Enthalpimetric Method Research Articles

A Novel Thermal Infrared Enthalpimetric Method for Fast, High-Throughput Determination of the Content Uniformity of Captopril Tablets

A Novel Thermal Infrared Enthalpimetric Method for Fast, High-Throughput Determination of the Content Uniformity of Captopril Tablets

Heat capacity and phase equilibria in rare earth alloy systems. R-rich R-Al alloys (R=La, Pr and Nd)

Molar heat capacities of the R-Al (R=La, Pr and Nd) R-rich alloys were determined at different temperatures by differential scanning calorimetry both by using the stepwise and the enthalpimetric methods. The results obtained for the molar heat capacity of αPr 3Al, βPr 3Al and Nd 3Al phases have been reported together with the values obtained for liquid La–Al alloys ( x Al=0.25). The characteristic temperatures obtained for the different invariant reaction involved in the R-rich region have been compared with the literature data. The α↔βPr 3Al transformation has been confirmed at 330°C and a value of Δ trs H≅+0.09 kJ/mol of atoms obtained for the transformation enthalpy.

Diodes as sensors in solution thermochemistry

The advantages of using diodes as thermal sensors in solution thermochemistry are discussed and a simple, low-cost circuit for the use of diodes as temperature sensors is reported. In preliminary studies, the titration of TRIS and hydrochloric acid is used to compare the precision of thermistors and diodes in thermometric titrimetry. Several systems are assayed at various temperatures by enthalpimetric methods to illustrate the advantages of diodes as sensors for monitoring thermal methods capable of being used in quality control system.

Nomenclature of thermometric and enthalpimetric methods in chemical analysis (IUPAC Recommendations 1994)

Article Nomenclature of thermometric and enthalpimetric methods in chemical analysis (IUPAC Recommendations 1994) was published on January 1, 1994 in the journal Pure and Applied Chemistry (volume 66, issue 12).

Rapid enthalpimetric method for the determination of thiol compounds in petroleum oils

A rapid method is proposed for the determination of thiol sulphur in petroleum oil fractions. The thiol is reacted with phenylmercury(II) acetate in a kerosene medium. By adjusting the sensitivity of the system the heat changes are usable over a wide range of concentrations of the analyte (from 0–10 to 50–100 mM thiol) in the oil.

A rapid enthalpimetric method for the assay of the reducing sugar content of some soft drinks

An enthalpimetric method for the rapid, low cost assay of reducing sugars in soft drinks is reported.

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.

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.

A rapid method for determining the casein content of milk

A method is presented for the rapid determination of the casein content of milk by Direct Injection Enthalpimetry (DIE).A significant heat pulse of precipitation of casein is produced by adjusting the pH of the solution to the pH of the isoelectric point of casein. The method is calibrated against a real sample whose casein content has been determined by a standard method incorporating the time consuming Kjeldahl method, but once calibrated the proposed method can be operated routinely by non-skilled personnel. The method is sensitive and gives results as acceptable as those obtained by standard methods. The method can be applied to most liquid samples without the need for prior preparation. the main advantages of the method are those of time and costs of analysis and the potential of the enthalpimetric method for automation.

Determination of ethanol using flow injection enthalpimetry.

A flow injection enthalpimetric method for the determination of ethanol in fuel-grade ethanol, based on the heat of dilution of ethanol, is described. The accuracy and precision were 0.05% of ethanol; interferences by several substances are discussed. A similar procedure was also applied to the determination of ethanol in wines and spirits after distillation, yielding a precision of 0.03–0.1% of ethanol. The sampling rate in both procedures is 110 h–1.

Strömungsenthalpimetrie

AbstractFlow‐through enthalpimetric methods are efficient and cheap measuring techniques for laboratory and industry, but they are used only rarely. Possibilities and limits of using are discussed and proposals for construction are given.

Determination of residual unsaturation in polyene preparations by direct injection enthalpimetry

Direct injection enthalpimetric methods for the determination of residual unsaturation in both water and hydrocarbon soluble polymers are described. Both methods are based on the heat of bromination of double bonds. The method for water-soluble polymers is a new method, while the method described for hydrocarbon-soluble polymers is a modification of literature methods which makes these previous methods simpler and quicker to use.

Calorimetric monitoring of industrial chemical processes

Enthalpimetric methods used in chemical production and in process development are reviewed. On-line methods are applied to concentration analysis, to safety monitoring and to the control of reaction progress. The most promising applications of thermal methods are found in process development: enthalpimetric process investigation on the bench scale. Design principles for “process calorimeters” are outlined and applications to a pressure reaction, to a highly unstable radical reaction and to fermentations are shown.

Catalytic—enthalpimetric determination of diethyldithiocarbamate (DDTC) and nickel(II) using the iodine—azide reaction

An enthalpimetric method for the determination of diethyldithiocarbamate (DDTC) based on the catalysis of the iodine—azide reaction is proposed. The behaviour of those metal ions which inhibit the catalytic activity of DDTC by complex formation is also studied, and a simple and rapid procedure for the determination of trace amounts of nickel(II) is described. The relative standard deviations are within 2 and 3% for concentration levels of 2×10 −5 M DDTC and 2×10 −6 M nickel(II), respectively.

Flow enthalpimetric determination of glucose, based on oxidation by 1,4-benzoquinone and use of an immobilized glucose oxidase column

A flow enthalpimetric method for the determination of glucose is presented. The method is based on the reaction of glucose with 1,4-benzoquinone in the presence of immobilized glucose oxidase. d-Glucose concentrations ranging from 0.02 to 75m M can be determined. The method is applicable to the determination of glucose in soft drinks, wines, beers, jams and serum.

Enthalpimetry with catalytic reactions—II: Determination of thioureas by the iodine—azide reaction after thin-layer chromatographic separation

A enthalpimetric method for the determination of thiourea and its N-alkyl derivatives (1,3-dimethyl, 1,3-diethyl and 1,3-di-n-butyl), based on thei

The determination of horse-radish peroxidase activity by enthalpimetric and potentiostatic measurements

An enthalpimetric method is described for the determination of peroxidase activity based on the heat produced by the peroxidase-catalysed oxidation of iodide by hydrogen peroxide. Two other electron donors, hydroquinone and ascorbic acid, were found to be less suitable as substrates. The method described allows the determination of peroxidase activity in the range 2–79 IU with an r.s.d. of 3%. A potentiostatic method in which the iodide concentration is kept constant by the automatic incremental addition of sodium thiosulphate, gave activity measurements slightly less than the enthalpimetric method.

The enthalpimetric determination of the michaelis constant of the α-chymotrypsin-catalysed hydrolysis of n-acetyl-l-tyrosine ethyl ester based on the integrated michaelis—menten equation

An enthalpimetric method is discussed for the determination of the Michaelis constant ( K m )for the α-chymotrypsin-catalysed hydrolysis of N-acetyl-L-tyrosine ethyl ester (ATEE). The integrated form of the Michaelis—Menten equation is used to achieve a graphical determination of K m in a single experiment (s r = 7.6%). The inhibitory effect of ethanol is briefly described.

The chemistry of uranium. Part XII. Nitrate complexes of uranium(IV) and thorium(IV)

The behaviour of [NO3]– as anionic ligand towards ThIV and UIV in the presence of various amounts of trimethylphosphine and tris (dimethylamino)phosphine oxides has been studied in non-aqueous media by conductometric, spectroscopic, and enthalpimetric methods. The relation between species present in solution and solids isolated and the influence of cation-and neutral-donor ligand size on the action of nitrate as a donor have been investigated.

Direct enthalpimetric microdetermination of allylic and vinylic unsaturation

This paper described an extension of the authors' method for direct enthalpimetric determination of olefins to six compounds containing allylic or vinylic unsaturation. Solutions of allylbenzene, allylcyclohexane, allylcyclopentane, methallylbenzene, vinylcyclohexane and vinylcyclopentane in concentrations of 26.4–184μmol have been analyzed with a standard deviation of 1 to 3 %. Under the conditions described, allylic and vinylic unsaturation in these compounds can be determined in the presence of aromatic unsaturation with no interference. Preliminary results for two compounds for which the enthalpimetric method is unsuccessful or at least suspect, allyl acetate and styrene, are also reported.