What can cause phenol red to turn yellow in the bottle?

Document ID

Document ID TE7157

Version

Version 1.0

Status

Status Published

Published Date

Published Date 13/03/2017
Question
What can cause phenol red to turn yellow in the bottle?
Summary
Phenol red contamination
Answer
Phenol red is a pH indicator that is yellow at a pH below 6.8 and red at a pH above 7.4 with varying shades from yellow to red between those pH levels. If the indicator has turned yellow in the bottle this means it has become contaminated with something that has made the pH more acidic and brought the pH below 6.8.

This can impact the following products:
Phenol Red Indicator Solution, Spec. Grade, 50 mL (Catalog Number/Order Code 2657512)
Phenol Red Indicator Solution, 100 mL MDB (Catalog Number/Order Code 21132)
Phenol Red Indicator Solution, 50 mL SCDB (Catalog Number/Order Code 21126)
Phenol Red Indicator Solution, 15 mL SCDB (Catalog Number/Order Code 21136)
Phenol Red Indicator Solution, 500 mL (Catalog Number/Order Code 21149)