High Coefficient of Variation Between Standard Replicates (ELISA (Standard Curve Fit Problems))

Question

Accepted Answer

Duplicate or triplicate wells for the same standard concentration show high variability (CV >10-15%), compromising curve fit and confidence in quantification. Common causes: 1) Inadequate mixing of standard solution before dispensing into replicate wells 2) Inconsistent pipetting technique with variable tip immersion depth or dispensing angle 3) Air bubbles in pipette tips or wells interfering with accurate volume delivery 4) Uneven coating or washing of ELISA plate wells leading to differential binding 5) Temperature gradients across plate during incubation (edge effects) Solutions: 1) Mix standard solution thoroughly by pipetting up and down gently 5-8 times immediately before dispensing replicates 2) Use consistent pipetting technique: maintain vertical pipette orientation and consistent tip immersion depth 3) Inspect for and remove air bubbles from pipette tips before dispensing and from wells after dispensing 4) Tap plate gently on benchtop after adding reagents to dislodge bubbles 5) Place plate in center of incubator; avoid outer rows/columns if edge effects are suspected 6) Consider running standards in triplicates rather than duplicates to enable outlier detection