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.

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.

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.

Collaborative Study of a Method for Determination of Monosodium Glutamate in Food Products

1969 ◽  
Vol 52 (6) ◽  
pp. 1131-1132
Author(s):  
E Fernandez-Flores ◽  
Arthur R Johnson ◽  
Victor H Blomquist
Keyword(s):  
Standard Deviation ◽  
Glutamic Acid ◽  
Monosodium Glutamate ◽  
Collaborative Study ◽  
Food Products ◽  
Average Recovery

Abstract A method was collaboratively studied for the determination of monosodium glutamate as glutamic acid in food products. Six samples were submitted to each of nine collaborators. The quantity of monosodium glutamate in the samples ranged from 0.3 to 10%. The average recovery was 101.9% with a standard deviation of 3.6%. The method is recommended for adoption as official first action.

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.

High Pressure Liquid Chromatographic Determination of Bacitracin in Premix Feeds and Finished Feeds: Collaborative Study

1982 ◽  
Vol 65 (5) ◽  
pp. 1178-1185 ◽  
Author(s):  
John B Gallagher ◽  
Paul W Love ◽  
Linda L Knotts ◽  
◽  
M Allred ◽  
...  
Keyword(s):  
Standard Deviation ◽  
Collaborative Study ◽  
Chromatographic Determination ◽  
Chromatographic Technique ◽  
Reverse Phase ◽  
High Pressure Liquid Chromatographic ◽  
Repeatability Standard Deviation ◽  
Liquid Chromatographic Determination ◽  
Liquid Chromatographic

Abstract A liquid chromatographic technique for the determination of bacitracin in finished feeds and premix feeds consists of an isocratic reverse phase, ion-suppressed technique. The chromatography can be completed in less than 25 min. In a collaborative study involving 9 laboratories and 3 samples of bacitracin methylene disalicylic acid and 3 samples of bacitracin zinc premixes covering the range of 10-50 g/lb, the repeatability standard deviation was 0.55, and the reproducibility standard deviation was 1.35. The average recovery of the bacitracin was 102.0%. The method has been adopted official first action for bacitracin in premix feeds.

scholarly journals Determination of Selenium in Feeds and Premixes: Collaborative Study

1997 ◽  
Vol 80 (3) ◽  
pp. 469-480 ◽  
Author(s):  
Ivan S Palmer ◽  
Nancy Thiex ◽  
R Allen ◽  
E Alley ◽  
N Anderson ◽  
...  
Keyword(s):  
Statistical Analysis ◽  
Standard Deviation ◽  
Atomic Absorption ◽  
Collaborative Study ◽  
Hydride Generation ◽  
Poor Agreement ◽  
Reproducibility Standard Deviation ◽  
Repeatability Standard Deviation ◽  
Fluorometric Study

Abstract A total of 17 laboratories participated in a collaborative study for the determination of selenium in feeds and premixes using either a fluorometric or a continuous hydride generation atomic absorption (HGAA) method. Each collaborator analyzed 16 blind duplicate samples of feed and premixes from various feed manufacturers. The amount of Se in these materials ranged from 0.2 to 5500 μg/g. Six laboratories used only the fluorometric procedure, 8 laboratories used only the hydride generation atomic absorption procedure, and 3 laboratories used both procedures. One laboratory in the fluorometric study and 3 laboratories in the HGAA study were initially excluded because of invalid data. Poor agreement between the blind duplicates indicated probable sample interchange and/or dilution error. The data from 8 laboratories were submitted to statistical analysis, including data from 2 laboratories participating in both studies. The repeatability standard deviation (RSDr) for samples analyzed by the fluorometric procedure ranged from 5.9 to 33%, and the reproducibility standard deviation (RSDR) ranged from 12 to 33%. RSDf for samples analyzed by HGAA ranged from 2.8 to 18%, and RSDR ranged from 4.0 to 36%. Both fluorometric and continuous hydride generation atomic absorption methods for the determination of Se in feeds and premixes have been adopted first action by AOAC INTERNATIONAL.

Collaborative Study and Ion Exchange Method for the Determination of Methyldopa, Chlorothiazide, and Hydrochlorothiazide in Drug Mixtures

1971 ◽  
Vol 54 (3) ◽  
pp. 603-608
Author(s):  
Rod Chu
Keyword(s):  
Standard Deviation ◽  
Ion Exchange ◽  
Exchange Resin ◽  
Collaborative Study ◽  
Cation Exchange Resin ◽  
Resin Column ◽  
Exchange Method ◽  
Average Recovery ◽  
Ion Exchange Method

Abstract A method for the assay of methyldopa with either chlorothiazide or hydrochlorothiazide was studied collaboratively by 8 laboratories. The method involves the use of AG50-4X, 100-200 mesh H+ cation exchange resin to resolve the compounds. The thiazides pass freely through the resin column, while methyldopa is retained and subsequently eluted with 1N methanolic HCl. The components are quantitatively measured by spectrophotometry at 280 (methyldopa), 277 (chlorothiazide), and 270 nm (hydrochlorothiazide). For the methyldopa-chlorothiazide combination, the overall average recovery for methyldopa was 98.5% with a standard deviation of 2.50; and for the methyldopa-hydrochlorothiazide combination, 96.4% with a standard deviation of 2.30. The average recoveries for chlorothiazide and hydrochlorothiazide were 99.6 (standard deviation of 1.14) and 98.8% (standard deviation of 2.92), respectively. The method has been adopted as official first action for the determination of methyldopa and chlorothiazide in combination.

Determination of Nitrogen in Fertilizer by Combustion: Collaborative Study

1994 ◽  
Vol 77 (4) ◽  
pp. 829-839 ◽  
Author(s):  
Donald F Tate
Keyword(s):  
Standard Deviation ◽  
Ammonium Nitrate ◽  
Copper Catalyst ◽  
Collaborative Study ◽  
Combustion Method ◽  
Method Performance ◽  
Different Types ◽  
Kjeldahl Method ◽  
Repeatability Standard Deviation

Abstract Fourteen laboratories participated in a collaborative study to compare abilities of AOAC modified copper catalyst Kjeldahl method, 978.02, and the generic combustion method, 990.03, to analyze the nitrogen content of fertilizer materials. Combustion analyses are more time efficient, more accurate, and less hazardous than Kjeldahl analyses. There were 3 different types of instrumentation involved in the collaborative study: (1) Leco FP-428 Nitrogen Determinator; (2) Perkin-Elmer 2410 Series II Nitrogen Analyzer; (3) Carlo-Erba 1500 Series II Nitrogen Analyzer. Thirty samples of fertilizer containing 1–67% N included 2 ACS grade standard materials: ammonium nitrate, theory 35.00% N; and dicyandiamide, theory 66.64% N. A diammonium phosphate and urea mixture (3 + 1 ; 1.0 mm grind) and 2 ACS grade standard materials of ammonium nitrate and ammonium sulfate were supplied for repetitive combustion analyses. Overall method performance of the combustion method was at least as good as the modified Kjeldahl method. Repeatability standard deviation (Sr) values for the combustion method ranged from 0.09 to 0.34 vs the modified Kjeldahl method range of 0.06–0.49; reproducibility standard deviation (SR) values for the combustion method ranged from 0.13 to 1.07 vs the range of 0.09–3.57 for the modified Kjeldahl method. The grand mean was 20.78% for the combustion method, and 20.79% for the modified Kjeldahl method using various fertilizers. The average ranges of sr and SR for the methods were, respectively, 0.17 and 0.29 for the combustion method, and 0.19 and 0.54 for the modified Kjeldahl method. The method was adopted first action by AOAC INTERNATIONAL.

Cylinder Plate Assay for Determining Bacitracin in Premix Feeds and Finished Feeds: Collaborative Study

1982 ◽  
Vol 65 (5) ◽  
pp. 1168-1177
Author(s):  
John B Gallagher ◽  
Linda L Knotts ◽  
◽  
D Brennecke ◽  
H H Bryant ◽  
...  
Keyword(s):  
Standard Deviation ◽  
Collaborative Study ◽  
Reverse Phase ◽  
Average Recovery ◽  
Plate Assay ◽  
The Poor ◽  
Reproducibility Standard Deviation ◽  
Assay Procedure ◽  
Acceptable Method ◽  
Repeatability Standard Deviation

Abstract A cylinder plate assay procedure was studied by 10 laboratories. For premix feeds, 3 samples of bacitracin methylene disalicylic acid and 3 samples of bacitracin zinc premixes covering the range of 10 to 50 g/lb were used. The repeatability standard deviation was 2.11, and the reproducibility standard deviation was 2.13. The average recovery of bacitracin was 101.5%. The method has been adopted official first action. For finished feeds, 6 samples of bacitracin methylene disalicylic acid and 6 samples of bacitracin zinc covering the range of 10 to 800 g/ton were used in the study. The procedure included a sample cleanup step using disposable reverse phase columns. This step appears to be the cause of the poor results reported by most collaborators. Continued study is needed to develop an acceptable method for finished feeds.

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