MDC / MDA
Minimum detectable activity calculator
Model-based estimate. Use the stated geometry, composition and measurement assumptions; see the tool scope for limitations.
Input
Instrument statistics and calibration factors
Counter/scaler starting point for a liquid sample counted by volume.
Calculation mode
When entered, the calculator compares net counts against Lc and Ld.
Instrument / certificate snapshot
Saved with the calculation; it does not change the formula unless the numeric inputs above are changed.
Result
Counter / scaler MDC
0.777833 Bq/L
- MDA
- 0.777833 Bq
- Lc
- 56.9845 counts
- Ld
- 116.675 counts
- Background
- 600 counts
- Count time
- 600 s
Formula
Lc = k·√(2B)Ld = k² + 2k·√(2B) (Currie, paired blankk = 1.645 → 2.71 + 4.65·√B)MDA = Ld / (eff·yield·t). No chemical-yield/aliquot correction — for prepared samples the MDA is underestimated.Statistical detection-limit modelCurrie-style decision threshold and detection limit arithmetic.No radionuclide database is used; efficiency/yield/background are user or instrument inputs.Screening estimate — result depends on the chosen procedure, count/sample time, geometry, efficiency, yield and instrument calibration; it does not replace a validated laboratory method.
- MDA/MDC is a statistical screening calculation; verify against the lab procedure, detector calibration and applicable regulatory method.
- Efficiency, yield/abundance, background and sample geometry must come from instrument-specific calibration or procedure data.
- Counter/scaler mode assumes a single background estimate and constant counting efficiency for the sample geometry.