Direct Enthalpimetry. A New Thermochemical Approach to Quantitative Analysis.

1991

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.

mentioning

confidence: 99%

A rapid method for determining the casein content of milk

1991

“…Since the halogen addition reaction generally releases a significant amount of heat, and the reaction could be forced to occur immediately by the use of a large excess of reagent, the Direct Injection Enthalpimetric (DIE) method [11] potentially provides an ideal technique to satisfy the problem of providing a rapid method of analysis. The reported potential uses of iodine monochloride in solution thermal chemistry [12], indicate that it should be useful for the rapid determination of the amount of unsaturation in oils and fats.…”

mentioning

confidence: 99%

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

1991

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, linoleie 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 enthalpimetrie method for automation.The "iodine value" of oils and fats is one of the most valuable and widely used characteristic for the evaluation and differentiation of these substances representing as it does a measure of the degree of unsaturation. For some time the determination of this value has been of universal importance, and there is, at present, a steadily increasing demand for a simple and rapid method which will be adaptable for routine work, will require no special apparatus and be relatively economical in use. In spite of this, no single, rapid and accurate method which will give consistent results on all types of oil has been previously reported.John Wiley & Sorts, Limited, Chichester AkadOniai gdad6, Budapest

“…The technique of Direct Injection Enthalpimetry (DIE) [25] combined with the Karl-Fischer method provide additional sensitivity to a method for water determination in some organic solvents [26]. Binary mixtures of water and miscible organic liquids have been analysed by injection into sulphuric acid [27].…”

mentioning

confidence: 99%

Enthalpimetric assay of the water content of some oils and fats

1991

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.Chemically, the principal roles of water in foods include: (a) solvent, (b) reaction medium, (c) reactant, (d) antioxidant, (e)pro-oxidant, (f) a component of intramolecular structure and intermolecular structure [1]. Consequently, an ability to determine the water content is vital in ascertaining stability and thermal behaviour in connection with the processing and the packaging of foodstuffs.Many industrial food processes require reliable quantitative methods for the determination of moisture or water since water enters directly or indirectly into many chemical reactions. In response to this widespread need for reliable analysis, a wide array of methods [1][2][3] is presently available to cover the range of water content from parts per billion to high percentages by weight and volume, but all, even the widely used Karl-Fischer Reagent technique, suffer some limitations. Thus, a study of a new technique, such as Direct Injection Enthalpimetry is potentially of great interest to the analytical chemist.