Media misinterpretations

We shall conclude by saying that the activation phenomenon discussed here is not limited to the activation of an insoluble compound by a more soluble one, but also to the mixture of two or more ionic compounds. As a matter of fact, such property modifications were cited in the literature with organosodium22) and organo-lithium23) compounds for example. What is important, in our opinion, is that in a reaction medium formed by, for example, two basic or nucleophilic entities (A-, M+) and (B-, M+) the observed reactions must be the result of mixed bases or nucleophiles. It is easy to understand what misinterpretation of reaction mechanisms can happen if this possibility is neglected. 

Irrespective of the chosen apparatus, the equipment must be set up and handled in a way that both minimises the variability of the dissolution and avoids artefacts. The most common source to such variability or artefacts is hydrodynamic factors, but unwanted chemical reactions or temperature shifts could also occur. Alterations of hydrodynamics, as well as changes of temperature, can both affect the dissolution of a drug substance and the release of a substance from the dosage form. Chemical reactions in the test medium may cause degradation of the drug substance or some formulation excipient which may affect the dissolution, or may lead to misinterpretation of the results. Examples of different sources to variability for the USP apparatuses are summarised below ... 

Photograph 8-2 Exudation of polishing vehicle (propylene glycol) or cleaning medium (isopropyl alcohol) from an alite cleavage on polished section surface. The exudation could be misinterpreted as chemical attack of the alite crystal. (S A6718)... 

Hydrogen, When using liquid hydrogen as the track medium the chamber was operated at 25,3 to 28. 9 K, The lowest temperature at which tracks were found was 26. l K and above that temperature there were tracks at each test point. Below 26, l K the pictures showed bubbles, indicating sensitivity to radiation but no well defined track formation. It is possible that particles of a different energy would produce tracks in this region. The upper temperature of 28,9 K indicates only the point at which tests were stopped because of a misinterpretation... 

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