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Dissolution Calculator: % Dissolved, Release Profile & f2
Work out % dissolved for each tablet or capsule and check it against the Q-value acceptance table (stages S1, S2 and S3), build a release profile with the volume-replacement correction, and compare two profiles with the f2 similarity factor. Free, no sign-in, with a printable record.
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How it works
% dissolved = (Aᵤ ÷ Aₛ) × standard conc. × further dilution × medium volume ÷ label claim × 100
With replacement: amount at pull n = Cₙ × V + v × (C₁ + … + Cₙ₋₁)
Without replacement: amount at pull n = Cₙ × (V − (n−1)v) + v × (C₁ + … + Cₙ₋₁)
f2 = 50 × log₁₀ {100 ÷ √[1 + Σ(R − T)² ÷ n]}
Each sample you withdraw takes drug out of the vessel. Without the correction, later time points are under-reported; the calculator adds back the drug removed in earlier pulls.
Acceptance table (immediate-release)
| Stage | Units tested | Acceptance |
|---|---|---|
| S1 | 6 | Each unit not less than Q + 5 % |
| S2 | 6 more (12 in all) | Average of 12 ≥ Q, and no unit less than Q − 15 % |
| S3 | 12 more (24 in all) | Average of 24 ≥ Q, not more than 2 units less than Q − 15 %, and no unit less than Q − 25 % |
This is the harmonised acceptance table used by the USP and other pharmacopoeias for immediate-release products. Always check the Q value and any special criteria in your monograph.
Worked example
500 mg tablet, 900 mL medium, UV
Standard: 25.0 mg (purity 99.5 %) in 500 mL = 0.04975 mg/mL, absorbance 0.512. Sample filtered, 5 mL diluted to 50 mL (further dilution 10), absorbance 0.550. % dissolved = 0.550 ÷ 0.512 × 0.04975 × 10 × 900 ÷ 500 × 100 = 96.2 %. With Q = 80 %, S1 needs every unit at 85 % or more.
Frequently asked questions
What is Q in dissolution?
Q is the amount of active ingredient, as a percentage of the label claim, that must be dissolved in the time given in the monograph – for example “not less than 80 % (Q) in 30 minutes”. At stage S1 every unit must reach Q + 5 %.
Do I always need the volume-replacement correction?
Only when you take more than one sample from the same vessel. With a single time point there is nothing to correct. With several pulls, the correction is needed whether or not you replace the medium.
When is the f2 similarity factor used?
To compare the dissolution profile of a test product with a reference, e.g. for a generic or after a change in formulation or site. An f2 of 50–100 means the profiles are similar. Use 12 units per product, leave out time zero, and use only one time point above 85 % (the calculator follows FDA/WHO or EMA, as you choose). If both release 85 % or more within 15 minutes, f2 is not needed.
My results are above 100 %. Is that wrong?
Results of 100–105 % are normal for tablets with a little overage or within analytical variability. Values far above that usually mean a wrong dilution, standard weight or medium volume.