Collaborative Study of a Potentiometric Method for the Determination of Fluoride in Vegetation

1975 ◽  
Vol 58 (6) ◽  
pp. 1129-1134 ◽  
Author(s):  
Jay S Jacobson ◽  
Laurence I Heller
Keyword(s):  
Reference Values ◽  
Collaborative Study ◽  
Fluoride Concentration ◽  
Practical Method ◽  
Potentiometric Method ◽  
Selective Electrode ◽  
Collaborative Test ◽  
Relative Standard ◽  
Vegetation Samples

Abstract A collaborative test was performed to evaluate a new potentiometric method for the analysis of fluoride in vegetation. The study was designed to provide estimates of accuracy and within- and between-laboratory precision of a method that employs extraction of fluoride, followed by analysis with an ion selective electrode. A group of laboratories experienced in fluoride analysis was provided with representative aliquots of specially prepared samples of vegetation and a detailed set of instructions. Reference values were established for the fluoride concentrations of vegetation samples prior to their distribution. Nine of the 23 laboratories participating in the study adhered strictly to instructions so the results from these 9 participants were used to evaluate the method. The coefficient of correlation between results from selected laboratories and reference values was 0.999. Deviations from reference values averaged 5.4% and relative standard deviations ranged from about 20% at 24 ppm to about 10% for concentrations >100 ppm fluoride. On the basis of these results, the new method has been adopted as official first action. The method is simpler and faster; it requires less equipment than the current official final action method (25.029–29.035) and can be used to estimate fluoride concentration in the foliage of plants exposed to fluorides in the atmosphere or in soils provided samples contain >10 ppm fluoride. Separate studies indicate, however, that certain samples of vegetation may be refractory to analysis by this potentiometric method. The final action method should be retained until a practical method is developed that is satisfactory for all types of vegetation.

Determination of Nitrate in Forages by Using Selective Ion Electrode: Collaborative Study

1986 ◽  
Vol 69 (2) ◽  
pp. 196-198 ◽  
Author(s):  
Michael P Carlson ◽  
Norman R Schneider ◽  
◽  
R Everson ◽  
J Johnson ◽  
...  
Keyword(s):  
Collaborative Study ◽  
Potentiometric Method ◽  
Selective Electrode ◽  
Coefficients Of Variation ◽  
Nitrate Concentrations

Abstract Each of 10 collaborating laboratories analyzed 4 blind duplicate pairs of forage samples for nitrate, by using a potentiometric method. Two forage controls and a 100 000 mg KNO3/L standard were also provided. Nitrate was extracted into an aqueous Al2(SO4)3 solution containing 70 mg KNO3/L and quantitated with a nitrate-selective electrode. Standards were prepared using extracting solution as diluent. Nitrate concentrations in forage samples ranged from <0.50 to 4.35% KNO3. Repeatability coefficients of variation (CV0) ranged from 1.74 to 3.61%, and reproducibility coefficients of variation (CV1) ranged from 6.92 to 7.66%. Mean recovery of a 0.55% KNO3 spike was 94.5%. The method has been adopted official first action.

Determination of Fluoride in Household Products by Ion-Selective Electrode and Gran’s Plot

1973 ◽  
Vol 56 (4) ◽  
pp. 798-802 ◽  
Author(s):  
Ann L Schick
Keyword(s):  
Standard Deviation ◽  
Fluoride Concentration ◽  
Thorium Nitrate ◽  
Selective Electrode ◽  
Mixed Electrolyte ◽  
Household Products ◽  
Relative Standard ◽  
Fluoride Salts ◽  
Inorganic Fluorides

Abstract In the method presented, variants from mixed electrolyte systems and interferences from complexing cations are avoided. Concentration rather than ionic activity is determined by the simplified combination of several techniques. Millivolt readings are taken as standard NaF is added to products diluted in a buffer background ; the initial fluoride concentration is then extrapolated according to Gran’s theory from a volume-corrected, semi-antilogarithmic plot. The method was applied to 12 reagents of various fluoride salts and to 10 products, including concrete etchers, stain removers, metal fluxes, metal cleaners, and oven cleaners. It could also be applied to wood preservatives and insecticides which contain fluorides. Product concentrations of fluoride ranged from 0 to 30%. Results agreed favorably with those from distillation and thorium nitrate titration methods. The standard deviation was 0.52, relative standard deviation, 2%, and standard recoveries, 98–104%. Sample preparation is adequate only for products containing inorganic fluorides. Products containing organically bound fluoride must be ashed. Eight laboratories analyzed 3 reagents and 5 products by the proposed method with excellent results. The amount of fluoride present ranged from 0 to 30%, w/v. The standard error from collaborative results ranged from 0.046 to 0.930. The method has been adopted as official first action.

Collaborative Study of Analytical Methods for Fluoride in Vegetation: Effects of Individual Techniques on Results

1972 ◽  
Vol 55 (5) ◽  
pp. 991-1003 ◽  
Author(s):  
Jay S Jacobson ◽  
D C Mccune
Keyword(s):  
Analytical Methods ◽  
Potassium Hydroxide ◽  
Collaborative Study ◽  
Dry Weight ◽  
Analytical Results ◽  
Collaborative Test ◽  
Relative Standard ◽  
Aoac Official ◽  
Vegetation Samples ◽  
Semiautomated Method

Abstract A collaborative test of analytical methods and techniques for fluoride in samples of vegetation was carried out by 64 participants and effects on the magnitude and variability of analytical results were assessed. Betweenlaboratory precision (standard deviation) for all data ranged from 2.7 ppm F for the 4 ppm sample to 53 ppm for the 365 ppm sample. Relative standard deviations ranged from 14 to 23% for the samples containing more than 27 ppm F. When data were grouped according to the techniques employed by the collaborators, statistical analyses indicated that many variations in techniques were affecting the analytical results. Both the data and the information supplied by participants support the following conclusions: (1) An explicit set of instructions, specifically designed for samples of vegetation, should be published to reduce the number of variations in analytical procedures used by different laboratories. (2) The semiautomated method, specifically developed for vegetation samples, is a preferred technique because it is simpler and faster than older methods and gives results comparable to those obtained by the Willard-Winter method. (3) The AOAC official final action method for fluoride may be used for the analysis of vegetation if the following modifications are made: Sample size should be 2–10 g dry weight; nickel, Inconel, or platinum crucibles should be used for ashing; 5 g sodium or potassium hydroxide should be used for fusion of ash at 600 °C; and 500 ml distillate should be collected. Results of this collaborative study also suggest that additional studies should be performed to discover why alkaline fixative agents used for ashing affect analytical results and whether simpler and more precise analyses will be obtained by replacing titrimetric or spectrophotometric techniques with the use of the selective ion electrode.

Comparison of the Volhard and Potentiometric Methods for the Determination of Chloride in Meat Products: Collaborative Study

1985 ◽  
Vol 68 (3) ◽  
pp. 480-484
Author(s):  
Paul R Beljaars ◽  
William Horwitz
Keyword(s):  
Sodium Chloride ◽  
Collaborative Study ◽  
Meat Products ◽  
Potentiometric Method ◽  
Collaborative Studies ◽  
Relative Standard ◽  
Luncheon Meat ◽  
Iso 5725 ◽  
Good Agreement

Abstract A collaborative study of the determination of chloride in meat products was conducted by the International Organization for Standardization (ISO) to compare the ISO 1841 method (Volhard titration) with the FAO/WHO Codex Alimentarius Committee method (potentiometric titration). Five canned luncheon meat products containing 0.25-2.0% sodium chloride at 4 different spiking levels were analyzed by 11 laboratories. The data were analyzed by ISO statistics (ISO 5725) and by AOAC statistics (Youden-Steiner), the major differences being in the rejection of outliers and in the statement of precision parameters. Good agreement was found between the mean chloride contents of the products as determined by both methods and with the added amounts, although statistically significantly higher sodium chloride recoveries were obtained with the potentiometric method. The within-laboratory variability (repeatability) is greater for the Volhard method, especially for chloride levels below 1.0%. Therefore it is proposed to set the lowest level of determination for the Volhard method at about 1.0% sodium chloride. The among-laboratories variability (reproducibility) of the potentiometric method was comparable with the results from the collaborative studies for chloride in cheese, giving acceptable values for relative standard deviations of 1.5-3.0% for meat products with 0.3-2.0% added sodium chloride. It is recommended that further work be conducted to reduce or eliminate the systematic error present with the potentiometric method as applied to meat and meat

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.

Liquid Chromatographic Determination of Glyphosate and Aminomethylphosphonic Acid (AMPA) in Environmental Water: Collaborative Study

1991 ◽  
Vol 74 (2) ◽  
pp. 317-323 ◽  
Author(s):  
Mark E Oppenhuizen ◽  
John E Cowell
Keyword(s):  
Collaborative Study ◽  
Chromatographic Determination ◽  
Environmental Water ◽  
Aminomethylphosphonic Acid ◽  
Relative Standard ◽  
Total Variability ◽  
Liquid Chromatographic Determination ◽  
Predicted Values ◽  
Liquid Chromatographic

Abstract A new method for determination of glyphosate and amlnomethylphosphonlc acid (AMPA) residues In environmental water was collaboratively studied by 6 laboratories. The method Is simpler and shorter than previous methods. A filtered volume of water is evaporated to dryness and the residue Is dissolved In a buffered EDTA solution. Glyphosate and AMPA are determined by liquid chromatography with postcolumn reaction detection. The method was validated over the range 0.50-5000 ppb, although one of the collaborating laboratories could not reliably quantltate below 1.0 ppb. Statistical analysis of the results showed that typical reproducibility relative standard deviations (RSDR) ranged from 11 to 20% for both glyphosate and AMPA, which compares very well with predicted values for this concentration range. Total variability (as measured by sR) Increased with increasing fortification level. The method has been adopted official first action by AOAC.

Determination of inorganic fluoride in blood with a fluoride ion-selective electrode.

1987 ◽  
Vol 33 (2) ◽  
pp. 253-255 ◽  
Author(s):  
E Kissa
Keyword(s):  
Whole Blood ◽  
Fluoride Concentration ◽  
Ion Selective Electrode ◽  
Fluoride Ion ◽  
Inorganic Fluoride ◽  
Selective Electrode ◽  
Cell Potential ◽  
Novel Method ◽  
Fluoride Ion Selective Electrode

Abstract Inorganic fluoride in whole blood, serum, or plasma has been determined with a fluoride ion-selective electrode by adding the 0.5- to 2.0-mL sample to 20 mL of water containing a buffer and fluoride, 25 micrograms/L. The fluoride concentration in the sample is calculated from the resulting cell potential difference recorded after equilibrating for 10 min. This novel method has the advantages of simplicity, accuracy, and high precision, standard deviations for 5 to 7 replicate determinations of fluoride ranging from +/- 1.7 to +/- 2.4 micrograms/L. For whole blood from donors living in an area with fluorinated drinking water, the F- concentration was 20 to 60 micrograms/L.

Determination of Maleic Hydrazide Residues in Tobacco and Vegetables

1973 ◽  
Vol 56 (5) ◽  
pp. 1164-1172
Author(s):  
Milan Ihnat ◽  
Robert J Westerby ◽  
Israel Hoffman
Keyword(s):  
Standard Deviation ◽  
Present Method ◽  
Maleic Hydrazide ◽  
Collaborative Study ◽  
Official Method ◽  
Sample Weight ◽  
Relative Standard ◽  
The Mean ◽  
Pipe Tobacco

Abstract The distillation-spectrophotometric method of Hoffman for determining maleic hydrazide has been modified to include a double distillation and was applied to the determination of 1–30 ppm maleic hydrazide residues in tobacco and vegetables. Recoveries of 1–23 μg added maleic hydrazide were independent of weight of maleic hydrazide, but did depend on sample and sample weight. The following recoveries were obtained from 0.5 g sample: pipe tobacco, 84%; commercially dehydrated potato, 83%; cigar tobacco, 81%; dried potato, 76%; fluecured tobacco, 73%; dried carrot, 71%. In the absence of sample, the recovery was 82%. When appropriate standard curves were used, maleic hydrazide levels determined in tobacco samples were essentially independent of sample weight in the range 0.1–3 g. The mean relative standard deviation for a variety of field-treated and fortified tobacco samples containing 1–28 ppm maleic hydrazide was 3%. The precision and sensitivity of this procedure seem to be substantial improvements over official method 29.111–29.117. It is recommended that the present method be subjected to a collaborative study.

scholarly journals Liquid Chromatographic Determination of Ampicillin Residues in Porcine Muscle Tissue by a Multipenicillin Analytical Method: European Collaborative Study

2002 ◽  
Vol 85 (4) ◽  
pp. 889-900 ◽  
Author(s):  
Eric Verdon ◽  
Pierric Couëdor ◽  
Pierre Maris ◽  
Michel Laurentie ◽  
P Batjoens ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Standard Deviation ◽  
Relative Standard Deviation ◽  
Muscle Tissue ◽  
Phosphate Buffer ◽  
Collaborative Study ◽  
Porcine Muscle ◽  
Relative Standard ◽  
Liquid Chromatographic

Abstract A collaborative study involving 14 laboratories was conducted to determine residues of ampicillin in porcine muscle tissue by using a liquid chromatographic method developed for multipenicillin analysis that can quantitate 8 penicillin compounds (benzylpenicillin, phenoxymethylpenicillin, ampicillin, amoxicillin, nafcillin, oxacillin, cloxacillin, and dicloxacillin) at trace levels in muscle tissue. This method involves extraction of the penicillins with phosphate buffer, pH 9, followed cleanup and concentration on a C18 solid-phase extraction column and reaction with benzoic anhydride at 50°C and with 1,2,4-triazole and mercury(II) chloride solution, pH 9.0, at 65°C. The derivatized compounds are eluted isocratically on a C8 column with a mobile phase of acetonitrile and phosphate buffer (pH 6; 0.1M) containing sodium thiosulfate and the ion-pair reagent tetrabutylammonium hydrogen sulfate. The penicillins are detected by UV absorption at 325 nm. The limit of detection and the limit of determination (quantitation) of the method were calculated to be approximately 3–5 and 25 μg/kg, respectively, in accordance with the criteria of European Union (EU) Decision No. 93/256/EEC. In this first interlaboratory study, collaborators were instructed to monitor 4 different penicillin compounds (benzylpenicillin, phenoxymethylpenicillin, ampicillin, and amoxicillin) by analyzing 8 blind samples of muscle tissue in triplicate. These samples were prepared from 2 materials containing different concentrations of incurred ampicillin (63.5 μg/kg for material No. 1 and 358.1 μg/kg for material No. 2) and 1 blank material. The repeatability relative standard deviation and the reproducibility relative standard deviation were 10.2 and 17.4%, respectively, for material No. 1 and 7.0 and 16.0%, respectively, for material No. 2. These results demonstrate that the method is suitable for the determination of ampicillin residues in muscle tissue at the EU maximum residue limit (50 μg/kg) and above. However, the identification of positives by this procedure may need additional confirmation by techniques with greater specificity, such as liquid chromatography combined with mass spectrometry, or tandem mass spectrometry. Investigations regarding the basis of interlaboratory testing studies will further demonstrate the suitability of multiresidue methodology for detecting and quantitating other compounds in the family of penicillin antibiotics.

Gas Chromatographic-Thermal Energy Analysis Method for Determination of Volatile N-Nitrosamines in Baby Bottle Rubber Nipples: Collaborative Study

1987 ◽  
Vol 70 (1) ◽  
pp. 64-68 ◽  
Author(s):  
J Ian Gray ◽  
Michael A Stachiw
Keyword(s):  
Thermal Energy ◽  
Energy Analysis ◽  
Collaborative Study ◽  
Internal Standard ◽  
Analytical Techniques ◽  
The United States ◽  
Baby Bottle ◽  
Relative Standard ◽  
Better Than

Abstract A collaborative study was conducted on the U.S. Food and Drug Administration (FDA) dichloromethane extraction method for determining volatile N-nitrosamines in baby bottle rubber nipples. Following dichloromethane extraction, A'-nitrosamines were determined by gas chromatography-thermal energy analysis. Six pairs of blind duplicate rubber nipple samples representing 6 lots were analyzed by 11 collaborating laboratories. All samples were portions taken from equilibrated composites of cut-up rubber nipples obtained from manufacturers in the United States. Recoveries of the internal standard (N-nitrosodipropylamine) at approximately 20 ppb ranged from 10 to 120%. Reproducibility relative standard deviations (RSDJ were between 35 and 45% for N-nitrosamine levels from 10 to 20 ppb. However, when data from laboratories with recoveries less than 75% were excluded (this is now specified in the method), RSD„ values were between 11 and 32% for N-nitrosamine levels from 6 to 26 ppb. Values were consistent with or better than those reported for other analytical techniques designed to quantitate trace contaminants at the low ppb level, e.g., afiatoxin in foods. The method has been adopted official first action for the quantitation of volatile N-nitrosamines in baby bottle rubber nipples.

Sign in / Sign up

Export Citation Format

Share Document