Determination of Volatile Bases in Seafood Using the Ammonia Ion Selective Electrode: Collaborative Study

Abstract Nine collaborating laboratories tested a combination of 23 seafood samples for volatile bases using an ammonia ion selective electrode. Results were reported as mg NH3/100 g fish, but the method reflected levels of both ammonia and trimethylamine, which permeated the ammonia membrane. The 23 samples were broken down into 8 blind duplicate pairs, 2 Youden matched pairs, and 3 single samples covering fresh to spoiled product ranging from 8 to 82 mg NH3/100 g. Seven species were evaluated: Atlantic cod, squid, Atlantic halibut, gray sole, monkfish, dogfish, and Atlantic mackerel. The ammonia electrode assay was performed on an aqueous homogenate consisting of 95 mL distilled water and 5.0 g sample tissue. Alkaline ion strength adjusting solution (2 mL) was added to the homogenate to liberate ammonia that was sensed by the ion specific electrode and measured on a precalibrated portable meter. Repeatability standard deviations (RSDr) ranged from 4.2 to 17%; reproducibility standard deviations (RSDR) ranged from 8.8 to 21%. A standard ammonium chloride solution was provided to all laboratories to spike 3 different samples at 10 mg NH3/100 g. Recoveries of added ammonia as ammonium chloride for fresh, borderline, and spoiled samples were 88.6, 107, and 128%, respectively.

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Collaborative Study of Ion Selective Electrode Method for the Direct Determination of Fluoride in Feeds

Journal of AOAC INTERNATIONAL ◽

10.1093/jaoac/58.3.477 ◽

1975 ◽

Vol 58 (3) ◽

pp. 477-481 ◽

Cited By ~ 1

Author(s):

Laszlo Torma

Keyword(s):

Standard Deviation ◽

Collaborative Study ◽

Direct Determination ◽

Ion Selective Electrode ◽

Official Method ◽

Selective Electrode ◽

Standard Curve ◽

Electrode Method ◽

Aoac Method

Abstract A rapid and precise method for the determination of fluoride in feeds employs HC1 extraction of the sample. Acetate buffer and sodium citrate are added to control pH and ionic strength. The amount of fluoride is calculated from a standard curve after measuring the potentials of standard and sample solutions. Eight collaborators participated in the study of the method. Statistical values on 3 pairs of samples were calculated. The standard deviation, precision, coefficient of variation, and bias, respectively, were: Pair 1, 0.005071, 0.001763, 3.09, 0.0034; Pair 2, 0.037122, 0.006475, 1.82, 0.0258; Pair 3, 0.034587, 0.013021, 2.63, 0.0227. The results from the proposed method agreed favorably with the values obtained by using the official final action AOAC method, 7.089. The average and standard deviation, respectively, for individual samples by the proposed method were: Sample 3, 0.049, 0.0029; Sample 4, 0.059, 0.0021; Sample 5, 0.334, 0.0114; Sample 6, 0.341, 0.0101; Sample 7, 0.511, 0.0219; Sample 8, 0.492, 0.0237. By the official method the values were: Sample 3, 0.049, 0.0041; Sample 4, 0.058, 0.0029; Sample 5, 0.334, 0.0055; Sample 6, 0.331, 0.0082; Sample 7, 0.517, 0.0183; Sample 8, 0.499, 0.0175. The ion selective electrode method has been adopted as official first action.

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Enzymatic-Ultraviolet Determination of Glucose and Fructose in Wine: Collaborative Study

Journal of AOAC INTERNATIONAL ◽

10.1093/jaoac/68.5.1021 ◽

1985 ◽

Vol 68 (5) ◽

pp. 1021-1024 ◽

Cited By ~ 1

Author(s):

Guenther Henniger ◽

Leonard Mascaro

Keyword(s):

Nicotinamide Adenine Dinucleotide ◽

Collaborative Study ◽

Nicotinamide Adenine Dinucleotide Phosphate ◽

Phosphoglucose Isomerase ◽

Nicotinamide Adenine ◽

Matched Pairs ◽

Repeatability And Reproducibility ◽

Standard Deviations ◽

Glucose 6 Phosphate Dehydrogenase

Abstract This collaborative study on the determination of glucose and fructose in wine was performed by 18 laboratories on 4 matched pairs of commercial wine. The method uses the enzymes hexokinase, glucose-6- phosphate dehydrogenase, and phosphoglucose isomerase and the coenzyme nicotinamide-adenine dinucleotide phosphate. Both glucose and fructose can be determined in the same sample without separation. The method is simple but care is necessary to ensure precise transfer of small volumes. Repeatability and reproducibility standard deviations for glucose ranged from 2.6 to 14.6 mg/L and 4.7 to 16.5 mg/L, respectively. Repeatability and reproducibility values for fructose ranged from 2.4 to 16.1 mg/L and 6.0 to 21.3 mg/L, respectively. The method has been adopted official first action

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Determination of Fluoride in Fluoride Tablets and Solutions by Ion-Selective Electrode: Collaborative Study

Journal of AOAC INTERNATIONAL ◽

10.1093/jaoac/67.4.682 ◽

1984 ◽

Vol 67 (4) ◽

pp. 682-684

Author(s):

John R Marzilli ◽

◽

F L Acampora ◽

L R Alexander ◽

M Y Alpert ◽

...

Keyword(s):

Sodium Fluoride ◽

Collaborative Study ◽

Ion Selective Electrode ◽

Ion Concentration ◽

Fluoride Ion ◽

Selective Electrode ◽

Mean Values ◽

Coefficients Of Variation

Abstract A proposed method using the fluoride (F) ion-selective electrode has been developed for determining the fluoride ion concentration in tablets and solutions containing sodium fluoride. The method has been subjected to collaborative study. Eight samples consisting of 2 authentic fluoride solutions, 2 commercial fluoride solutions, and 4 commercial fluoride tablets were sent to each of 11 collaborators together with a copy of the method. Single assays on the authentic fluoride solutions known to contain 1 mg F/5 mL were performed with average recoveries of 99.5 and 99.6% and relative coefficients of variation (CV) of 2.11 and 1.91%, respectively. Single assays of 2 commercial fluoride solutions declared at 1 mg F/5 mL gave mean values of 0.994 and 0.990 mg and relative CV values of 1.88 and 2.36%, respectively. Single assays of 2 commercial fluoride tablet preparations declared at 0.5 mg F gave mean values of 0.485 and 0.478 mg and relative CV values of 3.12 and 3.71 %, respectively. Single assays of 2 commercial fluoride tablet preparations declared at 1 mg F gave mean values of 0.991 and 0.981 mg and relative CV values of 2.99 and 2.85%, respectively. The method has been adopted official first action.

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Determination of Biuret in Urea and Mixed Fertilizers by Cupric Ion Selective Electrode

Journal of AOAC INTERNATIONAL ◽

10.1093/jaoac/69.1.119 ◽

1986 ◽

Vol 69 (1) ◽

pp. 119-122

Author(s):

Luis F Corominas ◽

Roberto A Navarro ◽

Pedro Rojas ◽

José L Cruz

Keyword(s):

Atomic Absorption ◽

Copper Complex ◽

Confidence Level ◽

Collaborative Study ◽

Ion Selective Electrode ◽

Selective Electrode ◽

Cupric Ion ◽

Excess Copper ◽

Aas Method

Abstract A method for determining biuret in urea and mixed fertilizers by using a cupric ion selective electrode (CISE) has been developed to take advantage of the simplicity of the apparatus. The method is based on the same principle as the atomic absorption spectrophotometric (AAS) method, 2.091-2.093: formation of a biuret-copper complex, elimination of excess copper, and determination of complexed copper. However, some changes were needed to eliminate starch and alcohol interferences. The method was tested for ruggedness and then compared with the AAS method for 4 fertilizer samples. Averages and variances were equivalent at the 99% confidence level according to t- and F-tests. A collaborative study is recommended to compare behavior of both methods in different laboratories.

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Comparison of HgO and CuS04 as Digestion Catalysts in Manual Kjeldahl Determination of Crude Protein in Animal Feeds: Collaborative Study

Journal of AOAC INTERNATIONAL ◽

10.1093/jaoac/67.5.869 ◽

1984 ◽

Vol 67 (5) ◽

pp. 869-877 ◽

Cited By ~ 1

Author(s):

Peter F Kane ◽

◽

A Altemeier ◽

L L Austin ◽

C V Beggs ◽

...

Keyword(s):

Crude Protein ◽

Animal Feed ◽

Collaborative Study ◽

Matched Pairs ◽

Animal Feeds ◽

Kjeldahl Method ◽

Environmental Considerations ◽

Standard Deviations ◽

Digestion Step

Abstract The official AOAC manual Kjeldahl method for determining crude protein in animal feeds, 7.015, uses HgO as a catalyst in the digestion step. Because of environmental considerations, there is considerable interest in alternative catalysts. A collaborative study compares the official HgO-catalyzed method and an alternative using CuS04. Fifty-four samples consisting of blind duplicates of closely matched pairs, representing a range of animal feed materials and 2 standard materials, were analyzed once by each method. Results were returned by 22 laboratories. Means and standard deviations between methods were comparable. The CuS04-catalyzed method has been adopted official first action.

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Titration of sulphates and lead using lead ion selective electrode

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19810368 ◽

1981 ◽

Vol 46 (2) ◽

pp. 368-376 ◽

Cited By ~ 4

Author(s):

Josef Veselý

Keyword(s):

Ionic Strength ◽

Electrode Surface ◽

Salt Content ◽

Ion Selective Electrode ◽

Lead Ion ◽

Selective Electrode ◽

Limit Of Determination ◽

Total Salt Content ◽

Automatic Titration

Titration of sulphates with lead perchlorate employing lead ion selective electrode indication was studied using additions of various organic solvents at different pH' and ionic strength values. As the optimum emerged systems with 60-70% 1,4-dioxane, pH' 5.3-5.6. After dehydration with sodium hydroxide, dioxane must be freed from the electrode surface-oxidizing impurities by their reduction with sodium metal and subsequent distillation. The method was applied to determination of sulphates in mountain spring waters. Units of ppm can be determined; the limit of determination, however, depends considerably on the content of dioxane, total salt content in the sample, and speed of the semi-automatic titration. Lead can be determined with EDTA in concentrations down to c(Pb2+) = 5 . 10-6 mol l-1.

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Using MoS2/Fe3O4 as Ion-Electron Transduction Layer to Manufacture All-Solid-State Ion-Selective Electrode for Determination of Serum Potassium

Chemosensors ◽

10.3390/chemosensors9070155 ◽

2021 ◽

Vol 9 (7) ◽

pp. 155

Author(s):

Yan Su ◽

Ting Liu ◽

Caiqiao Song ◽

Aiqiao Fan ◽

Nan Zhu ◽

...

Keyword(s):

High Performance ◽

Accurate Determination ◽

Water Layer ◽

Ion Selective Electrode ◽

Potential Response ◽

Selective Electrode ◽

Response Measurement ◽

Long Term Stability

As an essential electrolyte for the human body, the potassium ion (K+) plays many physiological roles in living cells, so the rapid and accurate determination of serum K+ is of great significance. In this work, we developed a solid-contact ion-selective electrode (SC-ISE) using MoS2/Fe3O4 composites as the ion-to-electron transducer to determine serum K+. The potential response measurement of MoS2/Fe3O4/K+-ISE shows a Nernst response by a slope of 55.2 ± 0.1 mV/decade and a low detection limit of 6.3 × 10−6 M. The proposed electrode exhibits outstanding resistance to the interference of O2, CO2, light, and water layer formation. Remarkably, it also presents a high performance in potential reproducibility and long-term stability.

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Collaborative Study of the Spectrophotometric Determination of Procainamide Hydrochloride

Journal of AOAC INTERNATIONAL ◽

10.1093/jaoac/59.4.807 ◽

1976 ◽

Vol 59 (4) ◽

pp. 807-810

Author(s):

Jeffrey C Hamm

Keyword(s):

Sodium Hydroxide ◽

Acid Medium ◽

Spectrophotometric Determination ◽

Spectrophotometric Method ◽

Collaborative Study ◽

Dosage Forms ◽

Standard Deviations

Abstract The USP analysis for procainamide HCl is titrimetric and relatively nonspecific, capsule and tablet dyes may interfere, and the method is not applicable to coated tablets. In the spectrophotofluorometric method the sample deteriorates when exposed to a xenon source. In the ultraviolet spectrophotometric method reported here, the sample is dispersed in acid medium, possible interferences are extracted in chloroform, base is added, procainamide is extracted in chloroform, the residue is dissolved in sodium hydroxide, and the compound is measured by absorption at 272 nm and comparison with a standard. Recoveries of standards added to capsule, tablet, and injection composites ranged from 99.3 to 102%. Twelve collaborators reported duplicate assay results for all 3 dosage forms with per cent standard deviations for 5 samples ranging from 1.01 to 1.27%. The method has been adopted as official first action.

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