CDP & Dissolution Profile — Concept & Beginner Guide

The first thing the calculator asks is what you want to calculate. The answer decides which setup block you see, so it is worth getting right before you type anything.

The two single-product modes are independent of each other and of Comparative mode. Each has its own dilution factor, potency, label claim, factor, standard weight and standard readings. Nothing you type in one mode carries into another.

Every unit you enter, one area or one absorbance reading, is converted to a percentage of label claim using this calculation:

Standard potency is entered as a percentage (for example 99.8), which is what makes the answer a percentage. The Factor is optional. Leave it blank and it counts as 1. A blank, zero or negative factor is treated as 1.

A single-unit example

Take five standard readings of 1253100, 1255400, 1254900, 1254200 and 1254000. Their average is 1254320. The settings are standard weight 20.5 mg, dilution factor 20, potency 99.8%, label claim 500 mg and no factor. These are made-up numbers to show the arithmetic, so use the dilution factor your own protocol gives you. A unit that reads an area of 1226700 gives:

Had the factor been 1.02 instead of blank, the same unit would give 81.63%. The calculator recalculates every % cell immediately whenever any of these settings change, and also refreshes a result you have already calculated.

Same Day or Different Days?

Choose Same Day when one standard solution served both products. One standard weight and one set of readings then apply to every Reference and Test unit. Choose Different Days when each product was run on its own day with its own standard. You then enter a standard weight and a set of standard readings for each product. In both cases the dilution factor, potency, label claim and factor remain shared, because they describe the method, not the day.

Each product panel, at each time point, has an optional Covering Standard section. It is for extra standard injections run between sample injections, for instance every 6 to 12 units. It starts closed and shows a counter once you add readings.

Two numbers are produced and they are calculated differently:

• Combined average is the average of the two group averages. The System Suitability average and the covering average each count once, regardless of how many readings are in each. This is the figure used as the standard response in the % Result.
• Combined %RSD pools every individual reading from both groups into one set and calculates the usual %RSD on it.

For example, with the five readings above and two covering readings of 1258200 and 1257800, the System Suitability average is 1254320, the covering average is 1258000, and the combined average is 1256160. A plain average of all seven readings would have been 1255371, so the two methods give different standard responses. The pooled %RSD of the seven readings is 0.1544%. Each panel shows a small table with the System Suitability, Covering Standard and Combined rows so you can see exactly what is being used.

Each time point is its own block with a minutes field. In Comparative mode the block holds a Reference panel and a Test panel, each starting with 12 unit rows. Add or remove units if your study differs. For every panel the calculator shows the mean %, the minimum and maximum, the SD (sample SD, dividing by n − 1) and the %RSD.

• Every added row must be filled. Empty standard readings, covering readings or unit rows stop the calculation. The first empty box is scrolled into view and outlined. Fill it or remove the row with the ✕ button.
• Every block needs its time in minutes. Blocks are sorted by time automatically, so you can add them in any order.
• At least one time point is needed, with data on both sides in Comparative mode.
• Means use full precision. The displayed rounding never feeds back into mean, SD, %RSD or f₂.

f₂ compares the mean % Result of the Reference (Rt) and Test (Tt) at each time point:

Here n is the number of time points used. The calculator follows exactly the four stages shown in its math log: sum the squared differences, divide by n, add 1 and take the square root, then apply the logarithm.

Worked example

1. Sum of squared differences = 10.89 + 17.64 + 13.69 + 9.61 + 3.61 = 55.44
2. Divide by n: 55.44 ÷ 5 = 11.088
3. Add 1: 12.088. Square root: 3.4768
4. 100 ÷ 3.4768 = 28.7622. log₁₀ of that is 1.4588. Multiply by 50: f₂ = 72.94

72.94 is inside 50 to 100, so the banner reads Dissolution Profiles: SIMILAR. Had the Test run been much lower, say 18.0, 30.5, 45.0, 62.0 and 80.0 against the same Reference, f₂ would fall to about 41.43 and the banner would read NOT SIMILAR.

What the calculator does and does not decide for you

• Fewer than 3 time points: f₂ is still shown, but the banner says there are too few time points for regulatory use, in place of similar or not similar.
• 15 minutes: if one block is at exactly 15 minutes and both products are at 85% or higher, that row is highlighted green and a note explains that f₂ is then not required. The f₂ value is still calculated.
• 85% limit on points: the calculator does not remove any point. Every time point you enter goes into f₂. Keep to your protocol's rule on how many points at or above 85% may be included.
• %RSD limits: they are not enforced. Look at the %RSD of each time point and judge it yourself.

Single-product mode ends with a profile table: time point, mean %, min %, max %, SD and %RSD. Below it there is an optional f₂ table. It opens with your own product's time points and means already filled in, and the other product's column empty.

• Type the other product's % Result for every time point. Every cell can be edited, and you can add or delete rows.
• Each row needs a time point and both values. A row missing either is reported, and duplicate time points are rejected.
• At least 3 rows are required. With fewer, f₂ is not calculated.
• Pressing the f₂ button fills the (Rt − Tt) and (Rt − Tt)² columns and shows the running sums under the table.

The same f₂ maths is used here as in Comparative mode.

On screen

A comparative result shows the table of Rt, Tt, difference and squared difference, the f₂ banner and cards, a chart of % Result against time, and a four-step math log. Single-product results show the profile table and chart. The chart is drawn directly on the page, so no extra file loads.

Copy Report

The copy button puts a plain-text summary on your clipboard: the time points compared, each row's Rt, Tt, difference and squared difference, the sum, the f₂ value and its interpretation. Single-product mode copies the profile table with mean, min, max, SD and %RSD for each time point.

Print Report

The print report only opens after you have calculated. It includes the working standard details, the standard readings (one table for Same Day, two side by side for Different Days), and one page per time point with unit-level tables that carry the average, min, max and %RSD rows, followed by the covering standard readings and the combined figures. The comparison section and f₂ come last. Values follow your Decimal Places choice.

You can add a company logo to the report. It has to be a PNG, JPG or WebP image, no larger than 1 MB and between 30 × 30 and 512 × 512 px on each side. The image is processed in your browser, and HEIC photos from phones are not accepted. Esc closes the preview.

• Mixing standards from different days under Same Day. The weight and readings you enter apply to both products. If they were not prepared together, choose Different Days.
• Typing potency as 0.998. Enter 99.8. A fraction makes every % Result about a hundred times too small.
• Using the wrong label claim. It is mg per unit, not the total in the dissolution vessel.
• Leaving a faulty reading in the standard set. One bad standard injection shifts the average and every % Result with it. Check the %RSD shown under the readings.
• Entering too many points above 85%. The calculator will not stop you, but your protocol may.
• Mixing time points. Reference and Test must be at the same times, and each time can be used once only in the f₂ table.
• Changing the settings after calculating and forgetting the report. Results refresh automatically, but always open the print report after your last change.

How does the CDP calculator work out the % Result for each unit?

For every unit it multiplies the unit's area or absorbance by the standard weight, the dilution factor, the standard potency and the optional factor, then divides by the average standard response multiplied by the label claim. The potency is typed as a percentage, so the answer comes out directly as a percentage dissolved. The average standard response comes from your System Suitability readings, combined with any covering standard readings added to that panel.

When is f₂ calculated, and what does the calculator do with fewer than 3 time points?

In Comparative mode, f₂ is calculated when you press the calculate button. If you entered fewer than 3 time points, the number is still shown, but the result banner says there are not enough time points for regulatory use instead of declaring the profiles similar or not similar. In the f₂ table of the single-product modes, fewer than 3 usable rows stops the calculation with a message.

Does the calculator leave out time points after 85% dissolution?

No. Every time point you enter is used in f₂. The 85% information is shown only as a note and, at 15 minutes, as a green highlight when both products are at or above 85%. If your protocol allows only one mean value at or above 85% per product in the f₂ calculation, enter only the points you are allowed to use.

Does the calculator enforce the %RSD limits for the means?

No. It shows the SD and %RSD of the units at each time point for you to judge. The commonly quoted limits (20% for the earliest points and 10% for later ones) are listed on the calculator page for reference, but the tool does not block or flag a time point for exceeding them. Check each time point against your protocol before you rely on the means.

What is the difference between Same Day and Different Days?

Same Day means one standard was prepared and injected for both products, so one standard weight and one set of System Suitability readings feed both Reference and Test. Different Days means each product has its own standard weight and its own readings. Dilution factor, potency, label claim and factor stay shared in both cases.

Why does the calculator ask me to choose Same Day or Different Days before calculating?

Because it has no default. The standard weight and readings that go into every % Result depend on that choice, so the calculator stops with a message until you pick one. This applies only to Comparative mode; the Test-only and Reference-only modes have their own separate setup blocks.

How are the Covering Standard values combined with the System Suitability readings?

The combined average is the average of two group averages: the System Suitability average and the covering standard average, each counted once. The combined %RSD is different. It pools every individual reading from both groups and calculates the ordinary %RSD on that single set. The two numbers come from two different calculations, so do not expect one to be derived from the other.

What does the Decimal Places setting change?

It changes only what is displayed, from 1 to 5 digits, and the same setting is used in the copy text and the printed report. Calculations keep full precision underneath, so the f₂ value does not drift when you change the display.

Can I get f₂ if I only have one product's data in the calculator?

Yes. After calculating a Test-only or Reference-only profile, an optional table opens with that product's time points and means pre-filled. You type the other product's % Result for each time point, and the calculator works out f₂ from the table. Each row needs a time point and both values, time points must be unique, and at least 3 rows are required.

What do I need to fill in before the Print Report button works?

You must complete a calculation first. In Comparative mode, calculate the comparative profile. In a single-product mode, calculate that product's profile, and calculate the f₂ table as well if you want f₂ on the report. If nothing has been calculated yet, a message asks you to do so.

Educational use only. This guide explains how the CDP calculator on this site works. It is not a validated system and does not replace your SOPs or the guidance your regulator expects you to follow. Please read the disclaimer for how this site should be used.