The Environmental Protection Agency has estimated that 20,000 lung cancer deaths per year may be related to radon exposure. This paper briefly describes the approach used to derive the Agency's central estimate of risk to the population. The weight-of-evidence for classifying radon as a known human carcinogen and the uncertainties associated with estimating risks from radon exposure provide an important context for these estimates and are briefly discussed.
Summary Chloroprocaine hydrochloride (2-CPCHC) is a local anaesthetic agent of the ester type preferentially used for epidural anaesthesia. The compound, official in the USP, was found to exist in two polymorphic crystal forms which have been characterized by thermomicroscopy, differential scanning calorimetry (DSC), pycnometry, FTIR-, FT-Raman-spectroscopy as well as X-ray powder diffractometry. Based on these data the relative thermodynamic stability of the two forms was determined and is represented in a semi-schematic energy/temperature diagram. Mod. I° is the thermodynamically stable form at room temperature. This form is present in commercial products and can be crystallized from ethanol. Mod. II can be obtained by annealing the supercooled melt in a temperature range between 100 and 130°C. Upon heating mod. II exhibits an exothermic phase transition (ΔtrsHII-I: -5.0±0.5 kJ mol-1) at about 134°C to mod. I° (melting point 175°C, ΔfusHI: 46.6±0.6 kJ mol-1). The exothermic transformation of mod. II to mod. I° confirms that mod. I° is thermodynamically stable in the entire temperature range (heat of transition rule) whereas mod. II is monotropically related to mod. I°, i.e. is metastable at all temperatures below its melting point. Mod. II is of low kinetic stability at room temperature and the transformation to mod. I° starts within a few minutes at room temperature. The N-H band in the infrared spectrum of mod. I° (3433 cm-1) lies at significantly higher wavenumbers than that of mod. II (3413 cm-1) indicating differences in the hydrogen bonding arrangement. Furthermore, the measured density of mod. I° is lower than the density of mod. II and thus both, the IR- and the density-rule are violated in this polymorphic system.
The aim of this paper is to determine temperature and structural changes caused by tableting and to deduce from the combination
of temperature measurement and the determination of structural changes whether temperature increase induced by tableting contributes
to tablet quality. Tablets were produced of microcrystalline cellulose (MCC), spray-dried lactose, pregelatinized starch,
and dicalcium phosphate dihydrate (DCPD) with an instrumented single punch tableting machine. The temperature pattern at the
surface of the tablets was measured starting directly after tableting with an infrared thermoviewer and an infrared sensor.
Powder and tablets were analyzed by FT-Raman spectroscopy, the tablets were analyzed directly after tableting and after one
month of storage. The crushing force of the resulting tablets was determined. For all materials a temperature increase (TI)
induced by tableting was determined with both methods used. The order of the temperature increase was the same for both methods
used: TI (MCC)>TI (spray-dried lactose)>TI (pregelatinized starch)>TI (DCPD). The order was also identical for the crushing
force of the tablets. The extent of differences in the spectra followed the same ranking. In conclusion, the temperature increase
contributed to the changes in material structure and thus temperature increase is one factor which determined crushing force
and thus tablet properties.
The physical aging characteristics of maltose glasses aged at two temperatures below the glass transition temperature, Tg, (Tg-10C and Tg-20C) from 5 to 10 000 min were measured by standard differential scanning calorimetry (SDSC) and modulated differential
scanning calorimetry (MDSC). The experimentally measured instrumental Tg, the calculated Tg, and the excess enthalpy values were obtained for aged glasses using both DSC methods. The development of excess enthalpy
as a function of aging time, as measured by both SDSC and MDSC, was fit using the Cowie and Ferguson and Tool-Narayanswamy-Moynihan
models. The change in the Tg values and the development of the excess enthalpy resulting from physical aging measured by the two DSC methods are discussed.
Crystal polymorphs of pramocaine hydrochloride (PRCNC) and pramocaine (PRCN) free base were produced and characterized by
means of thermomicroscopy, differential scanning calorimetry (DSC), FTIR- and FT-Raman-spectroscopy as well as X-ray-powder
diffractometry. The relative thermodynamic stabilities of all forms were determined and are represented in semi-schematic
energy/temperature diagrams. PRCN, which is a viscous liquid at room temperature and insoluble in water, was found to exist
in two different crystal forms with the melting points 23.5C (mod. I) and 12.5C (mod. II). The water-soluble PRCNC crystallizes
in three different crystal modifications. Mod. II is the thermodynamically stable form at room temperature and is present
in commercial products. This form is obtained by crystallization from solvents and transforms on heating at about 95C into
the high temperature form mod. I which melts at 171.0C. Both compounds show conformational polymorphism with forms of low
Authors:A. Schmidt, V. Niederwanger, and U. Griesser
Two polymorphic forms, a dioxane solvate and the amorphous form of the local anaesthetic drug prilocaine hydrochloride (N-(2-methylphenyl)-2-propylamino
monohydrochloride, PRCHC) were characterized by thermal analysis (hot stage microscopy, differential scanning calorimetry,
thermogravimetry), vibrational spectroscopy (FTIR, FT-Raman-spectroscopy), powder X-ray diffractometry and water vapor sorption
analysis. The formation and thermodynamic stability of the different solid phases is described and presented in a flow chart
and an energy temperature diagram, respectively. Mod. I (m.p. 169C) is the thermodynamically stable form at room temperature and present in commercial products. This form crystallizes
from all tested solvents except 1,4-dioxane which gives a solvate with half a mole of 1,4-dioxane per mole PRCHC. Mod. II
occurs only on desolvation of the dioxane solvate and shows a lower melting point (165.5C) than mod. I and a lower heat
of fusion. Thus, according to the heat of fusion rule, mod. II is the thermodynamically less stable form in the entire temperature
range (monotropism) but kinetically stable for at least a year. Freeze-drying of an aqueous solution leads to the amorphous
form. On heating and in moist air amorphous PRCHC exclusively crystallizes to the stable mod. I. PRCHC exemplifies that certain
metastable polymorphic forms are only accessible via a specific solvate, but not via any other crystallization path. Since
no crystallization from 1,4-dioxane was performed in earlier solid-state studies of this compound, PRCHC was to this date
rated as monomorphic.
The NRTL model has been used to correlate the data for the aqueous alkanolamine systems of (MEA+H2O), (DEA+H2O) and (MDEA+H2O). The model was successfully applied to correlate simultaneously the excess enthalpy, vapour-liquid equilibria, and low
temperature activity coefficients. A large database of data was collected for the investigation and it covers a wide range
of composition, temperature and pressures. It was found that the form of the binary interaction parameters used by Posey (1996)
with a variable non-randomness parameter gave the best results.