Preventing Contamination: Tweak your technique.

Calbiotech Immunoassay kits are easy to use, stable and reliable kits. Each kit comes with a package insert that is short and so vividly written that even a new ELISA user (technician) can comfortably perform the assay with a great accuracy and success. Nevertheless, like any other analytical measurement methods, ELISA is also susceptible to some contamination if we do not handle the reagents and/or instruments properly.

Today we will look at some common contamination which can occur during simple assay performance and ways to prevent them.

Cross-Contamination and Prevention

Sample-to-sample (carry-over)

In an assay involving multiple samples, remnants of sample A, after delivery, can mix with the subsequent sample B. This cross-contamination between samples may cause a pseudo positive test result.


  • Change the tip after each sample.


Contaminated tips and/or a contaminated pipette can contaminate samples.


  • Change the tip after each sample.
  • Only use new or sterilized pipette tips.
  • If you think the source of contamination is the pipette, clean or autoclave the parts of the pipette which are in contact with the sample.


Contamination can occur if sample or any other fluid is allowed to enter the cone of the pipette.


  • Keeping the pipette vertical during pipetting can prevent liquids from running into the pipette body. Avoid inclining your pipette excessively.
  • Always store the pipette vertically.
  • Release the plunger slowly to prevent samples from jumping into the cone of the pipette.


During assay performance, the washing step in the assay procedure is very critical. It is very possible that wells can cross-talk between each other. Make sure you consider the following points:


  • Do not over fill the wells with wash buffer during the washing step.
  • Clean your washing machine system (or bottle, if manual washing is used) regularly.
  • Use clean distilled or de-ionized water while diluting the concentrate wash buffer provided in Calbiotech ELISA kits.

We hope you found our quick note on preventing cross contamination useful. Please share anything you think we missed in the comment section of this blog.

For technical support with running any of our assays, please contact Calbiotech Customer Support and we will get back to you immediately.