Collaborative Study of a Fluorometric Method for Determining Selenium in Foods

1974 ◽  
Vol 57 (2) ◽  
pp. 373-378 ◽  
Author(s):  
Milan Ihnat
Keyword(s):  
Standard Deviation ◽  
Systematic Error ◽  
Collaborative Study ◽  
Bovine Liver ◽  
Standard Reference Materials ◽  
Fluorometric Method ◽  
Naturally Occurring ◽  
Coefficients Of Variation ◽  
Error Standard Deviation

Abstract A fluorometric method for the determination of selenium in foods reported previously was studied collaboratively. Nineteen laboratories reported analytical results on 10 samples representative of vegetables, cereal, dairy products, meat, and fish, and containing naturally occurring selenium. For the 5 pairs of samples, the coefficients of variation based on precision standard deviation were 2 5 . 9% at 16 ng selenium, 15.8% at 98 ng, 8.5% at 233 ng, 6.1% at 379 ng, and 4.1 % at 427 ng. The corresponding coefficients of variation computed from overall standard deviations were 65.3, 17.5, 8.9, 8.1, and 5.6%. Systematic error was significant for 2 pairs (F-test, p = 0.01), but not for the remaining 3 (p = 0.05). The ratio of the systematic error standard deviation to the precision standard deviation varied from 0.21 to 1.64. Analyses of 2 NBS standard reference materials, orchard leaves (75 ng selenium) and bovine liver (208 ng selenium), yielded results higher by 16 and 10%, respectively. The precision and accuracy of the collaborative procedure were deemed acceptable and the method has been adopted as official first action.

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.

Collaborative Study of a Semiautomated Fluorometric Method for the Determination of Reserpine in Tablets

1976 ◽  
Vol 59 (2) ◽  
pp. 289-292
Author(s):  
Mary A Kreienbaum
Keyword(s):  
Vanadium Pentoxide ◽  
Collaborative Study ◽  
Dosage Level ◽  
Fluorometric Method ◽  
Coefficients Of Variation ◽  
Semiautomated Method

Abstract A semiautomated fluorometric method for the determination of resperpine in tablets was collaboratively studied by 7 laboratories. The method is a modification of the semiautomated method of Urbányi and Stober, which involves formation of a fluorogen with vanadium pentoxide. Collaborators were supplied with 3 composites, each from a different dosage level of commercial tablets. The results obtained agreed well with the AOAC manual fluorometric method; coefficients of variation ranged from 0.45 to 2.70%. The method has been adopted as official first action.

Collaborative Study of the Thermistor Cryoscopic Method for the Determination of the Freezing Point Value of Milk

1968 ◽  
Vol 51 (4) ◽  
pp. 816-821
Author(s):  
R W Henningson
Keyword(s):  
Standard Deviation ◽  
Systematic Error ◽  
Freezing Point ◽  
Collaborative Study

Abstract Data from 19 collaborators for two sample pairs were used to estimate the precision and systematic error of the thermistor cryoscopic method for determining the freezing point value of milk. Precision was greater for the milks (0.0015°) than for the standards (0.004°). The systematic error was estimated to be 0.0033°. The standard deviation for interlaboratory individual determinations was estimated to be 0.0049°.

Determination of Vitamin E in Foods and Feeds—A Collaborative Study

1971 ◽  
Vol 54 (1) ◽  
pp. 1-12 ◽  
Author(s):  
Stanley R Ames
Keyword(s):  
Vitamin E ◽  
Collaborative Study ◽  
Tocopheryl Acetate ◽  
Weighted Mean ◽  
Naturally Occurring ◽  
Coefficients Of Variation ◽  
Supplemental Vitamin ◽  
Reducing Substances ◽  
Official Procedure

Abstract A collaborative study was conducted to evaluate a method for the determination of vitamin E in foods and feeds. Both the naturally occurring and the supplemental vitamin E are extracted from the sample by the appropriate procedure, the lipid residue is saponified, and α-tocopherol is isolated by TLC and determined colorimetrically. To determine supplemental a-tocopheryl acetate specifically, the sample is extracted by the appropriate procedure, reducing substances including natural atocopherol are removed by oxidative chromatography, the a-tocopheryl acetate is saponified, and the resulting a-tocopherol is determined colorimetrically. These assays for vitamin E in foods and feeds are neither rapid nor easy and considerable skill is required to obtain reliable results. Data reported by 7 collaborators on 7 samples indicate that the standard deviation among laboratories is not significant for the determination of total α-tocopherol but is significant for the determination of supplemental a-tocopheryl acetate. The weighted mean coefficients of variation were 11.0% for the determination of total a-tocopherol and 7.0% for the determination of supplemental a-tocopheryl acetate. Since an official procedure for the determination of vitamin E in foods and feeds is needed and since most laboratories were successful in carrying out the procedure, the Associate Referee recommends that the method as modified be adopted as official first action.

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.

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.

Collaborative Study of a Spectrophotometric Method for Determining Maleic Hydrazide Residues in Tobacco and Vegetables

1975 ◽  
Vol 58 (6) ◽  
pp. 1235-1243
Author(s):  
Milan Ihnat ◽  
Brian Thompson
Keyword(s):  
Standard Deviation ◽  
Spectrophotometric Method ◽  
Strong Evidence ◽  
Maleic Hydrazide ◽  
Collaborative Study ◽  
Green Bean ◽  
F Test ◽  
Coefficients Of Variation ◽  
Better Than

Abstract A distillation-spectrophotometric method for the determination of maleic hydrazide residues in tobacco and vegetables reported previously was studied collaboratively. Ten laboratories submitted analytical results on 10 samples containing residues resulting either from field treatment or laboratory fortification. The samples were estimated to contain from 0.99 to 16.36 μg maleic hydrazide/0.5 g sample analyzed. The coefficients of variation based on precision standard deviation ranged from 57.7% for the lowest residue content to 32.4% for the highest. The corresponding coefficients of variation based on overall standard deviations were estimated to be at least one-fifth larger. Strong evidence of systematic laboratory differences was found (F-test, significant at 0.1%). Apparent recoveries of 10.0 fifl maleic hydrazide added to 0.5 g fluecured tobacco and potato were 97.3 and 89.7%, respectively. Apparent recoveries of 16.0 and 16.5 μg added to 0.5 g green bean were 87.4 and 85.5%, respectively. The precision of the method studied was no better than that of the current official final action method, 29.121–29.127, and its adoption is not recommended.

Determination of Diagnostic Levels of Arsenic in Animal Tissue: Collaborative Study

1986 ◽  
Vol 69 (3) ◽  
pp. 493-495
Author(s):  
R Tracy Hunter ◽  
◽  
G H D’Andrea ◽  
R J Audette ◽  
B Colvin ◽  
...  
Keyword(s):  
Collaborative Study ◽  
Bovine Liver ◽  
Animal Tissue ◽  
National Bureau ◽  
Oyster Tissue ◽  
Zinc Metal ◽  
Coefficients Of Variation ◽  
Aoac Method

Abstract The method chosen for this collaborative study is a modification of the AOAC method for As residues, 41.009-41.012. The tissue is dry-ashed overnight at 500°C, and then dissolved in dilute HCl. The solution is diluted and an aliquot is reacted with zinc metal to evolve arsine gas. The gas is trapped in AgDDC solution and As is quantitated at 540 nm. Nine collaborating laboratories performed single analyses on 4 blind duplicate pairs of bovine liver samples which were spiked at 0, 4.3, 10.8, or 21.6 mg As/kg liver. A National Bureau of Standards control (SRM 1566 Oyster Tissue, 13.4 ± 1.9 mg As/kg) and a 1000 mg As/L standard were also submitted to the collaborators. Intralaboratory coefficients of variation ranged from 7.7 to 17.8%; interlaboratory coefficients of variation ranged from 10.9 to 19.0%. The method has been adopted official first action.

Fluorometric Determination of Estradiol Valerate in Sesame Oil or Ethyl Oleate Injectables. II. Collaborative Study

1973 ◽  
Vol 56 (1) ◽  
pp. 86-87
Author(s):  
Theron James
Keyword(s):  
Collaborative Study ◽  
Ethyl Oleate ◽  
Sesame Oil ◽  
Estradiol Valerate ◽  
Fluorometric Method ◽  
Fluorometric Determination ◽  
Coefficients Of Variation

Abstract A fluorometric method for determining estradiol valerate in sesame oil or ethyl oleate was subjected to collaborative study. The method utilizes a nitromethane-Celite column to isolate and purify the steroid, which is then measured fluorometrically. Four commercial samples and 3 synthetic samples, varying in concentration from 4 to 20 mg/ml, were used in the study. The collaborative results were acceptable: Coefficients of variation ranged from 2.48 to 3.55%; average recoveries for the synthetics ranged from 98.6 to 102%. The method has been adopted as official first action.

Atomic Absorption Spectrophotometric Determination of Liver Copper: Collaborative Study

1985 ◽  
Vol 68 (1) ◽  
pp. 44-45 ◽  
Author(s):  
David L Osheim ◽  
Frank P Ross
Keyword(s):  
Atomic Absorption ◽  
Limit Of Detection ◽  
Collaborative Study ◽  
Bovine Liver ◽  
Atomic Absorption Spectrophotometry ◽  
National Bureau ◽  
Liver Sample ◽  
Liver Copper ◽  
Coefficients Of Variation

Abstract Eleven collaborating laboratories conducted replicate analyses on 4 blind duplicate pairs of bovine liver samples that either had naturally acquired copper levels or were spiked with one of 3 copper levels. A National Bureau of Standards Bovine Liver sample (SRM 1577, 193 ± 10 mg copper/kg) and a 1000 mg copper/L standard were also submitted to the collaborators. The method requires the tissue to be digested with concentrated HN03 at 60°C, diluted to volume with water, and analyzed by atomic absorption spectrophotometry. The intralaboratory coefficients of variation (CV„) ranged from 5.6 to 19%; the interlaboratory CVX values ranged from 7.1 to 21%. The lower limit of detection was estimated to be 1 mg copper/kg tissue. The method has been adopted official first action.

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