How do I calculate ELISA sample concentrations from a standard curve?

Subtract the blank from every optical density, fit a 4PL or 5PL model to the standard series, then interpolate each sample OD on the inverse of the fitted curve. Labreador does this in the browser and flags values outside the LLOQ/ULOQ range as extrapolated.

What is the difference between IC50 and EC50?

EC50 is the concentration producing 50% of the maximal response for a stimulatory curve; IC50 is the concentration causing 50% inhibition. Both come from the same 4PL/5PL fit — only the direction of the response differs.

How is relative potency determined in a parallel line analysis?

Fit reference and test curves with shared slope and asymptotes, verify parallelism with an F-test, then take the horizontal shift between the curves on the log-dose axis. Relative potency (%) is 10^(log EC50 reference − log EC50 test) × 100.

How do I know if my ELISA assay is valid?

Check the R² quality tier, residual pattern, back-calculated standard recovery (typically 80–120%), replicate CV%, the OD span between top and bottom standards, and whether the EC50 falls inside the standard range. Labreador reports all of these in its Method Health panel.

Which ecotoxicology indices can be computed for trace elements?

Estimated daily intake (EDI), target hazard quotient (THQ), hazard index (HI), contamination factor (CF), pollution load index (PLI), geoaccumulation index (Igeo), enrichment factor (EF), bioaccumulation factors (BAF/BSAF) and biometric indices such as Fulton condition factor.

Labreador — Free ELISA, IC50 & Ecotox Analysis

Choose Analysis Module

Select the type of bioassay analysis you want to perform

New here? See how every calculation works — formulas for ELISA curves, IC50/EC50, relative potency and ecotoxicology indices, or start with the free ELISA calculator.

Labreador — Bioassay Analysis Platform

Choose Analysis Module

ELISA Analysis

Dose-Response / IC50

Ecotoxicology

Kinetic Analysis

PLA / Relative Potency

Latest from the blog

How to Calculate Km and Vmax: A Practical Enzyme Kinetics Guide

4PL vs 5PL for ELISA Standard Curves: Why Log-Linear Regression Fails