News — dissolution sampling

The following article has been authored by John Heaney. While automation is prevalent with dissolution testing, manual testing can and still should be done in certain circumstances.  This can be when automation is too expensive, when the method is being developed and a certain amount of flexibility is needed, or when sample times are too short to be completed by automated systems.  Manual sampling does offer significant flexibility but it also has some factors that need to be considered to ensure consistency. Sampling height is clearly defined in USP <711> as half-way between the top of the apparatus, be it...

The following article has been authored by John Heaney.  Coning of disintegrating dosage forms is fairly common when using Apparatus 2 (Paddles) to perform dissolution testing.  The reason for this is the spinning of the paddle causes a cone shaped zone to form directly beneath it where there is low hydrodynamic activity.  In other words, it’s a bit of a dead zone where the stirring has little effect, and the particles are allowed to settle. Depending on the formulation this coning can be problematic.  It can prevent drug from dissolving in the media due to a reduction in the effective...

The following article has been authored by John Heaney.  Filtering is a required step in processing dissolution samples as it both stops the dissolution of larger particles by separating them from the sample and removes any material that may interfere with the analysis by UV/Vis spectroscopy, HPLC, or UPLC.  There are a plethora of materials, shapes, sizes, and porosities available to choose from to ensure that a filter is appropriate for a specific method.  In many cases it’s possible to find equivalent filters from other suppliers.  However, that equivalence needs to be proven, ideally during the development of the dissolution...