Enthalpimetric determination of total lead in gasoline

A method is descubed for the determination of lead alkyl additives in gasoline by direct injection enthalpimetry. The method is a single step process, iodine monochloride solution is injected into a sample of the gasoline diluted with an equal volume ofo-xylene. The system can be arranged to gave a direct reading of the concentration of the permitted lead alkyls for several concentration ranges. Once calibrated the proposed method can be operated by semi-skilled workers. The precision and accuracy are within industrial limits. The main advantages of the method are those of low cost and low time of analysis.     

Enthalpimetric determination of the iodine value of some edible oils and fats

A simple, rapid and accurate direct injection enthalpimetric (DIE) method has been developed for the determination of the iodine value of some commercial edible oils. A significant heat pulse of halogen addition reaction of the double bonds of unsaturated fatty acid esters in the oils is produced by injecting a solution of iodine monochloride into the sample solutions. The method is calibrated against real samples and the standard compounds (oleic, linoleic and linolenic acids) whose iodine values have been determined by a standard method. Once calibrated, the proposed method can be operated routinely by semi-skilled personnel. The method is sensitive and give results as acceptable as those obtained by standard methods. The main advantages of the method are those of time and cost of analysis and the potential of the enthalpimetric method for automation.

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Zusammenfassung Zur Ermittlung der Jodzahl von einigen im Handel befindlichen Speiseölen wurde ein einfaches, schnelles und genaues Enthalpimetrieverfahren mit Direkteinspritzung (DIE) entwickelt. Mittels Einspritzung einer Jodmonochloridlösung in die Probenlösung wird wegen der Halogenadditionsreaktion an den Doppelbindungen der ungesÄttigten FettsÄureester ein signifikanter WÄrmeimpuls erzeugt. Die Methode wird anhand tatsÄchlicher Proben und Standardproben (ölsÄure, LinolsÄure, LinolensÄure) kalibriert, deren Jodzahl in Standardverfahren bestimmt wurde. Nach einmaliger Kalibration kann das Verfahren auch von angelerntem Personal routinemÄ\ig durchgeführt werden. Das Verfahren besitzt eine ausreichende Empfindlichkeit und liefert Ergebnisse, die genauso akzeptabel sind, wie die in Standardverfahren erhaltenen Ergebnisse. Die Hauptvorteile dieser Methode bestehen in Zeit- und Kosteneinsparung bei der Analyse sowie in der Möglichkeit, das enthalpimetrische Verfahren automatisieren zu können.

     

Enthalpimetric determination of sulphide and thiosulphate by the catalysis of the iodine-azide reaction

The enthalpimetric determination of sulphide and thiosulphate, in the presence and absence of Zn²⁺ and Cd²⁺, making use of the catalysis of the iodine-azide reaction is studied. An excess of the cations avoids losses of sulphide as H₂S and, when cadmium is used, a 30% enhancement of the sensitivity is observed in the determination of sulphide. On the other hand, both cations depress the analytical response produced by thiosulphate, but iodide can be used as an enhancement agent. Limits of detection of 0.1 and 0.3 ppm are obtained for sulphide and thiosulphate, respectively, and linear dynamic ranges comprise about two orders of magnitude.     

Enthalpimetric assay of cerium-iron alloys

Direct injection enthalpimetric determination of cerium/IV/ and iron/III/ were performed sequentially in the same solution of ferro-cerium alloys using potassium iodide and sodium thiosulphate solutions.     

Enthalpimetric and thermometric determination of some nitrogen containing bases and some physiologically active alkaloids

Summary The enthalpimetric determination of a series of bases by using the reaction of the bases and sodium tetraphenylboron is described. The accuracy of the method is analytically acceptable, over the range 3×10^–5 moles to 7.5×10^–4 moles. The upper limit is determined by the bulk of the precipitate.Dosage forms of some physiologically active alkaloids contain more than the upper limit of analyte. Yet, preliminary investigations using silicotungstic acid indicate that this is suitable for thermometric titrations.

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Enthalpimetrische und thermometrische Bestimmung stickstoffhaltiger Basen und physiologisch aktiver Alkaloide

Zusammenfassung Die enthalpimetrische Bestimmung einiger N-haltiger Basen erfolgte aufgrund der Reaktion mit Natriumtetraphenyloborat. Die Genauigkeit ist im Bereich von 3 · 10^–5-7,5 · 10^–4 Mol befriedigend. Eine obere Grenze der Anwendbarkeit ergibt sich aus der Menge des anfallenden Niederschlags. Diese wird bei der Bestimmung von Formulierungen einiger physiologisch aktiver Alkaloide überschritten. Jedoch ist in diesem Fall eine thermometrische Titration mit Hilfe von Silicowolframsäure möglich.

Lecture presented at Euroanalysis I Conference, 28. 8.–1. 9. 1972 in Heidelberg, Germany.     

Enthalpimetric determinations with sodium hypobromit

The applicability of sodium hypobromite as a reagent in enthalpimetric determinations of various organic and inorganic compounds is reviewed. Using this method it is possible to determine various oxidizable nitrogen and sulphur compounds, e.g. ammonium salts, urea, -amino acids, sulphides, sulphites, thiosulphates, organic compounds with sulphidic sulphur, aromatic amines, mono- and polyphenols, and other compounds. Determinations are sufficiently precise and sensitive. The enthalpy changes of these reactions are approximately 10² to 10³ kJ mole^–1. Suggested determinations are advantageous due to their simplicity, quickness and possible automatization of measurements.

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Zusammenfassung Die Autoren geben einen Überblick zur Anwendung von Natriumhypobromit als Reagenz bei den enthalpimetrischen Bestimmungen verschiedener organischer und anorganischer Verbindungen. Der Einsatz dieser Methode ermöglicht die Bestimmung verschiedener oxidierbarer Stickstoff- und Schwefelverbindungen, wie z.B. Ammoniumsalze, Karbamid, -Aminosäuren, Sulfide, Sulfite, Thiosulfate, organische Verbindungen mit Sulfidschwefel, aromatische Amine, ein- und mehrwertige Phenole und andere Verbindungen. Die Bestimmungen sind genügend genau und empfindlich. Die Enthalpie-Änderungen dieser Reaktionen liegen in der Größenordnung von 10² is 10³ kJ Mol^–1. Die vorgeschlagenen Bestimmungen sind wegen ihrer Einfachheit, Schnelligkeit und der Möglichkeit der Automatisierung der Messungen vorteilhaft.

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Résumé Les auteurs examinent l'emploi de l'hypobromite de sodium comme réactif pour le dosage enthalpimétrique de divers composés organiques et inorganiques. Par cette méthode il est possible de doser différents composés azotés et sulfurés, par ex. les sels d'ammonium, l'urée, les -amino-acides, les sulfures, les sulfites, les thiosulfates, les composés organiques sulfurés, les amines aromatiques, les phénols mono et polyvalents et d'autres composés. Les dosages sont suffisamment précis et sensibles. Les variations d'enthalpie de ces réactions sont de l'ordre de 10²-10³ kJ · mol^–1. Les dosages proposés ont l'avantage d'être simples, rapides et susceptibles d'être automatisés

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Enthalpimetric assay of the water content of some oils and fats

A rapid and accurate direct injection enthalpimetric (DIE) method has been developed for the determination of the water content in some oils and fats of commercial interest. The method combines the DIE and the Karl Fischer Reagent procedures and is calibrated against real samples whose water content have been determined by a standard distillation method using toluene as the immiscible solvent. The reproducibility and precision are equivalent to those of the standard method for the water content of materials such as soya bean oil. The procedure is able to determine water contents in compounds such as lard, which cannot be determined by the Dean & Stark method. Once calibrated, the proposed method can be operated routinely by semi-skilled personnel. The main advantages of the method are those of time and the cost of analysis.

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Zusammenfassung Zur Bestimmung des Wassergehaltes einiger kommerziell interessanter öle und Fette wurde eine schnelle und genaue enthalpimetrische Methode mit Direkteinspritzung (DIE) entwickelt. Dieses Verfahren vereint DIE und die Methode nach Karl Fischer und wurde anhand von reellen Proben kalibriert, deren Wassergehalt durch die Standard-Destillationsmethode mit Toluol als nicht mischbares Lösungsmittel bestimmt wurde. Reproduzierbarkeit und Genauigkeit stimmen mit denen der Standardmethoden zur Wasserbestimmung von Stoffen wie z.B. Sojabohnenöl überein. Mit diesem Verfahren kann auch der Wassergehalt von Verbindungen wie Schweinefett bestimmt werden, der mit dem Verfahren nach Dean und Stark nicht ermittelt werden kann. Nach Kalibrieren der Methode kann sie routinehaft auch von angelerntem Personal durchgeführt werden. Die Hauptvorteile bestehen in dem geringen Zeitbedarf und in den Kosten der Analyse.

     

Trace fluoride determination with specific ion electrode

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.     

Laminar Flow-Through Cell for Enthalpimetric Determination of Biological Substrates

Abstract

This paper describes a very versatile laminar flowthrough cell designed to perform enthalpimetric determinations of biochemical substrates in the field of clinical and biochemical analysis. The performance of the apparatus is demonstrated for the glacose/glucose-oxidase system instrument. Sensitivity allows determination of glucose concentrations in the range of 10^?3 Moles/litre. Other enzyme-substrate exothermic reactions can be used without any modification of the instrument.     

The determination of fluoride in environmentally relevant matrices

This report covers analytical methods for the determination of total fluoride in gaseous emissions, rain water and aqueous effluents, vegetation, human urine, factory air and environmental air. All the methods are based on final measurement of fluoride by means of the fluoride ion-selective electrode. Interferences which cannot be eliminated by the masking power of the TISAB buffer solution are avoided by separation of fluoride by steam distillation. Decomposition methods are used for vegetation and for samples which may contain insolubles such as stack gases or aqueous effluents. Sampling of fluoride from air is done by alkaline absorption for the high concentration range (stack gases) and by filter methods for low fluoride concentrations, e.g., in factory and environmental air. Detection limits as low as 0.3 μg m^?3 fluoride can thus be achieved. The methods were established after the individual analytical procedures, common in the various member countries of CTEF, had been compared. Thus, the most practicable method was selected or an optimized version was designed for full testing. The accuracy of the different methods was verified by comparative tests.     

Separation and determination of fluoride in plant samples

A simple and rapid separation method is described for the determination of fluoride in plant samples. Fluoride is separated by distillation in the presence of H(2)SO(4) and H(2)O(2) in a dry air steam. The variables that influence the distillation quantitation were optimized. The fluorides separated were subsequently determined by a spectrophotometric method of the La(III)-F(-)-alizarin complexone system. The precision of the procedure was significant, and the RSD was 3.7%. The accuracy of the method was statistically satisfactory, and the recovery was from 95.9 to 104.4%.     

An automated system for the determination of fluoride

A procedure is reported for the automated determination of fluoride by the method of standard addition. Additions of standard are made via a peristaltic pump and the amounts of standard added are computed from the change in weight of the standard in its container on a digital electronic balance.     

Indirect determination of fluoride by EDTA back-titration of lanthanum

Semimicro to macro amounts of fluoride ion (0.4-100 mg) are determined rapidly and accurately by precipitation with an excess of lanthanum at pH 2.5-2.8 by digestion on a water-bath, cooling to room temperature, addition of excess of EDTA and back-titration of the excess with zinc solution to the Xylenol Orange end-point at ph 5.8-5..9. Large amounts of chloride, acetate and perchlorate, and small amounts of sulphate and silicate do not interfere, but phosphate does. This method is much superior to the usual thorium nitrate titration method and can be applied after preliminary separation of fluorine by steam distillation or pyrolysis.     

The determination of fluoride by titration with calcium chloride

A new method for the determination of fluoride ions is described. Precipitation is effected with an excess of standard calcium chloride and, after standing overnight, the unconsumed calcium ions are back-titrated with ethylenediamine tetra-acetic acid (EDTA) using Eriochrome Black T as indicator. Halides, sulphate, phosphate and arsenate do not interfere under the recommended conditions. The method is applicable over the range 5-65 mg of fluoride ion.     

Rapid titrimetric determination of thorium with fluoride using SPADNS

Summary A rapid titrimetric method for the estimation of thorium in the range from 5 to 88 mg. in a 50 ml. of final volume has been developed which involves the adjustment of P_h at 3.0, addition of 2 ml. of 0.02% SPADNS indicator, dilution to volume and titration with standard NaF until the colour obtained matches a blank containing the buffered solution of the indicator alone. The method has been standardised against known amounts of thorium and a calibration curve relating the titre of the fluoride solution to thorium content has been prepared. Interferences of various cations and anions have also been studied. From the results, the quantitative nature of zirconium interference has been confirmed. The method for the determination of thorium is very rapid and the colour change being sharp from blue-violet to scarlet-red, the detection of endpoint is not at all difficult.The author wishes to thank Dr. A. K. Ghosal, Principal, Darjeeling Government College, for providing Laboratory facilities and Prof. P. Ray and Dr. A. K. Mukherjee of the Indian Association for the Cultivation of Science, Calcutta for their encouragement in the research work.     

阻抑催化光度法测定茶叶中的微量氟化物

在氨基乙酸 HCl缓冲溶液中 ,Fe3+对H2 O2 氧化 2 ,4 二氨基苯酚 (DAP)褪色具有催化作用 ,游离F- 离子与Fe3+形成的稳定络离子 [FeF6]3- 可抑制褪色 ,抑制程度与F- 量线性相关。基于此建立了测定微量F- 的阻抑催化光度分析的新方法。结果表明 ,有色溶液的最大吸收波长为 5 0 0nm ,测定的线性范围为 0～ 9.0mg/L ;摩尔吸光系数为 2 .1× 1 0 5L/mol/cm ;RSD(n =6)为 5 0 %。已应用于茶叶中微量F- 的测定     

Microdiffusion and spectrophotometric determination of fluoride in biological samples

Routine separation of fluoride from large numbers of biological samples (soft and hard tissues) is achieved by microdiffusion from perchloric acid and absorption by sodium hydroxide on filter paper in disposable polypropylene vials. Spectrophotometry with a modified lanthanum/alizarin complexone reagent allows rapid determination of fluoride. Up to 80 samples can be processed per day. Recoveries are in the range 88–102%. Results obtained by spectrophotometry and with the fluoride-sensitive electrode agree within 3–10% for various samples of krill and shrimp products.     

Rapid method for the determination of fluoride in liquids

A rapid procedure has been developed for the determination of total fluoride in liquids. The samples are burned in a modified BECKMAN oxy-hydrogen burner The fluoride is scrubbed out of the products of combustion and determined in any conventional manner