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The following article has been authored by Chris Lewis. At times during dissolution testing, particularly with USP Apparatus 2 (paddle), a ‘cone’ can form in the bottom of a dissolution vessel.  This ‘cone’ is the result of the accumulation of undissolved material, such as excipients or drug particles, directly beneath the stirring paddle. This occurs because the center of the vessel's hemispherical bottom is a hydrodynamic "dead zone" where hydrodynamic shear forces are too low to lift the particles which allow gravity to settle them in a cone shape. Key Causes of Coning •                     Low Hydrodynamic Activity (Dead Zone): The...

Sample filtration is a critical part of dissolution testing, yet there is no universal solution that works for every application. The most effective filtration approach depends on the specific analytical method, sample properties, and filter characteristics involved. Each method should be evaluated individually to ensure optimal performance and reliable results. For established methods that already specify a particular filter type or micron rating, there may be little flexibility in filter selection. However, when developing new methods, a successful filtration strategy should be based on three key considerations: 1. Analytical Method Requirements The analytical technique being used—typically UV spectroscopy or HPLC—plays...

Polytetrafluoroethylene (PTFE) coatings are frequently used on Dissolution bath accessories. Many individual monographs specify this coating on Sinkers, Baskets, Paddles and Vessel interiors. The coating on the accessories can, over time, develop chips or scratches that can expose the substrate to corrosion and affect the results of the test. Technicians handling these coated parts should be familiar with the following guidelines to help extend their service life. Parts with corrosion should be removed from service.  Handling The PTFE coatings are applied at the factory in order to maximize adhesion and durability. The coating, however, is susceptible to chipping and scratching...

The following article has been authored by John Heaney. Push-on style baskets have been used for dissolution testing for quite a few years at this point.  While they’re generally accepted as equivalent to the clip style baskets pictured in USP <711>, it’s important to be aware of the differences between the two designs.  Both have some advantages and disadvantages depending on the method. The clip style is officially recognized in <711>, so there is never any debate as to whether the clip style baskets are acceptable for testing.  Furthermore, all the wetted materials are 316 Stainless Steel, which is chemically...

  The following article has been authored by John Heaney. Intrinsic dissolution is a specific niche of dissolution testing often reserved for early R&D.  The purpose is to provide scientists with an idea of the solubility of the API they’re studying.  This data can be invaluable as it will help determine the excipients required to develop an oral dosage form. There are 2 types of methods for this.  The first is a Rotating Disk (often called the Wood’s Apparatus) and the second is Stationary Disk.  In both cases a pellet of the pure drug is pressed into a drug compact...