How should a negative result on a colorimetric test be interpreted?

Document ID

Document ID TE1585

Published Date

Published Date 27/05/2017
Question
How should a negative result on a colorimetric test be interpreted?
Summary
Negative values on a colorimetric test.
Answer
A negative result on a colorimetric test is not necessarily something to worry about and may indicate the following:

1) The analyte concentration may be below the detectable limit of the test. In this case, the negative value that is displayed is simply noise.

2) The sample is not compatible with the method.

In either case, it is advisable to test a standard solution to verify the accuracy and performance of the instrument, reagents, and lab technique.

Assuming good values are obtained when testing a standard, a sample spike (standard addition) would be a good way to verify if the sample is compatible with the method of interest.