The " dissolution" method: a low volume, apparatus for assessing the dissolution/precipitation behaviour of an active pharmaceutical ingredient under biorelevant conditions.

This paper describes a low volume, in vitro apparatus for investigating the dissolution and precipitation behaviour of active pharmaceutical ingredients (APIs) under a wide range of experimental conditions and dissolution media. The apparatus has automated and dynamic pH control, allowing the simulated passage of drugs through the gastrointestinal tract (GIT). Experiments can be performed in the presence of biorelevant media and excipients, providing information related to the predicted behaviour of APIs under physiological conditions.

A multidimensional study of the reaction CH2I+O2: products and atmospheric implications.

The CH(2)I+O(2) reaction has been studied using laser flash photolysis followed by absorption spectroscopy, laser-induced fluorescence spectroscopy and mass spectrometry. The rates of formation of IO and CH(2)O were found to be dependent upon the concentration of CH(2)I(2) under pseudo-first-order conditions ([O(2)]≫[CH(2)I(2)]), demonstrating that IO and CH(2)O are not formed directly from the title reaction, in contrast to recent investigations by Enami et al. It is proposed that the reaction proceeds via the formation of the peroxy radical species CH(2)IO(2), which undergoes self-reaction to form CH(2)IO, and which decomposes to CH(2)O+I, and that in laboratory systems IO is formed via the reaction I+CH(2)IO(2).

New ideas about the solubility of drugs.

Methods are described for detecting precipitation of ionisable drugs under conditions of changing pH, estimating kinetic solubility from the onset of precipitation, and measuring solubility by chasing equilibrium. Definitions are presented for kinetic, equilibrium, and intrinsic solubility of ionisable drugs, supersaturation and subsaturation, and for chasers and non-chasers, which are two classes of ionisable drug with significantly different solubility properties. The use of Bjerrum Curves and Neutral-Species Concentration Profiles to depict solubility properties are described and illustrated with case studies showing super-dissolving behaviour, conversion between crystalline forms and enhancement of solubility through supersaturation, and the use of additives and simulated gastrointestinal fluids.

Kinetics study of the reaction of iodine monoxide radicals with dimethyl sulfide.

The temperature and pressure dependence of the rate coefficient for the reaction of iodine monoxide radicals with dimethyl sulfide (DMS), IO + DMS --> I + DMSO (1), was studied using laser induced fluorescence (LIF) to monitor the temporal profile of IO following 351 nm photolysis of RI/DMS/NO2/He (RI = CH3I/CF3I) mixtures. The study was performed over the range T = 296-468 K yielding a positive activation energy and k1 = (9.6 +/- 8.