Collaborative Study of Modified Elmore Method for Mercury in Formulations

1971 ◽  
Vol 54 (3) ◽  
pp. 685-687
Author(s):  
James E Launer
Keyword(s):  
Standard Deviation ◽  
Systematic Error ◽  
Random Error ◽  
Collaborative Study ◽  
Test Pair ◽  
Titrimetric Method ◽  
Mercuric Nitrate ◽  
Thiocyanate Solution ◽  
Diluted Solution ◽  
Bearing Materials

Abstract The titrimetric method for mercury described by Elmore in 1946 was modified and collaboratively studied with formulations containing 6.7% phenylmercury urea in one test pair and 1% mercuric nitrate in another test pair. Mercury is determined in diluted solution, following reflux at 30 drops/min with fuming H2SO4-red fuming HNO3, by titration with standard thiocyanate solution, using ferric alum as indicator. The method is not applicable in presence of large quantities of chlorine-bearing materials. Single determinations on 4 samples by 14 collaborators showed that the standard deviation estimation of random error was 0.058 for phenylmercury urea and 0.004 for mercuric nitrate. Standard deviation estimates of systematic error were 0.048 and 0.009, respectively. The method has been adopted as official first action.

Collaborative Study of a Colorimetric Method for Paraquat in Formulations

1968 ◽  
Vol 51 (6) ◽  
pp. 1306-1309
Author(s):  
A A Carlstrom
Keyword(s):  
Free Radical ◽  
Standard Deviation ◽  
Systematic Error ◽  
Random Error ◽  
Collaborative Study ◽  
Colorimetric Method ◽  
Sodium Dithionite ◽  
Reference Standard ◽  
Standard Curve ◽  
Diluted Solution

Abstract A colorimetric method described by Yuen, Bagness, and Myles in 1967 was collaboratively studied with paraquat formulations containing 2 lb/gal. (about 20% cation). Paraquat is determined in a diluted solution by measuring the absorbance, at 600 mμ, of the blue free radical produced by reduction with alkaline sodium dithionite, and its absorbance is compared to a reference standard curve. Standard deviation estimation of random error was 0.22 for paraquat dimethylsulfate formulations and 0.26 for paraquat dichloride. Standard deviation estimates of systematic error were 0.20 and 0.62, respectively. The method is recommended for adoption as official, first action.

Collaborative Study of Betaine in Orange Juice

1970 ◽  
Vol 53 (3) ◽  
pp. 568-571
Author(s):  
Grayson R Rogers
Keyword(s):  
Amino Acids ◽  
Standard Deviation ◽  
Ion Exchange ◽  
Systematic Error ◽  
Orange Juice ◽  
Collaborative Study ◽  
Colorimetric Method ◽  
Actual Data ◽  
Random Errors ◽  
Water Solutions

Abstract An ion exchange-colorimetric method for determining betaine in orange juice was studied by 11 collaborators on 4 orange juice samples and 2 synthetic water solutions consisting of sucrose, dextrose, and various amino acids found in orange juice. Average recoveries in the collaborative study were 96.7 and 95.9%. Results show that the precision standard deviation among laboratories is generally acceptable. The distribution of the actual data is greater than normally expected, but random errors appear to be responsible since no significant systematic error can be detected in the data. The method is recommended for adoption as official first action.

Collaborative Study of an Ultraviolet Method for Measuring Diquat Content in Formulations

1968 ◽  
Vol 51 (6) ◽  
pp. 1304-1305
Author(s):  
A A Carlstrom
Keyword(s):  
Systematic Error ◽  
Random Error ◽  
Coefficient Of Variation ◽  
Collaborative Study ◽  
Acetate Buffer ◽  
Acetate Buffer Solution ◽  
Buffer Solution ◽  
Standard Curve ◽  
Two Samples

Abstract The ultraviolet method for diquat described by Yuen, Bagness, and Myles in 1967 was collaboratively studied with formulations containing 2 lb diquat/gal. A portion of the sample is diluted with an acetate buffer solution and the absorbance is measured at 310 mμ the diquat content is obtained by reference to a standard curve prepared from known diquat concentrations. Single determinations on two samples by thirteen collaborators show an overall coefficient of variation of 2.4%. The coefficient of variation for random error is 1.0%, and for systematic error 1.6%. The method is recommended for adoption 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°.

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 Gravimetric Method for Mercury in Formulations Containing Chlorinated Pesticides

1973 ◽  
Vol 56 (3) ◽  
pp. 572-575
Author(s):  
James E Launer
Keyword(s):  
Standard Deviation ◽  
Close Agreement ◽  
Collaborative Study ◽  
Gravimetric Method ◽  
Test Pair ◽  
H2so4 Solution ◽  
Chlorinated Pesticides ◽  
Mercury Iodide ◽  
Digestion Mixture ◽  
Preliminary Study

Abstract A gravimetric method for mercury was modified and collaboratively studied with formulations containing ~6% phenylmercuric urea and ~7% captan in one test pair and ~2% phenylmercuric urea and 30% lindane in another test pair. Mercury is determined by precipitation and weighing cupric propylene mercury iodide (Cu pn2HgI4), following refluxing with dilute HI-H2SO4 solution containing I2. Single determinations on 4 samples by 11 collaborators showed that the standard deviation estimation of random error was 0.063 for the captan pair and 0.034 for the lindane pair. Standard deviation estimates of systematic error were 0.061 and 0.013, respectively. In the preliminary study, the method showed close agreement with other accepted methods for 15 formulations. Lindane, captan, dieldrin, heptachlor, and zineb do not interfere; however, the method is not applicable to chloro- or nitrophenolic compounds nor to materials not decomposed by the digestion mixture. The method has been adopted as official first action.

Error Analysis and Modeling of GPM Dual-Frequency Precipitation Radar Near-surface Rainfall Product

2021 ◽  
Keyword(s):  
Standard Deviation ◽  
Systematic Error ◽  
Random Error ◽  
Convective Precipitation ◽  
Dual Frequency ◽  
Precipitation Radar ◽  
Near Surface ◽  
Surface Rainfall ◽  
Comparison Results ◽  
Stratiform Precipitation

Abstract The error characterization of rainfall products of spaceborne radar is essential for better applications of radar data, such as multi-source precipitation data fusion and hydrological modeling. In this study, we analyzed the error of the near-surface rainfall product of the dual-frequency precipitation radar (DPR) on the Global Precipitation Measurement Mission (GPM) and modeled it based on ground C-band dual-polarization radar (CDP) data with optimization rainfall retrieval. The comparison results show that the near-surface rainfall data were overestimated by light rain and slightly underestimated by heavy rain. The error of near-surface rainfall of the DPR was modeled as an additive model according to the comparison results. The systematic error of near-surface rainfall was in the form of a quadratic polynomial, while the systematic error of stratiform precipitation was smaller than that of convective precipitation. The random error was modeled as a Gaussian distribution centered at −1−0 mm h−1. The standard deviation of the Gaussian distribution of convective precipitation was 1.71 mm h−1 and the standard deviation of stratiform precipitation was 1.18 mm h−1, which is smaller than that of convective precipitation. In view of the precipitation retrieval algorithm of DPR, the error causes were analyzed from the reflectivity factor (Z) and the drop size distribution (DSD) parameters (Dm, Nw). The high accuracy of the reflectivity factor measurement results in a small systematic error. Importantly, the negative bias of Nw was very obvious when the rain type was convective precipitation, resulting in a large random error.

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 Titrimetric Method for the Assay of Amitrole Formulations

1967 ◽  
Vol 50 (3) ◽  
pp. 568-572
Author(s):  
J Russell Bishop
Keyword(s):  
Collaborative Study ◽  
Statistical Analyses ◽  
Standard Samples ◽  
Titrimetric Method ◽  
Inflection Points ◽  
Good Agreement

Abstract titrimetric method for the assay of dry and liquid amitrole formulations was studied by 10 collaborators. In the method, acid is added to the prepared amitrole sample, the solution is titrated potentiometrically with standard alkali, and the amitrole content is measured as the amount of alkali consumed between the first and second inflection points. Collaborative results on standard samples of a dry 90% formulation, a dry 50% formulation, and a liquid 2 lb/gallon formulation showed good agreement between samples and laboratories. Statistical analyses of the results were satisfactory, and the method for the assay of amitrole formulations is recommended for adoption as official, first action

scholarly journals Indirect and Direct Determination of the Casein Content of Milk by Kjeldahl Nitrogen Analysis: Collaborative Study

1998 ◽  
Vol 81 (4) ◽  
pp. 763-774 ◽  
Author(s):  
Joanna M Lynch ◽  
David M Barbano ◽  
J Richard Fleming
Keyword(s):  
Standard Deviation ◽  
Nitrogen Content ◽  
Relative Standard Deviation ◽  
Collaborative Study ◽  
Direct Determination ◽  
Raw Milk ◽  
Method Performance ◽  
Relative Standard ◽  
Milk Casein

Abstract The classic method for determination of milk casein is based on precipitation of casein at pH 4.6. Precipitated milk casein is removed by filtration and the nitrogen content of either the precipitate (direct casein method) or filtrate (noncasein nitrogen; NCN) is determined by Kjeldahl analysis. For the indirect casein method, milk total nitrogen (TN; Method 991.20) is also determined and casein is calculated as TN minus NCN. Ten laboratories tested 9 pairs of blind duplicate raw milk materials with a casein range of 2.42- 3.05℅ by both the direct and indirect casein methods. Statistical performance expressed in protein equivalents (nitrogen ⨯ 6.38) with invalid and outlier data removed was as follows: NCN method (wt%), mean = 0.762, sr = 0.010, SR = 0.016, repeatability relative standard deviation (RSDr) = 1.287℅, reproducibility relative standard deviation (RSDR) = 2.146%; indirect casein method (wt℅), mean = 2.585, repeatability = 0.015, reproducibility = 0.022, RSDr = 0.560℅, RSDR = 0.841; direct casein method (wt℅), mean = 2.575, sr = 0.015, sR = 0.025, RSDr = 0.597℅, RSDR = 0.988℅. Method performance was acceptable and comparable to similar Kjeldahl methods for determining nitrogen content of milk (Methods 991.20, 991.21,991.22, 991.23). The direct casein, indirect casein, and noncasein nitrogen methods have been adopted by AOAC INTERNATIONAL.

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