LaMotte SMART Spectro Spectrophotometer - Manual (Page 215)

APPLICATION: Drinking, surface, and saline waters; swimming pool
water; domestic and industrial wastes.
RANGE: The various pH indicators exhibit a specifi c color
change over a narrow pH range. The color changes are
measured colorimetrically.
METHOD: Sample should be analyzed immediately after collection.
SAMPLE HANDLING
& PRESERVATION:
Sample color and turbidity interfere with the colorimetric
pH measurement. Color interference may be removed
by standardizing the instrument with the original water
sample. Two drops of 0.1N sodium thiosulfate per 100
mL of sample will eliminate chlorine interference.
INTERFERENCES:
pH Indicator pH SMART Spectro
Test Range
Chlorphenol Red 5.0–7.0 74 pH CPR
Phenol Red 6.6–8.4 75 pH PR
Thymol Blue 8.0–9.5 76 pH TB
pH SMART Spectro Test Procedures 2.11
Test P
rocedures