Thermo Scientific
ROSS Ultra, ROSS Ultra Triode and ROSS pH Electrodes
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9
Thermo Scientific Orion
and water saturated with KCl. The ratio of methanol to water should be
similar to the sample composition. For tips on measuring pH in non-
aqueous samples, see Thermo Scientific Water Analysis Instruments
Application Note 007.
If using the 8220BNWP ROSS micro pH electrode, great care must
be taken to thoroughly rinse out the reference chamber and junction
before changing the reference solutions.
Measuring Hints
•
Always use fresh buffers for calibration. Choose buffers that are one
to four pH units apart.
•
Check the electrode slope daily by performing a two buffer
calibration. The slope should be 92 to 102%.
•
Except as noted in the
Sample Requirements
section, only use
ROSS fill solution, Cat. No. 810007. Do not use any fill solution that
may contain silver.
•
If a refillable electrode is used, always remove the fill hole cover
during measurements to ensure a uniform flow of fill solution.
•
If a ROSS Ultra Triode is used, immerse the electrode at least 2
inches (5 cm) in solution for best temperature response.
•
Between measurements, rinse the electrode with distilled water and
then with the next solution to be measured.
•
Stir all buffers and samples at a uniform rate.
•
Place a piece of insulating material, such as polystyrene foam or
cardboard, between the magnetic stir plate and beaker to prevent
measurement errors from the transfer of heat to the sample. Since
ROSS electrodes respond quickly to temperature changes, pH
changes due to temperature variations will be noticed.
•
To reduce the chance of error due to polarization, avoid rubbing or
wiping the sensing bulb. Use a lint-free tissue and gently blot the
sensing bulb.
•
If a refillable electrode is used in dirty or viscous samples or
the electrode response becomes sluggish, empty the electrode
completely and hold the junction under running water. Empty any
water from the electrode and refill it with fresh ROSS fill solution.
For a thorough cleaning method, refer to the
Electrode Cleaning
Procedures
section.
•
If a Sure-Flow electrode is used in dirty or viscous samples or
the electrode response becomes sluggish, empty the electrode
completely and hold the junction open under running water. Empty
any water from the electrode and refill it with fresh ROSS fill
solution. Press down on the electrode cap to let a few drops of the
ROSS fill solution flow out of the electrode and then replenish any
lost solution. For a thorough cleaning method, refer to the
Electrode
Cleaning Procedures
section.
•
Handle the 8220BNWP ROSS micro pH electrode with care. Do
not touch the pH bulb and stem against the bottom or walls of the
sample containers.
