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Thermogravimetry and vapor pressure moisture

Applications to determination of residual moisture in BCG vaccine

Journal of Thermal Analysis and Calorimetry
Authors: J May, A Del Grosso, N Etz, R Wheeler, and L Rey

Abstract  

Thermogravimetry (TG), thermogravimetry/mass spectrometry (TG/MS), and loss-on-drying methodology are used to provide residual moisture results for freeze-dried biological products regulated by the US Food and Drug Administration. Residual moisture specifications must be met in order to ensure freeze-dried biological product potency and stability throughout the licensed product's shelf life. TG, TG/MS, loss-on-drying and vapor pressure moisture measurements are compared for a BCG Vaccine. Comparisons are made between residual moisture data for the freeze-dried cake and vapor pressure moisture determinations in the space above the freeze-dried cake in the final container. Vapor pressure moisture precision data is presented for α-interferon and BCG vaccine. Impact of residual moisture and vapor pressure moisture upon product stability is presented.

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well as measurement of the vapor pressure of substances [ 16 – 24 ]. Evaporation can be stated as the transition from the liquid phase to the vapor phase, without a change in chemical composition. Several factors such as vapor pressure of the

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dependence of the saturated vapor pressure was measured by the flow method and the standard thermodynamic parameters Δ H T and Δ S T o were determined for the vaporization process of the compounds. The molecule packing in the crystals was considered using

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Abstract  

For a large number of DSC calibration substances the vapour pressure at room temperature or at transition temperature (whichever is the highest) is given. It is important to know the vapour pressure of substances, because a DSC measurement on a substance with a high vapour pressure requires encapsulation of the substance in a hermetically sealed crucible to prevent evaporation. Because the calibration procedure must be performed using the same type of sample pan as will be used during the actual measurements, the presented information allows one to decide which calibration substances and/or what type of sample pan should be used for calibration.

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Abstract  

A new pressure DSC module (Mettler DSC27HP) and its abilities for vapor pressure determination in the range of subambient pressure to 7 MPa are presented. To compare the new to an established method, vapor pressures of caffeine, naphthalene and o-phenacetin have been determined both by pressure DSC and the Knudsen effusion cell method. These results, including the derived heats of evaporation and heats of sublimation, are compared to literature values.

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Abstract  

The Modified Entrainment Method developed by Faktor et al. [1] is an attractive yet not very popular method to determine vapour pressures in the range of 0.002 to 0.1 bar at 10–1000°C. The method consists of evaporating a solid or liquid from a small bulb through a capillary into a flowing inert gas, e.g. argon. The vapour pressure of the sample is related to the rate of evaporation and some easily controlled experimental parameters. In the present paper a new convenient experimental set-up is described and its use to study the decomposition of metal complexes is illustrated.

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Abstract  

The temperature dependency of the saturated vapor pressure of Ir(acac)3 has been measured by the method of calibrated volume (MCV), the Knudsen method, the flow transpiration method, and the membrane method. The thermodynamic parameters of phase transition of a crystal to gas were calculated using each of these methods, and the following values of ΔH T 0 (kJ mol−1) and ΔS T 0 (J mol−1K−1), respectively, were obtained: MCV: 101.59, 156.70; Knudsen: 130.54, 224.40; Flow transpiration: 129.34, 212.23; Membrane: 95.45, 149.44 Coprocessing of obtaining data (MCV, flow transportation method and Knudsen method) at temperature ranges 110−200C as also conducted:ΔH T 0 =127.92.1 (kJ mol−1 ); ΔS T 0 =215.25.0 (J mol−1 K−1 ).

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Abstract  

In order to determine the applicability of vapor pressure studies on polymorphic modifications, pairs of enantiotropically related modifications of caffeine, theophylline and carbamazepine were investigated. The studies were performed over a wide temperature range (71 to 191°C) and accordingly over a wide vapor pressure range (0.02 to 400 Pa) using an automatic instrument constructed on the basis of the gas saturation principle. This instrument enables an analytical determination of the main component and the impurities present by the chromatographic separation of the substances transported in the gas flow. Therefore, the real partial pressure of the main component can be measured. Due to the high precision of the applied method it was possible to determine partial pressure curves and the thermodynamic transition temperature — the point at which the vapor pressure of two crystal polymorphs is equal. The thermodynamic transition temperatures of caffeine and theophylline were determined to be 136 and 232°C, respectively. These values are in agreement with experimental or calculated values derived from DSC investigations but are more reliable. Vapor pressure measurements of carbamazepine are only meaningful in the low temperature range due to its decomposition at high temperatures. The thermodynamics, advantages and limits of vapor pressure determinations of polymorphic modifications are discussed.

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Abstract  

There is considerable interest in performing volatilisation and evaporation measurements by thermogravimetry. A quick and simple method for determining vapour pressure using a conventional thermobalance and standard sample holders has been developed. These yield meaningful thermodynamic parameters such as the enthalpies of sublimation and vaporisation. Under favourable conditions the melting temperature and enthalpy of fusion of such compounds can be obtained. This technique has been used for the study of dyes, UV absorbers and plasticisers. The use of modulated- temperature programs for such work is also described.

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Abstract  

A thermoanalytical study of the diethyldithiocarbamates of the platinum metals Pt(II), Pd(II), Rh(III), Ir(III) and Ru(III) was carried out by means of DTA techniques in an inert atmosphere and in vacuum. Decomposition temperatures were determined and the mass loss curves were obtained for these compounds in helium and in vacuum. The X-ray diffraction patterns of the solid products of M(dtk)n thermolysis were studied. The temperature dependences of the saturated vapour pressures of the listed chelates were measured by flow and Knudsen methods, and the vaporization parameters were determined.

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