AOAC Official Method 942.05, Ash in Animal Feed, has been applied in feed laboratories since its publication in the Official Methods of Analysis in 1942. It is a routine test with renewed interest due to the incorporation of "ash values" into modern equations for the estimation of energy content of dairy feed, beef feed, and pet food. As with other empirical methods, results obtained are a function of the test conditions. For this method, the critical conditions are the ignition time, ignition temperature, and any other furnace or weighing conditions. Complete ignition can be observed by the absence of black color (due to residual carbonaceous material) in the ash residue. To investigate performance of AOAC 942.05, 15 samples were chosen to be representative of a wide range of feed materials. These materials were tested at the conditions of AOAC 942.05 (ignition at 600 degrees C for 2 h) and similar or more rigorous conditions. The additional conditions investigated included: 600 degrees C for 4 h; 600 degrees C for 2 h, cool, and ignite 2 additional h; 600 degrees C for 2 h, cool, wet, dry, and ignite 2 additional h; 550 degrees C for 6 h; 550 degrees C for 3 h, cool, and ignite 3 additional h; and 550 degrees C for 3 h, cool, wet, dry, ignite 3 additional h. Results for all other conditions investigated were found to be significantly different from the current AOAC Method 942.05. All ignition conditions were significantly different from each other except two: 550 degrees C for 3 h, cool, ignite 3 additional h; and 550 degrees C for 3 h, cool, wet, dry, and ignite 3 additional h. Recommendations for modification to AOAC Official Method 942.05 are suggested based on statistical analysis of the data and a review of the literature.
: Because of its chemical complexity, the estimation of dietary fiber content of feed and food materials is a difficult analytical challenge. Three major fiber analyses are conducted routinely in the United States including crude fiber (CF), detergent fiber, and total dietary fiber (TDF). : Factors crucial to the successful measurement of dietary fibers are described and suggestions provided as to how to overcome potential analytical problems within assays.: An accounting of methodological details that result in variation in fiber concentration values is presented along with suggestions as to how to decrease the variation. : CF analysis remains in use in the livestock feed and pet food industries for nutrition labeling purposes in spite of the fact that the analysis does not separate mammalian enzyme-digestible from indigestible carbohydrate components, and values obtained are usually 30-50% of the actual dietary fiber concentration. Detergent fiber methods quantify the insoluble dietary fibers (IDF) accurately, but not the soluble dietary fiber (SDF) components. TDF methods account for intrinsic and intact fibers, isolated and extracted fibers, and synthetic fibers found in feed and food ingredients and complete diet matrixes.: The CF procedure should be abandoned as it fails to quantify fiber properly. Detergent analyses quantify IDF. TDF methods quantify both IDF and SDF. : Accurate dietary fiber quantification is essential given the role of fiber in health and well-being of animals and humans.
Background Vitamin A test results have historically been notorious for poor repeatability and reproducibility. This problem has been discussed at length in Association of American Feed Control Officials Laboratory Methods and Services Committee meetings. Objective The objective of this work was to assess the effect of test portion mass on the repeatability of vitamin A test results. Methods The study was conducted in two parts. In Part 1, fundamental sampling error was determined experimentally through replicated (n = 16) vitamin A testing of three animal feed materials. The testing followed rigorous test portion selection for 10 g and 100 g test portions. In Part 2, fundamental sampling error calculations were made 1) using theoretical equations based on vitamin A as a liberated analyte and 2) on representing the particles in feed materials. Particle size characterization of vitamin A ingredients was estimated by microscopy and further evaluated by particle size analysis. Results Relative standard deviations (RSDs) for vitamin A determinations ranged from 10.5–24.7%, and 2.3–10.7% for 10 g and 100 g test portions, respectively. Fundamental sampling error calculated for Ingredient A ranged from 18.2–98.9% and 5.8–31.2% for 10 g and 100 g test portions, respectively, and for Ingredient B, ranged from 10.1–54.9% and 3.2–17.4% for 10 g and 100 g test portions, respectively. Conclusions Test portion mass has a substantial impact on fundamental sampling error and is an important factor in controlling the random error in vitamin A testing. Fundamental sampling error equations are useful to approximate minimum test portion mass. Highlights Vitamin A method development should use theoretical predictions and experimental verification to guide test portion mass. Strategies to deal with the larger test portion masses will be key to validating new methods.
The concentration of oxygen in the primary β-phase of Zr-1%Nb alloy was investigated using SIMS and thermal evolution analysis (TEA). The specimens were as-received or preoxidized in water vapor (425 • C/10,7 MPa) to simulate the reactor conditions. Then the specimens were exposed to hot water vapor (0,1 MPa) and high temperatures (950-1200• C) for variable time intervals, which simulated the Loss of Coolant Accident (LOCA). The specimens were quenched in water with ice. Both SIMS and TEA quantitative results were in good agreement and were correlated with the mechanical properties (microhardness, residual ductility), which depend on the oxygen concentration and are important for the safety analyses assessment. The ceiling concentration of oxygen in the β-phase was established based on the experimental results of SIMS and TEA.
To improve throughput during peak seasonal demand, a screening method for the determination of fertilizer-available phosphate using a discrete analyzer for semi-automation was validated in a single laboratory. The fertilizer materials were extracted using a neutral EDTA-ammonium citrate solution as detailed in AOAC Official Method 993.31. Phosphate was subsequently freed from the matrix and converted to orthophosphate using an alkaline persulfate digestion modified from a U.S. Geological Survey water method. Phosphorus was determined colorimetrically on a discrete analyzer. Twelve check samples from the Magruder Fertilizer Check Sample Program and Association of Fertilizer and Phosphate Chemists Fertilizer Check Program were used for method validation experiments. The proposed method is linear from 0.01 to 20 mg/L (ppm) phosphorus. Recovery for all materials averaged 101%, with a range of 99.2 to 103%. Bias for all materials averaged 0.59% with a range of -0.11 to 1.68%, with bias increasing at concentrations of available phosphate exceeding 40%. The LOD was calculated to be 0.001% available phosphate and the LOQ 0.002% available phosphate. The method was found fit for purpose as a screening method for available phosphate analysis in fertilizers.
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