Thermo Fisher Scientific Ion Selective Electrodes Copper - Manual (Page 7)

Instruction Manual Copper Electrode
7
MEASUREMENT
Measuring Hints
All samples and standards should be at the same temperature for
precise measurement.
Constant, but not violent, stirring is necessary for accurate
measurements. Magnetic stirrers can generate sufficient heat to
change the solution temperature. To counteract this effect,
place a piece of insulating material, such as styrofoam sheet,
between the stirrer and beaker.
Always rinse the electrode(s) with distilled water and blot dry
between measurements. Use a clean, dry tissue to prevent cross-
contamination.
For samples with high ionic strength, prepare standards whose
composition is similar to the sample. Dilute concentrated
samples (>0.1M) before measurement.
Use fresh standards for calibration.
Use 2 ml of ISA for each 100 ml of sample or standard.
Always check to see that the membrane is free from air bubbles
after immersion into the standard or sample.
Sample Requirements
All samples must be aqueous and not contain organics which can
dissolve the epoxy electrode body and/or the cement bonding the
sensing crystal to the electrode body. Infrequent measurements
in solutions containing methanol, benzene, or acetonitrile are
permitted. Highly polar solvents slowly attack the electrode.
Please check with before using these electrodes in other organic
solvents.
The temperature of the standard and of the sample solution should
be the same and below 80 degrees C. About a 4% error in the
slope will occur for each 1
o C difference in temperature.
Interferences should be absent. If they are present, use the
procedure found in the Interference and Electrode Response
sections to remove them.
Adjust sample pH with 1M HNO
3
to below pH 7 to avoid
precipitation of cupric hydroxide, Cu(OH)
2
.
Units of Measurement
Cupric ion concentrations are measured in units of parts per
million, moles per liter, equivalents per liter, or any other