Reasons behind black spots on tablets
Black spots on tablets during compression are quality issues and must be rectified by identifying the root cause in this article we will discuss some possible reasons of black spots and their rectification.
Possible reasons of black spots are.
- Raw material to be compressed already contain black spots.
- Lubrication oil on tablet press dries and circulates freely in air and finally settles on blend leading to black particles. Rectification in this case is proper cleaning and lubrication.
- If the spots are metallic Grey in color those may be of alluminium scrapping away from feed frame. Rectification in this case is visually ensure proper assembly of feed frame and empty run is recommended to identify any sound of metal touch.
- Scrapper blade may be scrapping away. Rectification of above case is done by proper assembly of scrapper blade.
- Feeder wheel might be rubbing against housing of feed frame . Rectification is done by manual checking of free movement of feeder wheels
- If black spots are appearing on both sides of tablet it could be of lubrication oil that has mixed up with blend in feeder.
- Spots of lubrication oil on tablets because we have not assembled dust caps is also common cause.
- In some cases incorrect filling cam or too deep fill cam is also the cause consider a situation Too deep fill cam and excessive lubrication oil on punches if vacuum pickup is bad the fines generated during compression will get deposited on punches leading to black oil particles which may find the access to blend leading to black spots.
However, we should not always assume the black particles or spots are coming for machine or raw materials sometimes active ingredients of batch reacts with each other or with excipients due to incompatibility or excessive moisture conditions leading to spots on tablets.
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