At predetermined time intervals, 5 mL aliquots of the release medium were withdrawn from the release medium, and the same volume of fresh buffer solution was added to continue the release test.
Then, 5 ml samples of dissolution medium were withdrawn at 5, 10, 15, 20, 30, 45, and 60 min and passed through a 0.22 μm microporous membrane filter for HPLC analysis.
At different period of time, 25 µL samples of the reaction medium were withdrawn and mixed with 100 µL of a Pi ALS mixture (100 µL of Pi color lock +1 µL of accelerator, both provided in the Pi color Lock TM ALS kit), previously distributed in a well of a 96-wells microplate.
At appropriate intervals, samples from the dissolution medium were withdrawn and filtered, and concentrations of atorvastatin were determined spectrophotometrically.
Samples of the medium were withdrawn at fixed time intervals and replaced with an equal volume of fresh normal saline for 6 h.
Five millilitre aliquots of the dissolution medium were withdrawn at 5, 10, 15, 30, 45, 60, 90, 105, and 120 minutes.
The release medium was withdrawn for each juncture and replaced with equivalent volume of fresh buffer.
At chosen time points, 1 mL release medium was withdrawn and replaced with an equal volume of fresh medium.
At scheduled time intervals, the release medium was withdrawn and replaced with the equal volume of fresh, filtered medium.
At definite time points, 2 ml of the medium was withdrawn and equivalent volumes of PBS were replaced.
From time to time, 1 ml of the release medium was withdrawn and replaced with equal amount of fresh buffer.
