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Summary The fluoride-ion selective micro-determination of fluorine in organic materials after closed flask combustion is an established technique. Interferences, due to complexation of the fluoride ion can occur, if the sample contains boron or fluorborate ion. This paper describes a method that avoids complexation of fluoride by combustion in a hydrogen-oxygen flame and absorption of the resulting H2F2 in alkali hydroxide solution. By this method, samples can be analyzed for fluorine without interference by boron. Some results of the analysis of pharmaceutical materials are given.
Zusammenfassung Die Mikrobestimmung von Fluor in organischem Material nach Kolbenverbrennung mit Hilfe einer fluoridspezifischen Elektrode ist eine eingeführte Methode. Störungen infolge Komplexierung des Fluoridions können auftreten, wenn die Probe Bor oder Fluorborat enthält. Die vorliegende Arbeit beschreibt eine Methode, um diese Komplexbildung durch Verbrennung in der Knallgasflamme und Absorption des H2F2 in Alkalilauge zu vermeiden. Einige Analysenergebnisse pharmazeutischen Materials werden angeführt.相似文献
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The application of the fluoride-ion activity electrode to the determination of fluoride in various samples has been studied. Samples are decomposed by fusion and the fluoride concentration is determined by a standard-addition or a direct method. The standard-addition method is unsuitable, owing to a positive bias. The direct method, however, is rapid, accurate and precise. The fluoride content of exploration ores, fluorspar, opal glass, phosphate rock and various production samples, has been successfully determined. The success of the direct method depends on the effectiveness of the system used to buffer pH and ionic strength and complex possible interferences (Al(3+), Ca(2+), Fe(3+)). The effect of interferences has been studied and found to be minimal. The procedures are rapid and accurate and may be substituted for the traditional Willard and Winter or pyro hydrolysis methods, with considerable saving of time. 相似文献
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Berit Eyde 《Fresenius' Journal of Analytical Chemistry》1985,320(1):41-44
Summary A method is described for the determination of acid and water soluble fluoride in some commercial fertilizers. The ground samples are stirred with water or with hydrochloric acid of different concentrations, filtered, citrate added as complexing agent, and then measured with an ion-selective electrode. With most of the investigated samples it was seen that the more concentrated the acid (up to 1.00 M HCl) the more fluoride was found in the solution, and this was supposed to be the same as the total amount.The relative standard deviation was usually between 0.5 and 1.5%. The recovery of added fluoride to some samples was between 97 and 100%. The results from this method were compared with the results from a reference method, and there was good correlation between them.
Bestimmung von Fluorid in Düngemitteln mit Hilfe der ionen-selektiven Elektrode
Zusammenfassung Ein Verfahren wird beschrieben zur Bestimmung des säure- und wasserlöslichen Fluorids in einigen handelsüblichen Düngemitteln. Die gemahlenen Proben werden mit Wasser oder Salzsäure verschiedener Konzentration gerührt, filtriert, mit Citrat als Komplexbildner versetzt und dann mit Hilfe einer ionen-selektiven Elektrode gemessen. Bei den meisten Proben ergab sich, daß bei höherer Säurekonzentration (bis 1,0 M HCl) mehr Fluorid gefunden wurde, was dann dem Gesamtfluorid entsprach.Die relative Standardabweichung lag im allgemeinen zwischen 0,5 und 1,5%. Die Wiederfindung an zugesetztem Fluorid lag zwischen 97 und 100%. Die Ergebnisse wurden mit den nach einer Referenzmethode erhaltenen verglichen, und es ergab sich eine gute Übereinstimmung.相似文献
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Thorsten Eriksson 《Analytica chimica acta》1973,65(2):417-424
It is shown that the total amount of hydrofluoric acid in strong hydrochloric or nitric acid solutions with varying acidity can be determined directly with two ion-selective electrodes. Equations were derived and calibration procedures for both electrodes were developed. The influence of liquid junctions at the reference electrodes was investigated and it was possible to simplify the equations by the use of a suitable bridge solution. The formation constant of the dimer (HF)2 was redetermined and found to be 0.26. 相似文献
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R. M. Sawant G. H. Rizvi N. K. Chaudhuri S. K. Patil 《Journal of Radioanalytical and Nuclear Chemistry》1985,89(2):373-378
Fluoride complexing of Np(V) has been studied using fluoride ion selective electrode (F-ISE). Free fluoride ion concentrations in the presence of Np(V) were measured at 0.1 and 1.0M ionic strength. The data were used to calculate the stability constant of the fluoride complex of Np(V) and the values obtained are reported here. 相似文献
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Determination of fluoride in hydrometallurgical zinc-plant processing products and solutions with a fluoride-ion electrode is described. Various types of buffers were tested, to find a suitable common buffer for use in analysis of all types of substances generated at the zinc plant. The method involves decomposition of samples either by fusion with sodium hydroxide or by leaching with perchloric acid to bring fluoride into solution. The fluoride concentration is measured directly with a fluoride-specific electrode. In standard addition tests 100% recovery was obtained when a citric acid/sodium nitrate buffer was used. Validation tests gave satisfactory results. 相似文献
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The most effective conditions for masking aluminium in the determination of mug/1. levels of fluoride in water by ion-selective electrode potentiometry after co-precipitation with aluminium phosphate have been re-examined. The effectiveness of citrate for masking aluminium increases with pH, and up to 1.5 x 10(-2)M aluminium can be masked quantitatively at pH 8.5. Fluoride (5-100 mug in 500 ml of sample solution) is quantitatively co-precipitated at pH 4.7 with approximately 90 mg of aluminium phosphate. After dissolution of the precipitate and adjustment of the solution to pH 8.5 with TISAB, the fluoride content can be measured with a fluoride ISE. The method is simple and rapid, and is suitable for the determination of trace amounts of fluoride in various water samples. 相似文献
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M. S. Turaeva I. A. Pegova M. M. Urchukova I. V. Murin 《Russian Journal of Electrochemistry》2007,43(4):418-427
The voltammetry method with a linear potential scan is used for investigating the effect the electrode material (Ni, Co, electrodes on the basis of cobalt oxides modified with carbon) exerts on the reduction of gaseous oxygen at interfaces solid fluoride-conducting electrode LaF3:Eu2+/electrode, O2, and conjugated processes. Properties of the modified electrodes are characterized by the impedance spectroscopy, scanning electron microscopy, and x-ray photoelectron spectroscopy methods. The oxygen reaction is irreversible at the LaF3:Eu2+|Ni (or Co) interfaces. At the interface of LaF3:Eu2+ with modified electrodes Co (C n at %), where n = 5 and 9, mobile forms of oxygen are reversible and the reduction of gaseous and chemisorbed oxygen is controlled by diffusion with different effective kinetic parameters. 相似文献
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The accuracy, precision, and reproducibility of a rapid method for determination of fluoride in wine, using a fluoride selective ion electrode, were established by a collaborative study involving 12 laboratories, 5 in Europe and 7 in the United States. The laboratories assayed 6 Youden pairs of fluoride-fortified, red and white wine samples with fluoride concentrations ranging from 0.2 to 3.0 mg/L. The relative standard deviations of repeatability ranged from 1.94 to 4.88%; relative standard deviations of reproducibility ranged from 4.15 to 18.40%. HORRAT values ranged from 0.30 to 0.97. The average recovery was 99.97%. Based on the statistical results of this collaborative study, the Study Director recommends that this method be adopted First Action. 相似文献
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A rapid and accurate method for the determination of the total sulphur content of soil or plant material is described. The sample is heated with sodium bicarbonate and silver oxide at 550° for 3h, and the sulphur content of the whole residue is reduced to hydrogen sulphide and determined as methylene blue. The results compare favourably with those of other methods.In routine use, at least 30 analyses may be completed in a day. 相似文献
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Berit Eyde Kjuus 《Fresenius' Journal of Analytical Chemistry》1986,323(3):264-265
Summary When measuring nitrate in agricultural material (ensilage, dung etc.) extracted with copper sulphate solution with the nitrate selective electrode some of the samples were difficult to measure due to unstable readings and a gradually change in the calibration curve. These problems could easily be reduced by simply diluting the samples before measuring. To the diluted samples standards were added before measurement to keep the readings in the linear part of the calibration curve. In addition this dilution will increase the life time of the electrode.
Nitratbestimmung in landwirtschaftlichem Material mit Hilfe der Nitrat-selektiven Elektrode
Zusammenfassung Bei der Messung von Nitrat in landwirtschaftlichem Material (Silage, Dung u.a.) mit Hilfe der Nitrat-selektiven Elektrode nach Extraktion mit Kupfersulfatlösung ergaben sich bei einigen Proben Schwierigkeiten wegen instabiler Anzeigen und allmählichen Veränderungen der Eichkurve. Diese Probleme konnten durch einfache Verdünnung vor der Messung reduziert werden. Zu den verdünnten Proben wurden vor der Messung Standards zugesetzt, um die Ablesungen innerhalb des linearen Teils der Eichkurve zu halten. Zusätzlich wird durch die Verdünnung die Lebensdauer der Elektroden erhöht.相似文献
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A method is described for determining 10-5–10-4M fluoride in a variety of solutions potentiometrically with a fluoridc-specific electrode, by a standard addition method. Any change of ionic strength or the nature of the solution that might alter activity coefficients or junction potentials is minimized. The relationship between potential and fluoride concentration thus follows the Nernst equation, and the unknown concentration can be calculated. Experimental data are given for solutions of sodium choride, sodium nitrate, acidified sodium silicate and sodium hydroxide, lithium chloride, and phosphoric acid. Metal ions (e.g., Al3+, UO22+, Fe3+, Th4+) that interfere by forming complexes with fluoride can be precomplexed with phosphoric acid. The relative error is estimated at 10%, and the relative standard deviation is less than 5% over the concentration range 10-5–10-4M fluoride. 相似文献
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R. M. Sawant N. K. Chaudhuri G. H. Rizvi S. K. Patil 《Journal of Radioanalytical and Nuclear Chemistry》1985,91(1):41-58
Complex formation between actinide(VI) and fluoride ions in aqueous solutions has been investigated using a fluoride ion selective electrode (F-ISE). As fairly high acidity was used to suppress hydrolysis of the actinide(VI) ions, significant liquid junction potentials (Ej) existed in the systems. An iterative procedure was developed for computing free hydrogen ion concentration [H+], as it could not be measured directly, using data obtained with F-ISE. Ej values were estimated from known [H+] and the stability constants of fluoride complexes of actinide(VI) ions were calculated following KING and GALLAGHER's method using a computer program. The stability constants were found to follow the order U(VI)>Np(VI)>Pu(VI). 相似文献
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Jacobus F. Staden 《Fresenius' Journal of Analytical Chemistry》1988,332(2):157-161
Summary The incorporation, behaviour and suitability of a simple and cheap home-made coated tubular solid-state silver(I)-selective electrode into the conduits of a flow-injection system is described. With 30 l samples the flow-injection flow-through electrode system covers a working range up to 5000 mg/l. The system is suitable for the determination of silver(I) in diluted plant solutions from photographic material at a sample frequency of about 80 h–1. This procedure is also characterized by excellent reproducibility (<0.24% for 0.06–76 g/l silver in the original plant solution). The results obtained agree well with results by a standard atomic absorption spectrometric method.
Bestimmung von Silber in photographischem Material mit Hilfe der Fließinjektionsanalyse mit einer überzogenen Feststoff-Silbersulfid-ionensensitiven Röhren-Elektrode als Detektor相似文献
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A modification of the potentiometric determination of fluoride has been developed, which allows use of aqueous fluoride standards in analysis of lead or zinc concentrates, instead of the need to use matrix-matching or standard additions. 相似文献