Can Hach advise on how deviations from the method procedure will impact results?

Document ID

Document ID TE9478

Version

Version 1.0

Status

Status Published

Published Date

Published Date 03/06/2018
Question
Can Hach advise on how deviations from the method procedure will impact results?
Summary
Importance of following method documentation and scope of support.
Answer
Often questions arise on how certain deviations from the method document will impact results. Almost all method documents include a method performance section which often states something similar to "The method performance data that follows was derived from laboratory tests during ideal test conditions. Users can get different results under different test conditions." before providing a precision statement for the method. In summary, assuming ideal test conditions and that this method document is followed exactly when performing the test, the error in the result obtained is expected to be within the tolerance provided with 95% confidence. Any deviation from the test method invalidates this statement. Hach cannot guarantee results obtained when the method documentation isn't followed as written.

This does not mean the same thing as saying that result will not be accurate if a deviation is made, just that Hach cannot advise on the accuracy or precision of results obtained with a deviation from the method document. A primary standard can be ran to verify that results obtained on the standard using a method which is deviated from the method document still falls within what would be considered an acceptable tolerance. This tolerance is something that would also need to be determined by the end user for themselves. This process is not supported by Hach, and the recommendation would instead be to follow the method document as written while making no deviations.

In regards to regulatory compliance, compliant methods are compliant as written. Any deviation from the written method may invalidate results and make them no longer reportable. Check with a regulator on if results obtained with methods which are deviated from the method documentation are reportable.

Examples of deviations from the method include but are not limited to:
  • Adding additional steps to the test procedure that not included in the method.
  • Skipping steps of the test procedure.
  • Using different products to the ones listed in the required reagents section.
  • Adding additional pretreatment performed on samples.
  • Not following the sample collection and storage section.
  • Not using the appropriate adapters or samples cells listed in the instrument specific information section.
  • Using the method for sample types not listed in the scope and application section.
  • Not performing the test on an instrument listed in the instrument specific information.
  • Not using the pre-programmed calibration curve selected with the program number provided in the test procedure for colorimetric methods.
  • Performing the steps of the procedure in a different order.
  • Not waiting the full wait times, or waiting for longer than the wait times listed.

Was this answer helpful?

Submitting...
Thank you for your feedback!
There was an error with your submission. Please try again.