Why are the fluoride results lower than those determined by an outside lab?

Document ID

Document ID TE356

Published Date

Published Date 27/05/2017
Question
Why are the fluoride results lower than those determined by an outside lab?
Summary
Fluoride results not matching an outside lab
Answer
There are several possible reasons for this.

-The outside lab may be using a different method to measure Fluoride.
-There could be interferences in the sample causing inaccuracy of the colorimetric test.
- There could be fluoride contamination in the water used for the SPADNS blank. If there is any fluoride contamination in the blank, the color difference between the blank and sample will be less than it should be, and results will be low.

Determine what type of test the outside lab is performing and whether a distillation is being performed on the samples in order to better compare.