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 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.

Enzymatic hydrolysis of chitosan in acetate buffer solution

2015 ◽  
Vol 88 (4) ◽  
pp. 647-651 ◽  
Author(s):  
V. V. Chernova ◽  
A. S. Shurshina ◽  
M. V. Bazunova ◽  
E. I. Kulish
Keyword(s):  
Enzymatic Hydrolysis ◽  
Acetate Buffer ◽  
Acetate Buffer Solution ◽  
Buffer Solution ◽  
Hydrolysis Of

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.

Analysis of Ochratoxins A and B and Their Esters in Barley, Using Partition and Thin Layer Chromatography. II. Collaborative Study

1973 ◽  
Vol 56 (4) ◽  
pp. 822-826
Author(s):  
Stanley Nesheim
Keyword(s):  
Thin Layer ◽  
Ochratoxin A ◽  
Coefficient Of Variation ◽  
Collaborative Study ◽  
Ethyl Esters ◽  
The Other ◽  
Average Recovery ◽  
Confirmation Test ◽  
Two Samples ◽  
Layer Chromatography

Abstract To test the method of Nesheim et al., 6 samples wert; analyzed in 13 laboratories. The samples encompassed a blank and 5 samples containing one or more ochratoxins in the range 50–200 μg/kg. Two samples were spiked with the 4 ochratoxin standards and 3 were spiked with barley naturally contaminated with ochratoxin A. The confirmation of identity of ochratoxins A and B by preparation of their ethyl ester derivatives was also tested. The average recovery of standard ochratoxin A was 112% at levels of 45 and 90 μg/kg, with a 27.1% coefficient of variation calculated from analysis of variance, one analyst, one replicate. Similar satisfactory results were obtained for the ethyl esters of A and B at a level of 120 μg/kg. The results were unsatisfactory for ochratoxin B and for the esters of A and B at the 60 μg/kg level. The chemical confirmation test was satisfactory for both ochratoxins A and B. The method, including chemical confirmation, has been adopted as official first action as quantitative for ochratoxin A and qualitative for the other toxins.

Preparation and characterization of a poly-o-phenylenediamine film modified glassy carbon electrode as a H2O2 sensor

2013 ◽  
Vol 91 (11) ◽  
pp. 1077-1084 ◽  
Author(s):  
Wenying Zhai ◽  
Xiuying Tian ◽  
Yun Yan ◽  
Yuehua Xu ◽  
Yuechun Zhao ◽  
...  
Keyword(s):  
Cyclic Voltammetry ◽  
Glassy Carbon Electrode ◽  
Glassy Carbon ◽  
Electrochemical Impedance ◽  
Monomer Concentration ◽  
Acetate Buffer ◽  
Acetate Buffer Solution ◽  
Carbon Electrode ◽  
Modified Glassy Carbon Electrode ◽  
Buffer Solution

A poly-o-phenylenediamine film modified glassy carbon electrode (PoPD/GC) was successfully prepared by cyclic voltammetry in acetate buffer solution. The polymerization mechanism of oPD is discussed. The impedance behavior and morphology of the PoPD membrane were characterized using cyclic voltammetry, electrochemical impedance spectroscopy, and scanning electron microscopy, respectively. It is discovered that the PoPD/GC prepared only in acetate buffer solution had dual electrocatalytic activity toward the oxidation and reduction of H2O2. The optimal buffer solution pH, scanning rate, monomer concentration, and number of scannings for film forming were 4.2, 0.05 V s−1, 6.0 mmol L−1, and 30, respectively. The linear ranges between the anodic (Δia) or cathodic (Δic) current and H2O2 concentration were 0.07−1.0 × 104 and 0.04−4.5 × 104 μmol L−1, respectively. The corresponding calibration curves were Δia (μA) = 8.03c (mmol L−1) + 6.36 (n = 18, R2 = 0.9989) and Δic (μA) = −5.52c (mmol L−1) − 0.77 (n = 18, R2 = 0.9990) with a detection limit of 0.03 and 0.02 μmol L−1 (S/N = 3), respectively. The PoPD/GC prepared in the optimal conditions showed good stability and quick response (<0.2 s) to H2O2, which was successfully applied to the determination of H2O2 in real water samples with satisfactory results.

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