Drug release over 100% is common and is related to cumulative normal experimental error/variations in both the manufacturing and testing of the doses. It's seen for all solid drug doses. Even if you put a reference dose that is expected to result in 100% release, if you run several preparations you will likely see a release within 95-105% for the reasons listed below. If you are seeing more than 105% release you might be making mistakes in sample and standard prep/analysis or there might be interference with analysis of the active drug (in your case folic acid; aka, your method is not specific for the drug and there is something in your matrix or solvents to interfere). A common source for results above 100% is also using reference standard that has its purity incorrectly compensated for %water; check the certificate for purity clarifications such as "on anhydrous basis" or "dried basis" which would indicate you need to run titration or loss on drying prior to use.

For example, if your film was supposed to be 100.00 mg with 5.00 mg dose of folic acid, chances are the actual drug load was in some reasonable range like 4.90 - 5.10 mg instead of the target 5.00 mg. That's because of normal variations in handling, weighing, process losses, unaccounted purity and % water of the starting material, etc. Then your analytics have normal variations in reproducibility (%RSD), accuracy (%recovery), and normal lab errors in standard preparations. Just like above, if you make an analytical standard with theoretical 5.00 mg/mL, it will end up being around there but not truly that exact number. Add to that errors in volumetric labware such as volumetric cylinders, flasks, pipettes, and the volumes and pH+salinity (if any) used for the dissolution medium for the drug release, and you end up with multiple points where variability is introduced.

Even if your manual work and instrumentation is all performing as it should, those normal errors and variations cannot be fully omitted and they will add up.

In addition to drug release, it's beneficial to run Content Uniformity to check the actual drug content (folic acid) in 10 doses (films) of the batch. For drug release we often calculate against the theoretical drug load but as we said above, that theoretical value is not always exact (that part about 5.00 mg in theory vs 4.9 - 5.1 mg).

Cumulative drug release, which is the total amount of drug released from a dosage form over a specified period, should not exceed 100% in the case of folic acid or other drugs. This is because it suggests a problem with the experimental setup, data analysis, or possibly errors in measurement. However, in some cases, analytical errors or variations in experimental conditions may lead to inaccuracies in measured drug release values. To avoid such scenarios, it is crucial to review experimental procedures, ensure accurate sample collection and analysis, rule out potential sources of error, consult relevant literature, and seek advice from experts in the field.