Hygrometers and thermohygrometers: environmental monitoring ensures the potency and stability of compounding agents.

Although the terms humidity and relative humidity are often used interchangeably, they are not synonymous. Humidity is the amount of water in the air, and relative humidity is the ratio of the amount of water vapor in the air at a specific temperature to the maximum possible amount of water vapor in the air at that temperature. Thus humidity and temperature are inextricably bound in their effects on the environment. In a compounding pharmacy, humidity can affect the stability and quality of the compounds prepared, as well as equipment, chemicals, and polymers. Devices that measure relative humidity (hygrometers) or humidity and temperature (thermohygrometers) are essential instruments in a compounding pharmacy. They must be chosen carefully, however, to ensure that the measurements they yield are accurate, that they are reliable over time. Most desirable are devices that alert the pharmacist immediately at any time if levels of humidity or temperature at a designated site differ from a specific norm. In this report, we discuss the effects of humidity on the process of compounding and on the agents used in customized preparations. A Table that lists essential features of a variety of hygrometers and thermohygrometers appropriate for use in a compounding pharmacy is presented for easy reference.

Electron transfer and bond-forming reactions following collisions of Cl2+ and HCl2+ with CO.

Collisions between Cl(2+) and CO have been investigated using time-of-flight mass spectrometry over a collision energy range between 2.2 eV and 7.1 eV in the centre-of-mass frame. The formation of Cl(+), CO(+) and C(+) in electron transfer reactions has been detected and an unusual bond-forming reaction which generates CCl(2+) has also been observed. The reactive cross-sections, in arbitrary units, for the electron transfer reactions have been evaluated. To extract these cross sections we employ a new method of analysing mass spectral intensities for crossed-beam experiments, an algorithm which allows inter-comparison of the fluxes of all the ionic products from the electron transfer reactions. The observed electron transfer reactivity has been rationalized by calculations based on Landau-Zener theory. To account for the observation of CCl(2+), we have calculated the relevant energetics showing that the lowest lying doublet state of this dication is bound and is energetically accessible at our collision energies. These energetic arguments indicate that electron transfer in the exit channel between the separating CCl(2+) and O atom probably forms C(+) ions via the dissociation of CCl(+). Additionally, collisions between HCl(2+) and CO have been studied at collision energies from 2.2 to 7.0 eV in the centre-of-mass frame. In this collision system, proton transfer to form HCO(+) is observed to compete efficiently with dissociative and non-dissociative electron transfer.