Standard Curve R² Below 0.98 Threshold (ELISA (Standard Curve Fit Problems))

Question

Accepted Answer

The regression coefficient (R²) of the standard curve falls below 0.98, indicating poor curve fit and unreliable quantification of sample concentrations. Common causes: 1) Standard protein has degraded due to improper storage or repeated freeze/thaw cycles 2) Pipetting errors during standard preparation or plate loading 3) Incorrect dilution of standard solution or calculation errors in serial dilution 4) Incomplete reconstitution of lyophilized standard with undissolved material remaining 5) High variation between replicate wells due to inconsistent mixing or pipetting technique Solutions: 1) Store standard according to manufacturer recommendations and avoid freeze/thaw cycles whenever possible 2) Use calibrated pipettes and ensure proper pipetting technique with consistent vertical pipette positioning 3) Verify all dilution calculations and follow manufacturer's dilution protocol exactly 4) Briefly centrifuge the standard vial before opening and inspect for complete dissolution after reconstitution 5) Mix all solutions by gently pipetting up and down before adding to the plate; run standards in duplicates or triplicates 6) Ensure adequate equilibration time for all reagents to reach room temperature before use