mm id glass column packed with 2% OV-17 on 100--120 mesh Supelcoport, single peaks were obtained for each of the sugars. Results for sugars present in samples at levels of 5% or more are within 2.8%, on the average, of results obtained by polarization measurements. The data also compare favorably with others in the literature on similar products analyzed by other GLC procedures that do not involve oxime formation.

DC polarography of cephradine and its application to capsules.

Abstract: A polarographic method has been developed for the quantitative analysis of cephradine and its dosage forms. Direct determinations on capsules are carried out; excipients and coloring matter do not interfere in the determination. The electroactive product is formed by acidic hydrolysis with 5.0N HCl and heating at 80 degrees C for 60 min. Two polarographic waves are obtained: I = -0.46 V and II = -0.78 v vs. SCE. Both reduction waves are diffusion controlled. Wave I is preferred for analytical purposes. The precise chemical identity of the electroactive product has not been determined, but UV spectral data and the TLC Rf value are reported. A linear relation is established for levels of cephradine between 10(-2) and 10(-5)M in 5.0N HCl.

Comparison of studies on saccharin and sodium nitrite.

Abstract: A review of long term animal studies of saccharin and sodium nitrite was undertaken to assess the effect of variability of selected protocol elements on the results obtained. These elements were divided into 4 general categories: design, including selection of test animals, basal diet, dosage form and doses of test substance, route of administration, and duration of exposure; observations, including gross observations during life and at necropsy, clinical tests, and histopathology; performance, including conduct of the test and animal husbandry; and analytical procedures, including chemical and statistical analyses. Because many of the protocol elements are not fully discussed in study reports, it was often impossible to determine what actually had been done. The review of various saccharin studies suggests that bladder tumors resulted following in utero exposure. In utero exposure with sodium nitrite did not appear to cause reticuloendothelial changes. The numerous variations in protocol elements in the nitrite studies precluded identification of a prime element responsible for the variation in reticuloendothelial changes observed. It can be concluded from this review that achievement of reproducibility in long term studies requires minimal variation of protocol elements for the new study.

High pressure liquid chromatographic determination of naphthaleneacetic acid residues in apples.

Abstract: An ion-suppression reverse phase high pressure liquid chromatographic method is described for determining naphthaleneacetic acid (NAA) residues in apples. Samples are extracted with acidic chloroform, filtered through pre-acidified Hy-Flo Supercel, and cleaned up by acid-base partitioning. The extract can be successfully chromatographed on either a muLiChrosorb NH2 or muBondapak C18 column and quantitated by using a variable wavelength ultraviolet detector set at 220 nm. The mobile phase is acetonitrile-water (20 + 80) buffered to pH 3.5 (MULiChrosorb column) or pH 5.2 (MUBondapak column) and flowing at 1.0--2.0 ml/min. Recoveries ranged from 86 to 98%. The minimum detectable amount was 0.5 ng, which easily permitted the quantitation of 0.01 ppm NAA in 50 g sample. A fluorometric detector was 4 times as sensitive, using an excitation wavelength of 220 mm and monitoring the emission at 340 nm. For this detector, the minimum detectable amount was 0.12 ng NAA.