Many companies still rely on MDT to test blister packs are sealed properly and have no leaks, even though the procedure is messy, prone to error, destroys the packs tested and cannot be validated as part of an audit trail. The test involves placing the packs in the dye, raising the pressure and checking visually if any dye penetrates into the blisters.
There has been a move towards replacing the methylene blue test - which is cumbersome, messy and slow - with new automated systems based on vacuum testing or tracer gases. These are non-destructive and much faster, but these benefits come at a price. Mocon's new unit refines the MDT but is significantly less expensive than rival non-destructive blister testing units, according to the manufacturer.
The Lippke Blister-Tester VC 1380 incorporates a bowl-shaped chamber filled with water to which the blue dye is added. The filled blister is placed at the bottom of the bowl and secured in place by a screen to insure submersion. A lid is placed over the bowl.
The approved user then enters a PIN into the blister-tester console which features an LCD display. (Only authorized users whose identities are stored in the unit's database can administer the test.) The parameters for vacuum, test time and penetration time are adjustable and can also be stored in a database. This ensures that identical products will always be tested with the same parameters.
Pressing the start button activates the test which begins when vacuum is created inside the bowl-like chamber. The blister packs remain in the methylene blue die under atmospheric pressure, for a predetermined amount of time. If there is a leak, pinhole, etc., in the individual blisters or in the backing seal, the dye-filled water will breach the structure and penetrate the specific cell. After the test is concluded, inspection of the blister pack will immediately yield visual results.
By automating the test sequence, users can insure that tests are conducted under the same parameters. Further, automation enables staff to focus on other work-related tasks while this test is cycling through, according to Mocon. Documentation also is simplified via automatic printout of the test report.
The VC 1380 can also be used for the testing of ampoules and vials, according to the company.