Evaluation of the Babcock Method for the Determination of Milk Fat

1975 ◽  
Vol 58 (5) ◽  
pp. 949-956
Author(s):  
Myron R Mckinley ◽  
Richard E Arnold ◽  
John B Rosenbury ◽  
Earl C Born ◽  
Chapman E Dunham ◽  
...  
Keyword(s):  
Sulfuric Acid ◽  
Standard Deviation ◽  
Milk Fat ◽  
Collaborative Study ◽  
Tempering Temperature ◽  
Coefficients Of Variation ◽  
Sample Composition ◽  
Significant Difference ◽  
Repeatability Standard Deviation ◽  
Milk Solids

Abstract The Babcock test for fat in milk was evaluated to study the effects of variables such as glassware calibration, sample preparation, sample composition, reagents, tempering conditions, procedural variations, and analyst. Certain test bottles yielded significantly different results; however, there was little indication of pipet variation. Analysis of the various techniques for tempering and mixing indicated that samples tempered at 68°F (20°C), containing an airspace of approximately 25% of the total container, and mixed by inversion 5–10 times or poured from one container to another gave the most consistent results. Sample composition did not affect results, provided all milk-solids-notfat were digested by the sulfuric acid. A pipet draining time of 10 sec followed by blowing out the pipet was sufficient to yield reproducible results. Differences between lots of sulfuric acid affected results. Results were 0.027% less when the final test tempering was 130°F (54.5°C) compared to 140°F (60°C); however, a final tempering for a minimum of 3 min gave satisfactory results. Variations in reading results between individual analysts were negligible. The Babcock method for fat in milk, modified to include the optimum parameters as determined in this study, was subjected to a collaborative study. Nine laboratories analyzed 10 samples in duplicate. Statistical analysis of collaborative data indicates a significant difference between laboratories (p <0.01 ). The repeatability standard deviation of the method is 0.0183%. The reproducibility standard deviation is 0.0407%. The repeatability and reproducibility coefficients of variation are 0.53 and 1.17%, respectively. On the basis of the collaborative results, the following changes have been incorporated into the official final action method: specifications for the reading light; sample draining time; tempering temperature of the acid; tempering procedure for reading the test bottle.

Microdiffusion and Fluoride-Specific Electrode Determination of Fluoride in Infant Foods: Collaborative Study

1981 ◽  
Vol 64 (4) ◽  
pp. 1021-1026
Author(s):  
Robert W Dabeka ◽  
Arthur D Mckenzie ◽  
◽  
R A Baetz ◽  
D W Bingham ◽  
...  
Keyword(s):  
Standard Deviation ◽  
Collaborative Study ◽  
Variance Analysis ◽  
Infant Foods ◽  
Reproducibility Standard Deviation ◽  
Coefficients Of Variation ◽  
Repeatability Standard Deviation

Abstract Twelve laboratories analyzed (1 replicate) 12 samples of infant foods – milk, pears, and peas – containing 0.2-5 ppm F. There was one laboratory outlier. Mean coefficients of variation were 7.06% for intralaboratory determination of 3 sets of blind duplicates and 21.6% for interlaboratory determination of 12 samples. Variance analysis for all samples yielded a reproducibility standard deviation of 0.41 ppm; for 3 sets of blind duplicates, repeatability standard deviation was 0.26 ppm and reproducibility standard deviation was 0.32 ppm.

Sulfuric Acid/Hydrogen Peroxide Digestion and Colorimetric Determination of Phosphorus in Meat and Meat Products: Collaborative Study

1991 ◽  
Vol 74 (1) ◽  
pp. 22-26 ◽  
Author(s):  
David K Christians ◽  
Thomas G Aspelund ◽  
Scott V Brayton ◽  
Larry L Roberts
Keyword(s):  
Hydrogen Peroxide ◽  
Sulfuric Acid ◽  
Collaborative Study ◽  
Meat Products ◽  
Colorimetric Determination ◽  
Pork Sausage ◽  
Relative Standard ◽  
Significant Difference ◽  
Standard Deviations

Abstract Seven laboratories participated In a collaborative study of a method for determination of phosphorus in meat and meat products. Samples are digested In sulfuric acid and hydrogen peroxide; digestion Is complete In approximately 10 mln. Phosphorus Is determined by colorimetric analysis of a dilute aliquot of the sample digest. The collaborators analyzed 3 sets of blind duplicate samples from each of 6 classes of meat (U.S. Department of Agriculture classifications): smoked ham, water-added ham, canned ham, pork sausage, cooked sausage, and hamburger. The calibration curve was linear over the range of standard solutions prepared (phosphorus levels from 0.05 to 1.00%); levels in the collaborative study samples ranged from 0.10 to 0.30%. Standard deviations for repeatability (sr) and reproducibility (sR) ranged from 0.004 to 0.012 and 0.007 to 0.014, respectively. Corresponding relative standard deviations (RSDr and RSDR, respectively) ranged from 1.70 to 7.28% and 3.50 to 9.87%. Six laboratories analyzed samples by both the proposed method and AOAC method 24.016 (14th Ed.). One laboratory reported results by the proposed method only. Statistical evaluations Indicated no significant difference between the 2 methods. The method has been adopted official first action by AOAC.

Colorimetric Method for Carbadox in Feeds: Collaborative Study

1977 ◽  
Vol 60 (5) ◽  
pp. 1059-1063
Author(s):  
John T Goras
Keyword(s):  
Standard Deviation ◽  
Stannous Chloride ◽  
Collaborative Study ◽  
Colorimetric Method ◽  
Feed Supplement ◽  
Colored Complex ◽  
Feed Supplements ◽  
Repeatability Standard Deviation ◽  
Standard Additions ◽  
The Mean

Abstract A colorimetric method for determining carbadox in complete swine feeds and feed supplements was collaboratively studied. Carbadox is separated from feed with CHCl3-methanol (3+1) and then separated from interfering materials by a series of solvent-solvent extractions. The drug is isolated as a dry residue, reconstituted, and reacted with stannous chloride to form a colored complex that is measured at 520 nm. The method of standard additions is used to compensate for a feed or feed supplement matrix effect. Twenty-seven laboratories assayed feeds containing 0.0013, 0.0053, and 0.0242% carbadox. The repeatability standard deviation (σ0) and reproducibility standard deviation (σx) were σ0 = 0.00014%, σx = 0.00035% (29% of grand mean) for 0.0013% carbadox in feed; σ0 = 0.00025%, σx = 0.00037% (6.7% of grand mean) for 0.0053% carbadox in feed; and σ0 = 0.0019%, σx = 0.0024% (9.6% of grand mean) for 0.0242% carbadox in feed. The between-laboratory variance ratio was not significant for feeds containing 0.0013 and 0.0053% carbadox, but was significant for feeds containing 0.0242% carbadox. The mean recovery values for feeds containing 0.0013, 0.0053, and 0.0242% carbadox were 92, 104, and 103%, respectively. The method was adopted as official first action for feeds having a guaranteed potency of 0.0055% carbadox or higher.

Experimental Designs for Interlaboratory Precision Experiments: Comparison of ISO 5725 with Draft NEN 6303

1989 ◽  
Vol 72 (1) ◽  
pp. 34-37 ◽  
Author(s):  
J Zaalberg
Keyword(s):  
Standard Deviation ◽  
Edible Oils ◽  
Collaborative Study ◽  
Experimental Designs ◽  
Interlaboratory Experiments ◽  
Interlaboratory Studies ◽  
Repeatability Standard Deviation ◽  
Level Design ◽  
Iso 5725

Abstract To determine the precision of standardized analytical methods, interlaboratory experiments are carried out in which several laboratories analyze identical samples from well homogenized batches of material. From the test results, estimates of the standard deviations under repeatability as well as under reproducibility conditions are calculated. In the present work, the experimental designs recommended in the International Standard ISO 5725 have been compared with a design proposed in the draft Netherlands Standard NEN 6303. This has been done by comparing their mathematical models as well as by applying them to the results of a recent collaborative study on the determination of heavy metals in edible oils and fats. The reproducibility standard deviation is estimated equally well with both Standards, but it appeared that the designs given in ISO 5725 can lead to serious underestimation (uniform-level design) or overestimation (split-level design) of the repeatability standard deviation. By using the design proposed in NEN 6303, these biases can be avoided. Hence, it is recommended that interlaboratory studies be organized according to the design of NEN 6303.

Modified Method for Carbadox in Feeds: Collaborative Study

1979 ◽  
Vol 62 (5) ◽  
pp. 982-984
Author(s):  
John T Goras
Keyword(s):  
Standard Deviation ◽  
Room Temperature ◽  
Collaborative Study ◽  
Variance Ratio ◽  
Modified Method ◽  
Repeatability Standard Deviation ◽  
Standard Solution ◽  
The Mean ◽  
Optimum Working ◽  
Statistical Results

Abstract The official first action method for carbadox in swine feed, 42.C01-42.C04, was modified in 2 respects. First, the samples were leached overnight at room temperature instead of boiled for 1 hr. This change avoided problems with overheating and excessive evaporation. Second, the dilution scheme for samples spiked with carbadox standard solution was changed to give absorbance values that were within the optimum working range of all types of spectrophotometers. The modified procedure was collaboratively studied by 21 laboratories. The repeatability standard deviation (σo) and reproducibility standard deviation (σo) were σ0 = 0.00029% and σx = 0.00056% (8.9% of grand mean) for feeds containing 0.00617% carbadox; and σo = 0.0012% and σx = 0.0019% (9.3% of grand mean) for feeds containing 0.0198% carbadox. The between-laboratory variance ratio was significant for feeds containing 0.0198% carbadox. The mean per cent of intent values for feeds containing 0.00617% carbadox and 0.0198% carbadox were 102% and 104%, respectively. In general, the statistical results were comparable to those previously obtained for the official first action method. Consequently, the modified procedure is not recommended as a replacement for the official first action method.

Collaborative Study of the Determination of Dichlorophene in Veterinary Preparations by Ultraviolet Spectrophotometry

1972 ◽  
Vol 55 (1) ◽  
pp. 163-165
Author(s):  
Dalia M Gilvydis
Keyword(s):  
Standard Deviation ◽  
Collaborative Study ◽  
Liquid Extraction ◽  
Synthetic Mixture ◽  
Ultraviolet Spectrophotometry ◽  
Average Recovery ◽  
Liquid Liquid Extraction ◽  
Coefficients Of Variation ◽  
Standard Deviations

Abstract Dichlorophene is determined in veterinary preparations by a liquid-liquid extraction and UV quantitation. Eight collaborators each analyzed 4 commercial preparations and one synthetic mixture. The average recovery for dichlorophene in the synthetic mixture is 100.3% with a standard deviation of 2.13. The standard deviations obtained for the 5 samples range from 0.13 to 3.69 with coefficients of variation from 0.69 to 3.43. It is recommended that the method be adopted as official first action.

Mass Loss on Drying for Instant Coffee: Collaborative Study

1980 ◽  
Vol 63 (2) ◽  
pp. 178-179
Author(s):  
William P Clinton ◽  
Paul H Manni ◽  
John M Ferry
Keyword(s):  
Standard Deviation ◽  
Mass Loss ◽  
Coefficient Of Variation ◽  
Collaborative Study ◽  
Instant Coffee ◽  
Reproducibility Standard Deviation ◽  
Repeatability Standard Deviation ◽  
Working Method

Abstract A collaborative study was undertaken to define an acceptable routine working method for determination of mass loss in instant coffee. Fourteen laboratories of 24 invited to participate submitted results. The repeatability standard deviation and coefficient of variation were 0.026 and 0.7%, respectively. The reproducibility standard deviation and coefficient of variation were 0.153 and 3.8%, respectively. The method has been adopted as official first action.

Determination of Total Nitrogen in Urine by Pyrochemiluminescence: Collaborative Study

1995 ◽  
Vol 78 (2) ◽  
pp. 301-306 ◽  
Author(s):  
Kristi A Boehm ◽  
P Frank Ross
Keyword(s):  
Standard Deviation ◽  
Total Nitrogen ◽  
Collaborative Study ◽  
Urine Samples ◽  
External Control ◽  
Severe Stress ◽  
Average Recovery ◽  
Oxidative Pyrolysis ◽  
Repeatability Standard Deviation

Abstract Twelve collaborating laboratories analyzed 5 blind duplicate samples of human urine for total nitrogen using a pyrochemiluminescence method. The nitrogen content ranged from low (650 mg/L) to high levels (8800 mg/L) in urine samples of people under moderate to severe stress. In addition to test samples, collaborators also received a certified standard (sodium nitrite in water) as an external control. The pyrochemiluminescence assay was performed on urine samples diluted in water within a range of 1:50 to 1:100. The method detects total nitrogen by reaction of the product of high temperature oxidative pyrolysis and ozone. Repeatability standard deviation values (RDSr) ranged from 1.49 to 3.91% and reproducibility standard deviation values (RSDR) ranged from 3.66 to 9.57%. The average recovery of total nitrogen was 99.9%. The pyrochemiluminescence method for determination of total nitrogen in urine was adopted first action by AOAC INTERNATIONAL.

IUPAC Gas Chromatographic Method for Determination of Fatty Acid Composition: Collaborative Study

1979 ◽  
Vol 62 (4) ◽  
pp. 709-721
Author(s):  
David Firestone ◽  
William Horwitz
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Butyric Acid ◽  
Vegetable Oils ◽  
Milk Fat ◽  
Methyl Esters ◽  
Collaborative Study ◽  
Fats And Oils ◽  
Check Sample ◽  
Coefficients Of Variation

Abstract An international collaborative study of IUPAC methods II.D.19 and II.D.25 for preparation and GLC analysis of fatty acid methyl esters was begun in 1976. The IUPAC methodology, applicable to animal and vegetable oils and fats and fatty acids from all sources, contains special instructions for preparation and analysis of methyl esters of fatty acids containing 4 or more carbon atoms (analysis of milk fat). Twenty-three collaborators participated in the analysis of 5 known mixtures, 4 vegetable oils, 1 fish oil, and 2 butterfats. Several blind duplicate samples were included. The experimental data were subjected to statistical analysis to examine intra- and interlaboratory variation. Reproducibility and accuracy data for the higher fatty acid (14:0–22:1) mixtures and fish and vegetable oils were satisfactory and were in good agreement with results from an AOCS Smalley Committee check sample program involving analysis of the same samples. Typical coefficients of variation (%) at various concentrations were 15 (2% level), 8.5 (5% level), 7 (10% level), and 3 (50% level). Low recoveries and poor reproducibility were characteristic of results obtained for butyric acid in the butterfat and related known mixtures. A coefficient of variation of about 19% was found for analysis of butyric acid in butterfat, vs. coefficients of variation in the range of 4–13% for similar levels of other components in butterfat and other samples. The IUPAC methodology for GLC analysis .of fats and oils other than milk fats has been adopted by the AOAC as official first action to replace the current GLC method, 28.063-28.067.

Collaborative Study of a Colorimetric Determination of Nitrate in Tobacco

1969 ◽  
Vol 52 (4) ◽  
pp. 756-759
Author(s):  
C James Rosene
Keyword(s):  
Sulfuric Acid ◽  
Standard Deviation ◽  
Systematic Error ◽  
Collaborative Study ◽  
Colorimetric Method ◽  
Water Soluble ◽  
Colorimetric Determination ◽  
Error Standard Deviation

Abstract A colorimetric method for determining water-soluble nitrate in tobacco was studied by 14 laboratories on eight Burley and two cigar filler tobacco samples with nitrate levels of 0.5–2.4%. In the method, ground tobacco is extracted with water and filtered, and an aliquot is then treated with 2,4-xylenol in sulfuric acid; then the resulting 6-nitro-2,4-xylenol is removed by distillation and measured spectrophotometrically at 450 µm. Results show that, althoughthe precision standard deviation among laboratories is generally acceptable, the systematic error standard deviation is unacceptably high. This study will be continued.

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