What can be done if the sample has a lot of color or turbidity before any alkalinity reagents are added, therefore the color change is not seen?

Document ID

Document ID TE100

Published Date

Published Date 25/01/2018
Question
What can be done if the sample has a lot of color or turbidity before any alkalinity reagents are added, therefore the color change is not seen?
Summary
Measuring alkalinity in turbid or colored samples.
 
Answer
If the endpoint is not easily seen because the sample is turbid or colored, it is possible to measure the endpoint using a pH meter.

Set the pH meter to measure continuously and stop adding the titrant when the pH of the samples reaches the desired endpoint as detailed in the Water Analysis Handbook (WAH).

For total alkalinity, the pH is generally around pH 4.5. For phenolphthalein alkalinity, the pH is generally around pH 8.3. There is no need to filter the sample if measuring the endpoint with a pH meter.

Alkalinity, Phenopthalein and Total Method 8203
Alkalinity, Phenopthalein and Total Method 8221 BT