The complexity and uniqueness of disposable medical devices (DMDs) requires thorough analytical investigation to ensure their quality and stability upon storage. Infusion sets were studied in this context. Chemical compositions of various parts of these medical devices were analyzed using spectroscopic and chromatographic techniques. Physical properties of the components were tested according to appropriate American Society for Testing and Materials (ASTM) procedures (swelling and leaching test, tensile strength and microhardness). Since degradation of polymers is often accompanied by a color change, the yellowing observed in the chosen items was considered as an indication of degradation. Swelling and microhardness tests indicative of a correlation between the plastics' shelf‐life and their degradation extent. Analyses of extracts of the plastics in different solvents confirmed the presense of a common plasticizer diethylhexylphthalate (DEHP) and two widely used antioxidants butylated hydroxytoluene (BHT) and methylenebis(methyl‐t‐butylphenol) in different parts of the devices. The mentioned compounds were identified by high performance liquid chromatography (HPLC) and gas chromatography and mass spectrometry (GC/MS) techniques. The concentration of these compounds in the extracts may be correlated with aging of the examined parts of the infusion sets. The quality of DMDs may deteriorate due to the field storage conditions. Development of qualititative and quantitative methods for evaluating this deterioration is essential for better quality control of these items. Copyright © 2007 John Wiley & Sons, Ltd.
NATURE 801 occurs ; they are as pronounced with pepsin, which does not dissociate, as with hoorooglobin which does. The specificity of amides for both effects and the repeated occurrence of the amide bond in proteins suggest that the two phenomena may nevertheless have related causes. They do not appear to be related to changes in dielectric constant. Urea and formam ide solutions have dielectric constants greater, and acetamide solutions much smaller, than that of water. Glycine solutions, with dielectric constants still higher than those in urea, are without effect on dissociation, and have relatively small influences on solubility. These measurements were made possible by the facilities provided by Prof. The Svedberg at Uppsala, and by Sir Joseph Barcroft at Cambridge.
A method based on a refined measurement equation is proposed for enhancing the accuracy of measurements of the specific heat of solids. The equation uses calorimetric and gravimetric output signals along with analytical representation of the output and baseline signals.Thermogravimetry has come into widespread use in thermal analysis of materials [1]. It is especially valuable when employed together with other forms of measurement, in particular with calorimetric measurements [2, 3]. This produces a fairly detailed picture of the thermal effects, gives a picture of the calorimetric experiment in detail, and substantially increases the reliability of the calorimetric measurements for materials that change in mass during heating.Effects associated with change in mass can be physical (sublimation, evaporation, sorption, desorption) as well as chemical (destruction, release of bound water, oxidation, reduction, etc.). Even when those effects are very small, they ma3~ affect the results of measurements of specific calorimetric characteristics (per unit mass of matter) at the level of errors of measurements on standard equipment and sometimes at a higher level.It is qualitatively clear that effects due to the complex variation of the mass of the specimen must be taken into account when formulating and solving problems of metrological assurance of calorimetric measurements, in particular during the development of standard specimens for heat capacity [4] and heat of phase transitions, as well as when assessing the reliability of measurements of the calorimetric characteristics on standard measuring instruments.The accuracy of measurements of the heat capacity Cp of solids, accompanied by substantial changes in the mass of the specimens because of the application of the combined DSC + TG method (differential scanning calorimetry + thermogravimetry) cannot be increased because no specific procedures for making the measurements are available. Such procedures should contain: m a refined equation of measurement, in which both the calorimetric and thermogravimetric output signals appear; and --a method for analytic description of the output signals, which is construed also to mean the choice of method for analytical description of the baselines of the respective signals. Both the refined measurement equation and the related formulas for evaluating the total error (or its individual components) should contain only the functional relations (baselines, output signals, etc.) directly measured experimentally or tabulated values of some physical quantifies (heat of sublimation, thermal effects of oxidation reactions, etc.).Below we propose such a procedure for heat capacity measurements by means of a DSM-2M differential scanning calorimeter and a thermogravimetric apparatus developed at VNIIM (D. I. Mendeleyev All-Russian Research Institute for Metrology).Qualitative analysis of the factors that distort data concerning the heat capacity of specimens of solids, with a mass that varies during measurements, showed that the main factor...
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