1. What is Inverse Isotope Dilution Analysis (IIDA)?

Definition: IIDA is an analytical technique used to determine the quantity of an active (radioactive) compound by mixing it with a known amount of inactive isotope of the same compound.

Purpose: This method is particularly useful in radiochemistry, environmental science, and pharmaceutical research for quantifying radioactive substances.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( x' \) — Unknown amount of active compound (kg)
• \( y' \) — Amount of inactive isotope of same compound (kg)
• \( S_f \) — Specific activity of mixed compound (Bq/kg)
• \( S_i \) — Specific activity of pure labelled compound (Bq/kg)

Explanation: The formula calculates the unknown radioactive quantity based on the change in specific activity when mixed with a known quantity of inactive material.

3. Importance of IIDA

Details: This technique is crucial for accurate measurement of radioactive substances in complex matrices where direct measurement might be difficult.

4. Using the Calculator

Tips: Enter the amount of inactive isotope (must be > 0), specific activity of the mixed compound, and specific activity of pure labelled compound (must be > mixed compound activity).

5. Frequently Asked Questions (FAQ)

Q1: What units should I use for input?
A: Use kilograms (kg) for mass and becquerels per kilogram (Bq/kg) for specific activities.

Q2: Why must Si be greater than Sf?
A: The pure compound must have higher activity than the mixture; otherwise the calculation would give negative or infinite results.

Q3: What if I get extremely small numbers?
A: This is normal when working with radioactive substances which are often active at very small quantities.

Q4: Can I use this for non-radioactive isotopes?
A: No, this method specifically relies on measuring changes in radioactivity.

Q5: How accurate is this method?
A: Accuracy depends on precise measurement of specific activities and the purity of the inactive isotope.