Potentiometric microdetermination of aluminium in organic compounds after combustion in a modified oxygen flask

The microdetermination of aluminium in organic compounds by oxygen flask combustion, a simultaneous fusioncombustion procedure was developed, in which the sample in a mixture with KHSO₄ is burnt in a modified oxygen flask under suitable conditions so that the alumina formed is immediately converted into the corresponding water-soluble sulfate. 2.4 ml of 6M HCl are used as absorption solution, in which the combustion residue is completely dissolved by boiling. The solution is then transferred to a titration cell, neutralized with NaOH in the presence of methyl red, and the Al(III) is finally determined in a buffered 40% (V/V) dioxane solution by potentiometric titration with 0.1 M NaF. The results obtained were accurate within ±0.13%; the recoveries of Al are in the range of 99.00 to 99.90%; the standard deviation amounts to 0.06%. The potentiometric titration of Al(III) with fluoride as well as the conditions of the oxygen flask combustion of organic aluminium compounds are discussed.     

Evaluation of biological sample mineralisation methods for the determination of fluorine by graphite furnace molecular absorption spectrometry

Various mineralisation methods were evaluated as means of treating different liquid and solid biological samples for the determination of fluorine by the formation of aluminium monofluoride in an electrothermal graphite furnace and molecular absorption spectrometry (AIF-MAS). Simple sample dilution and the use of 0.01 M Al3+ + 0.01 M Sr2+ solution as a matrix modifier are sufficient to determine the fluorine content in most liquid samples, although some require the addition of 0.3 M ammonium nitrate to the matrix modifier solution in order to diminish background absorbance. In solid samples, treatment methods routinely used with fluoride ion-selective electrodes such as microdiffusion, furnace ashing - microdiffusion and oxygen flask combustion, were tested for compatibility with AIF-MAS. The results were compared with those obtained with a fluoride ion-selective electrode. The proposed mineralisation methods were checked for applicability to different plants, foodstuffs and other biological materials. Some of the methods gave an over-all precision of better than 10%, which is often acceptable, and all methods gave recoveries above 80%. Differences between labile + ionic fluoride and total fluorine can be established by sample treatment.     

Determination of fluorine in organic and organometallic compounds

Summary A method is described for the determination of fluorine in organic and organo-metallic compounds. Following oxygen-filled flask combustion in a silica flask, an aliquot of the absorbent solution is analysed for fluoride by a standard addition technique utilising a fluoride selective electrode.

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Fluorbestimmung in organischen und metallorganischen Verbindungen

Zusammenfassung Nach Verbrennung im sauerstoff-gefüllten Quarzkolben wird ein gemessener Teil der Absorptionslösung nach der Standard-Zusatztechnik mit Hilfe einer fluorspezifischen Elektrode analysiert.

     

Titrimetric determination of organofluorine using Arsenazo I as indicator

Summary Some improvements of the titrimetrio method for determining fluorine in organic compounds are described. The modifications involve:(a) introduction of a combustion aid for the electrically heated flask combustion to insure complete conversion of fluorine to hydrogen fluoride, (b) employment of a glycine-perchlorate buffer to maintain a consistent stoichiometric titration, and (c) adaptation of an automatic titrimeter for photometric titration to simplify the detection of the end point. It is also suggested that a linear equation be derived from the calibration data in order to calculate the fluorine content.

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Zusammenfassung Einige Verbesserungen der maßanalytischen Bestimmungsmethode für Fluor in organischen Substanzen wurden beschrieben, nämlich: a) Einführung eines Zusatzreagens zur Erzielung einer vollständigen Überführung in Fluorwasserstoff bei der elektrischen Verbrennung im verschlossenen Kolben; b) Verwendung einer Pufferlösung von Glycin und Perchlorat zur Gewährleistung einer stöchiometrischen Titration; c) Anpassung eines automatischen Titriergerätes für photometrische Titrationen zwecks besserer Wahrnehmung des Endpunktes. Außerdem wird empfohlen, zur Berechnung des Fluorgehaltes eine lineare Gleichung zu verwenden.

     

Determination of fluorine in boron-containing materials with a fluoride sensitive electrode

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.

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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.

     

Microdetermination of fluorine in organic compounds containing phosphorus and in hexafluorophosphates

Summary A method for the microdetermination of fluorine in organic compounds containing phosphorus is described. After combustion in a Vycor flask, the species containing phosphorus are oxidized to orthophosphate with alkaline hypobromite. Phosphate is adsorbed on zinc oxide which need not be removed prior to titration of the fluoride. Fluoride is titrated potentiometrically with 0.02M lanthanum(III) in 50% ethanol solution at p_H 5–7. A fluoride ion-specific indicator electrode and a calomel reference electrode are used in conjunction with an expanded-scale p_H meter to monitor the emf. This method can also be used for the determination of total fluorine in inorganic hexafluorophosphates. For the more stable compounds such as potassium hexafluorophosphate, a combustion aid (paraffin) must be added to promote combustion.

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Zusammenfassung Ein Verfahren zur Mikrobestimmung von Fluor in organischen, phosphorhältigen Verbindungen wurde beschrieben. Nach der Verbrennung in sauerstoffgefüllten Kolben werden die phosphorhältigen Produkte mit Alkalihypobromit zu Orthophosphat oxydiert. Dieses wird an Zinkoxid adsorbiert, das vor der Fluoridtitration nicht entfernt werden muß. Die Titration erfolgt potentiometrisch mit 0,02-m Lanthan(III)-lösung in 50%igem Äthanol bei p_H 5–7. Eine fluoridspezifische Indikatorelektrode und eine Kalomel-Bezugselektrode werden in Verbindung mit einem p_H-Meter mit gedehnter Skala zur Messung verwendet.Das Verfahren ist auch zur Fluorbestimmung in anorganischen Hexafluorphosphaten geeignet. Für die Analyse beständiger Verbindungen wie z. B. Kaliumhexafluorophosphat verwendet man Paraffin als Verbrennungszusatz.

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Work performed under the auspices of the U. S. Atomic Energy Commission.     

Determination of total fluorine in blood at trace concentration levels by the Wickbold decomposition method with direct potentiometric detection

The Wickbold decomposition method in combination with differential potentiometric detection via fluoride ion-selective electrode has been applied to analysis of total fluorine in biological matrices. The performance of the method has been evaluated for determination of total fluorine in rat blood. Total mineralization of the biological sample is achieved by combustion of the sample in oxygen/hydrogen flame and subsequent absorption of the resulting fluoride in aqueous absorption medium. The fluoride is then quantified by highly selective automated differential static potentiometry with fluoride ion-selective electrode. Total fluorine determination has been evaluated in terms of sample carryover, reproducibility, precision, as well as feasibility to routine analysis of alternative biological matrices. Our results indicate that, up to 100 ppm fluorine in blood, the method does not suffer from sample carryover. Limits of quantitation of 0.5 ppm and limits of detection of 0.24 ppm fluorine in 0.5 g blood samples were achieved by elimination of inherent limitations of fluoride ion-selective electrode detection via automated differential static potentiometric measurements. The Wickbold decomposition method was found to be suitable for routine total fluorine determination in blood samples despite its relatively low throughput and high operator skill requirements.     

Störende Wirkung des Fluors bei der Mikrobestimmung organisch gebundenen Schwefels nach Fritz-Yamamura

Zusammenfassung Die störende Wirkung des Fluors bei der Sulfattitration nach Fritz und Yamamura wurde eingehend untersucht. Die Höhe des Blindwertes hängt offenbar von der Menge Flußsäure ab, die bei der Verbrennung im geschlossenen Kolben entsteht, ohne dieser jedoch proportional zu sein.

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The interfering effect of fluorine in the microdetermination of organically bound sulfur according to Fritz-Yamamura

Summary The interfering effect of fluorine in the sulfate titration according to Fritz and Yamamura was investigated in detail. The size of the blank value is clearly dependent on the amount of hydrogen fluoride formed by combustion in the closed flask, though it is not proportional to it.

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Der Fa. Zambon S. p. A. Farmaceutici, Bresso-Milano, sind wir für die freundliche Überlassung von schwefel- und fluorhaltigen Proben zu aufrichtigem Dank verpflichtet.     

A titrimetric method for estimation of fluorine in organic compounds

A simple and rapid titrimetric method for estimation of fluorine in organic compounds and fluoropolymers is reported. It involves combustion of the sample in oxygen, absorption of the combustion products in an aqueous solution of Ce(III) nitrate and glycerol, containing hexamethylenetetramine, and finally titration with EDTA, with Xylenol Orange and Methylene Blue as screened indicator.     

Simultaneous ultramicrodetermination of heterogeneous halogens in organic compounds

The simultaneous ultramicrodetermination of heterogeneous halogens in organic compounds was carried out by the potentiometric titration with 0.002 M silver nitrate after the sample was decomposed by the flask combustion method. In examination of the titration, it was found that clear potential break at the end point was obtained by controlling the delivery speed of the titrant at 0.2 ml/min or slower and the temperature of the solution to be titrated at ca. 10 °C when chloride ion is present. The error due to coprecipitation during the titration and the effect of the mole ratio of heterogeneous halide ions in the sample solution was examined and discussed. The analysis of organic halogen compounds resulted in an error of within 0.4% and standard deviation of less than 0.25%.     

The rapid determination of iodine in organic substances

A simple and rapid method for determination of iodine in highly iodized organic substances is described. The method involves oxygen flask combustion of the sample to be analyzed, formation of iodine in a molecular form, and use of a special multicomponent absorption solution containing sodium thiosulfate, phosphate buffer, pH 7.1–7.2, and starch. The quantity of absorbed iodine is determined by iodometric titration of the excess sodium thiosulfate in the absorption solution. The method affords a drastic reduction in the total length of analysis. The relative error of determination is not greater than 1%.     

Determination of sulfur in organic compounds using a barium-selective electrode

A procedure was developed for determining sulfur (>1.5 abs %) in sulfur-containing organic compounds. The procedure was based on the combustion of a sample portion in a flask filled with oxygen followed by the potentiometric titration of sulfate ions with barium nitrate in a water-acetone solution. In distinction from analogous procedures, halogens and metals contained in the analyzed compound did not interfere with the determination of sulfur. The error of determination was below 3 rel %.     

Simultaneous microdetermination of iodine and sulfur in organic compounds

A simple and rapid method for the simultaneous microdetermination of iodine and sulfur in organic compounds is described. The procedure utilizes the Schöniger flask method for the combustion, the iodide ions titration with 0.01 N mercuric perchlorate solution and diphenylcarbazone as indicator and the sulfate ions titration with 0.01 M barium perchlorate solution and dimethylsulfonazo III as indicator. The results obtained are in good agreement with calculated values.     

碱熔-蒸馏-滴定法测定萤石中的氟化钙含量

采用碱熔-蒸馏-滴定法测萤石中氟含量,计算得到氟化钙含量.萤石试样首先用碳酸钠碱熔消解,然后经硫酸-水蒸气蒸馏分离氟,以茜素磺酸钠作指示剂,用硝酸钍溶液滴定测出其中氟含量,并计算得到氟化钙含量.利用X射线衍射光谱(X RD)法验证了萤石中氟的存在形式,并通过实验确定了碳酸钠使用量、硫酸溶液加入量、蒸馏温度和蒸馏时间等的...     

Decimilligram-scale determination of sulfur in organic compounds

A simple and rapid method for the decimilligram-scale determination of sulfur in organic compounds is described. The procedure utilizes the Schöniger flask method for the combustion and the sulfate-ion titration, with 0.01 M barium perchlorate solution and dimethylsulfonazo III as indicator. The results obtained are exact and precise.     

Determination of sulfate and sulfur in inorganic and organic materials

Sulfate is determined by titration with lead nitrate solution in aqueous acetone solutions buffered with nitric acid-pyridine, in presence of dithizone indicator. Sulfate is titrated directly or after separation from interfering ions and other materials on a column containing aluminum oxide and cation-exchange resin. The titration and separation are also applied to determination of sulfur in organic compounds after oxygen flask combustion. Details of the methods are fully discussed.     

Simplification of the mercurimetric procedure for organohalogen determination

The mercurimetric method for organohalogen determination described in 1959 can be further simplified by omitting the boiling process for removal of hydrogen peroxide after combustion of the sample in the oxygen flask. Hydrogen peroxide does not interfere in the mercurimetric titration. Its presence did show certain advantages in the work of other investigators as well as in this present study.     

Potentiometric microdetermination of cadmium in organic compounds after oxygen flask combustion

The sample is burnt in an oxygen flask and the combustion products are absorbed in lM HNO₃. After removal of interfering gases by boiling, the solution is transferred to the titration cell and neutralized with NaOH in the presence of methyl red; Cd(II) is finally titrated potentiometrically in a buffered 50% ethanolic medium with 0.01M sodium diethyldithiocarbamate in 50% ethanol. A silver/sulphide ion-selective electrode and a double junction reference electrode containing a 10% KNO₃ solution in 26% ethanol in the outer compartment are used in combination with a Titroprocessor to detect the end point. The results obtained are very accurate and reproducible: the maximum error does not exceed 0.09%, the recovery of cadmium is in the range 99.67 to 99.95% and the rel. standard deviation is 0.05%. The potentiometric titration with diethyldithiocarbamate, which is useful to determine small Cd(II) amounts down to 30g (2g ml^–1), as well as the oxygen flask combustion of organic cadmium compounds are discussed.     

防龋健齿口胶中微量氟的测定

采用氧瓶燃烧法，利用氟离子选择电极测定了茶叶及防龋健齿口胶中氟离子的含量，并做了回收率实验，实验证明，本法准确度高，回收率好，简便易行。     

Application of the Combustion Method in a Closed Flask to the Lead Determination in Atmospheric Aerosols

Abstract

The destruction of the filter for metal determination in atmospheric aerosols is an important step in the analysis. Nowadays the decomposition of this kind of sample has not been completely solved, so it is interesting to study new methods for filter sample attack. In the present work the application of the combustion method in a closed flask for mixed cellulose esters filter decomposition for lead determination is proposed. For this purpose optimum operating conditions as stopper flask design, sample size, flask volume, shaking time and volume and concentration of absorbing solution are established, and accuracy and precision of the proposed method using AAS for the measurements is given. The results obtained by the closed flask combustion are compared with those found by wet attack with HNO₃. The method proposed is rapid, has low reagent contamination and no loss of lead by volatilization or by amalgamation occurs. This method shows an accuracy and a precision in good agreement with the standard method.