Understand the relationship
The reasoning behind the result
Convert a response scale into a concentration scale
σconcentration ≈ σresponse/|slope|
A steeper calibration changes signal more for each concentration increment. Dividing response variability by the magnitude of that slope translates the signal scale into concentration units. The selected multipliers then define the reported scenarios.
The sign of a decreasing calibration does not create a negative detection estimate. The magnitude of slope is used, while a zero slope is rejected because it cannot translate signal differences into concentration differences.
Choose the variability source deliberately
The response SD might come from an appropriate blank study, calibration residuals or another justified estimate. The entered-SD mode preserves that external choice. The blank mode calculates ordinary sample SD and displays the number of observations.
Two readings permit the arithmetic but do not establish that the study is adequate. If all blanks are identical, the calculated SD is zero; that does not establish a physically zero detection limit.
An estimate still needs confirmation
The model does not assess accuracy or precision at the estimated concentration, matrix effects, false-positive behavior or the suitability of the chosen calibration interval. These properties require an appropriate experiment.
Multipliers such as 3.3 and 10 are shown only as explicitly entered examples of an SD/slope calculation. No method, jurisdiction or regulatory acceptance is selected automatically.
Follow the numbers
Track the units through both estimates
- Response SD is 0.01 signal units and slope is 0.2 signal units per µg/mL.
- The translated scale is 0.01/0.2 = 0.05 µg/mL.
- With entered multipliers 3.3 and 10, estimates are 0.165 µg/mL and 0.5 µg/mL respectively.
The multipliers and SD source remain part of the result's meaning; the numerical outputs alone do not validate an assay.
Quick guide
How to use this calculator
- Choose an externally established response SD or enter matching blank replicates.
- Enter the linear calibration slope in signal per concentration unit.
- Enter the multipliers required by your chosen approach.
- Treat the outputs as estimates that require experimental confirmation, not automatic validated method limits.
Calculation method
Calculation and interpretation
Make the response variability, calibration sensitivity and chosen multipliers behind a detection-limit scenario explicit.
Detection estimate = kd × σresponse / |slope|; quantitation estimate = kq × σresponse / |slope|
Worked example
Track the units through both estimates
The multipliers and SD source remain part of the result's meaning; the numerical outputs alone do not validate an assay.
Detection estimate = kd × σresponse / |slope|; quantitation estimate = kq × σresponse / |slope|
Supported inputs
Precision and limits
Experimental boundary
This workbench reconciles entered measurements or plans. It does not validate an assay, establish biological effects or replace the protocol and controls for the actual experiment.
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