Powder sampling is a common practice in Pharmaceutical industries. The principle is a simple one. Because the Analysis of large quantities of powder would be wasteful and expensive, a small sample of powder is taken to represent the batch.
This sample then moves on to the labs for analysis and can serve for a number of purposes. Most often, it’s used as a process in quality control.
We’ve set out to answer any questions you might have about Powder Sampling in Pharma.
What’s Powder Sampling and What Should You Look Out for?
Powder sampling, as discussed, is the practice of taking a small sample of powder to analyze as a representation of the batch it was taken from. In order for this to effectively inform about the qualities of the powder at a higher quantity, the sampler needs to take care to mind a few things.
First of all, the composition of the original powder has to be retained during the sampling process. The selection method has to ensure that the powder characteristics don’t change once removed from the batch. For reliable samplers, the correct sampler design has to be used.
With any powder sample, the sampler also has to avoid taking powder from the top of a stored powder supply. This is because fine particles sink lower. The coarser particles at the top begin to unmix and segregate. It’s possible to mitigate this bias by taking a sampler from deeper down the heap or mixing the sample beforehand.
Samplers also need to take care to always sample from a moving stream of powder for optimal results. And finally, they should sample the whole stream for equal intervals of time, instead of taking from the same part of the stream constantly.
Powder Sampling Method
Static Sampling
This is the process of taking a sample from a static heap or store. Surface samples tend to not be representative of the bulk, so a sample thief is used to plunge deeper into the material and retrieve a several small samples.
Dynamic Sampling
Dynamic sampling is often superior to static sampling because the powder doesn’t get a chance to separate. There are several ways to proceed with dynamic sampling.
Table sampling uses an inclined table with a series of holes onto which the powder is flowing. These holes filter out finer particles and occur at several intervals before the final powder sample arrives at the end of the table.
Another method is to use a chute splitter, which repeatedly halves a sample until the desired sample size is obtained.
What Different Types of Powder Samplers Are There?
There are not many types of Powder Samplers but sampling can occur manually or automatically. These are just some examples of tools that can be used for powder sampling.
Manual Sampling with a Sample Thief
Manual sampling uses a sample thief. This is a needle-like tool with a hollow interior into which free-flowing powders can be absorbed. The sampler consists of two concentric tubes. One encloses the other. The exterior tube is pointed and includes holes that correspond to holes on the interior tube, where the powder will be stored.
When you want to collect a sample, you can twist the shaft to open it and take in powder from the stream. There are several types of sample thieves.
Some include holes along the tube for the segregation of the powder. Others consist of the full-length chamber and are used for spot sampling. And finally, there are those with a chamber at the appointed end that can be used to gain an average from many samples.
Semi-Automatic Sampling
The sampling process benefits from regular, consistent intervals. That’s why it is an often Automated process. A pneumatic lance can be used for bulk powders. This draws in a sample with a reverse air flow. The powder then collects at the other end of the probe.
Here, a porous plate filters fine powders from prevailing in the sample.
Alternatively, vacuum probe samplers can take large samples from bins or holds with a similar principle to vacuum cleaners.
Conclusion
There are many methods of powder sampling that have been designed to work with the consistency and weight of powder you are working with. Where possible, follow the golden rules of sampling: Sample powder when it is in motion, and take samples from the whole stream for many short increments of time.
Effective Powder Sampling achieves a high degree of reliability. It’s important to develop and implement protocols and practices in the sampling procedures that document and help eliminate errors.
