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.

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.

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.

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.

Electrothermal Atomic Absorption Spectrometric Determination of Selenium in Foods and Diets

1983 ◽  
Vol 66 (5) ◽  
pp. 1129-1135 ◽  
Author(s):  
Jorma Kumpulainen ◽  
Anna-Maria Raittila ◽  
Jari Lehto ◽  
Pekka Koivistoinen
Keyword(s):  
Atomic Absorption ◽  
Collaborative Study ◽  
Hydride Generation ◽  
Bovine Liver ◽  
Pyrrolidine Dithiocarbamate ◽  
Matrix Modifier ◽  
Organic Extraction ◽  
The Mean ◽  
Atomic Absorption Spectrometric

Abstract The validity of 2 electrothermal atomic absorption spectrometric methods for determination of selenium in foods and diets was tested. By using 0.5% Ni(II) as a matrix modifier to prevent selenium losses during the ashing step, it was shown that selenium can be determined in samples containing ≥1 μg Se/g dry wt without organic extraction. The mean recovery tested, using NBS Bovine Liver, was 98%; recovery of added inorganic selenium in Bovine Liver matrix was 100%. In addition, this method gave values closest to the median value of all participating laboratories using hydride generation AAS or the spectrof luorometric method in a collaborative study on high selenium wheat, flour, and toast samples. For samples with concentrations <1 μg Se/g dry wt, separation of selenium from interfering Fe and P ions by organic extraction was necessary. Using inorganic ,5 Se in meat and human milk matrixes, an ammonium pyrrolidine dithiocarbamate-methyl isobutyl ketone- extraction system with added Cu(II) as a matrix modifier yielded the best extraction recoveries, 97 and %%, respectively. Accuracy and precision of the method were tested using several official and unofficial biological standard materials. The mean accuracy was within 4% of the certified or best values of the standard materials and the day-to-day variation was 9%. The Se/Fe or Se/P interference limits proved to be low enough not to affect selenium determinations in practically all foods or diets. The practical detection limit of the method was 3 ng Se/g dry wt for 1.0 g dry wt samples. Approximately 20 duplicate determinations can be performed per day. In terms of sensitivity, accuracy, precision, and sample throughput, the tested method compares favorably with the best methods available.

scholarly journals Preconcentration and Determination of Tellurium in Garlic Samples by Hydride Generation Atomic Absorption Spectrometry

2005 ◽  
Vol 88 (4) ◽  
pp. 1242-1246 ◽  
Author(s):  
Marcos M Kaplan ◽  
Soledad Cerutti ◽  
José A Salonia ◽  
José A Gásquez ◽  
Luis D Martinez
Keyword(s):  
Standard Deviation ◽  
Atomic Absorption Spectrometry ◽  
Atomic Absorption ◽  
Hydride Generation ◽  
Absorption Spectrometry ◽  
Calibration Graph ◽  
Lanthanum Hydroxide ◽  
Relative Standard ◽  
Hydroxide Precipitate

Abstract A procedure for the determination of traces of total tellurium (Te) in garlic (Allium sativa) is described that combines hydride generation atomic absorption spectrometry with preconcentration of the analyte by coprecipitation. The samples, each spiked with lanthanum nitrate (20 mg/L), are introduced into an Amberlite XAD-4 resin and mixed with ammonium buffer (pH 9.1). Te is preconcentrated by coprecipitation with the generated lanthanum hydroxide precipitate. The precipitate is quantitatively collected in the resin, eluted with hydrochloric acid, and then transferred into the atomizer device. Considering a sample consumption of 25 mL, an enrichment factor of 10 was obtained. The detection limit (3σ) was 0.03 μg/L, and the precision (relative standard deviation) was 3.5% (n = 10) at the 10 μg/L level. The calibration graph using the preconcentration system for Te was linear with a correlation coefficient of 0.9993. Satisfactory results were obtained for the analysis of Te in garlic samples.

scholarly journals Determination of Metals in Foods by Atomic Absorption Spectrometry after Dry Ashing: NMKL1 Collaborative Study

2000 ◽  
Vol 83 (5) ◽  
pp. 1204-1211 ◽  
Author(s):  
Lars Jorhem ◽  
G Afthan ◽  
G Cumont ◽  
H P Dypdahl ◽  
K Gadd ◽  
...  
Keyword(s):  
Standard Deviation ◽  
Atomic Absorption Spectrometry ◽  
Atomic Absorption ◽  
Collaborative Study ◽  
Milk Powder ◽  
Absorption Spectrometry ◽  
Relative Standard ◽  
Dry Ashing ◽  
Zinc Concentrations

Abstract A method for determination of lead, cadmium, zinc, copper, and iron in foods by atomic absorption spectrometry (AAS) after dry ashing at 450°C was collaboratively studied in 16 laboratories. The study was preceded by a practice round of familiarization samples and another round in which solutions were distributed and the metals were determined directly by AAS. The study included 5 different foods (liver paste, apple sauce, minced fish, wheat bran, and milk powder) and 2 simulated diets. A single analysis was carried out with each sample. Suitable sample combinations were used as split-level combinations for determination of the repeatability standard deviation. The reproducibility relative standard deviation for each of the elements ranged from 20 to 50% for lead concentrations of 0.040–0.25 mg/kg, from 12 to 352% for cadmium concentrations of 0.001–0.51 mg/kg, from 4 to 8% for zinc concentrations of 0.7–38 mg/kg, from 7 to 45% for copper concentrations of 0.51–45 mg /kg, and from 11 to 14% for iron concentrations of 4–216 mg/kg.

Determination of Inorganic Tin in Biological Samples by Hydride Generation-Atomic Absorption Spectrometry after Silica Gel Cleanup

1988 ◽  
Vol 71 (2) ◽  
pp. 373-374
Author(s):  
Taizo Tsuda ◽  
Minoru Wada ◽  
Shigeru Aoki ◽  
Yoshihiro Matsui
Keyword(s):  
Standard Deviation ◽  
Atomic Absorption Spectrometry ◽  
Atomic Absorption ◽  
Silica Gel ◽  
Biological Samples ◽  
Hydride Generation ◽  
Absorption Spectrometry ◽  
Fish Muscle ◽  
Average Standard Deviation

Abstract A method is described for the determination of inorganic tin in biological samples by hydride generation-atomic absorption spectrometry (HG-AAS). A sample is extracted with ethyl acetate after addition of HC1 and NaCl. The concentrated extract is passed through a silica gel column. The column is washed with ethanol, water, and 0.2N HC1 successively, and then inorganic tin is eluted with 2N HC1 and measured by HG-AAS. Recoveries from fish muscle spiked with 0.1 ng/g Sn4+ are 78.9 ± 4.2% (average ± standard deviation, n = 5). The detection limit is 0.01 jug/g as Sn.

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.

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 Liquid Chromatographic Determination of Maleic Hydrazide in Technical and Formulated Products: Collaborative Study

2006 ◽  
Vol 89 (4) ◽  
pp. 929-936 ◽  
Author(s):  
James L Mertz ◽  
Dora Y Lau ◽  
David M Borth ◽  
E D Ausan ◽  
O Bennett ◽  
...  
Keyword(s):  
Data Analysis ◽  
Standard Deviation ◽  
Potassium Salt ◽  
Maleic Hydrazide ◽  
Collaborative Study ◽  
Laboratory Data ◽  
Internal Standard ◽  
Reversed Phase ◽  
Reproducibility Standard Deviation ◽  
Repeatability Standard Deviation

Abstract Fourteen collaborating laboratories assayed maleic hydrazide (MH), 6-hydroxypyridazin-3(2H)-one, in technical and formulated products by reversed-phase liquid chromatography (LC) with sulfanilic acid as an internal standard. The active MH in the samples (6 lots) ranged from 16% (expressed as the potassium salt) to 98% (MH in the technical). A small amount of 1 M KOH was added to the technical MH and analytical standards to create the potassium salt of the analyte which is soluble in water. Test samples and standards were extracted with water containing the internal standard before analysis by LC on a C8 column with an ion-pairing eluting solution and UV detection at 254 nm. The concentration of MH was calculated by comparing the peak area response ratios of the analyte and the internal standard with those in the analytical standard solution. Eleven laboratories weighed each test sample twice with single analysis. Three laboratories weighed each sample once and made duplicate injections on the LC system. The data were analyzed using the 11 laboratories' results. A second data analysis was done including all laboratory results using a Youden pair approach, selecting one of 2 duplicate assay values randomly for each laboratory and sample. In the first data analysis, the repeatability standard deviation ranged from 0.07 to 1.39%; reproducibility standard deviation ranged from 0.22 to 1.39%. In the second data analysis (using all laboratory data), repeatability standard deviation ranged from 0.09 to 0.86%; reproducibility standard deviation ranged from 0.22 to 1.31%.

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