LaMotte SMART Spectro Spectrophotometer - Manual (Page 195)

APPLICATION: Drinking, surface, and saline waters; swimming pool water;
domestic and industrial wastes.
METHOD: The various pH indicators exhibit a specific color change
over a narrow pH range. The color changes are measured
colorimetrically.
SAMPLE
HANDLING &
PRESERVATION: Sample should be analyzed immediately after collection.
INTERFERENCES: 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.
INDICATOR,
RANGE,
& TEST NAME:
pH Indicator pH SMART Spectro
Test Name
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
PROCEDURE
Use universal sample holder.
1. Use Indicator, Range, & Test Name chart to select the indicator,
corresponding to anticipated pH range and to determine corresponding
test name to select from spectrophotometer menu.
2. Press and hold
ON button until spectrophotometer turns on.
3. Scroll to and select PROGRAMMED TESTS.
4. Scroll to and select ALL TESTS (or another sequence containing the
appropriate pH test name) from TESTING MENU.
5. Scroll to and select the appropriate pH test name from menu.
6. Rinse a clean tube (0290) with sample water. Fill to the 10 mL line with
sample.
7. Insert tube into chamber, close lid and select SCAN BLANK.
8. Remove tube from Spectro. Use the 0.5 mL pipet (0369) to add exactly 0.5
mL of the pH indicator for the chosen range. Cap and mix.
9. Insert tube into chamber, close lid and select SCAN SAMPLE. Record
result.
10. Press
OFF button to turn spectrophotometer off or press EXIT button to
exit to a previous menu or make another menu selection.
pH 2/2 SMART SPECTRO TEST PROCEDURES 05.04