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

Instruction Manual Silver/Silver Sulfide Electrode
7
7. Read the electrode slope according the meter manufacturer's instructions. Correct electrode
operation is indicated by a slope of 90-100%. See the
TROUBLESHOOTING
section if the
slope is not within this range.
MEASUREMENT
Measuring Hints
All samples and standards should be at the same temperature for precise measurement. A difference
of 1
o C in temperature will result in about a 2% measurement error.
Constant, but not violent, stirring is necessary for accurate measurement. 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.
All silver samples and silver standards should be stored away from light.
Always dilute sulfide samples with SAOB (1:1) when they are collected.
Always rinse the electrodes with distilled water and blot dry between measurements. Use a clean,
dry tissue to prevent cross-contamination.
A slow-responding electrode may point to deposits on the membrane. Use polishing paper to
remove such deposits. See the section on
Electrode Response
.
For low level silver measurements, use labware made of plastic.
For samples with high ionic strength, prepare standards whose composition is similar to the sample.
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 cement bonding the sensing crystal to the electrode body. Infrequent measurements in
solutions containing methanol, benzene, or acetone are permitted. Please check with Eutech
Instruments Pte Ltd. before using the electrode in other organic solvents.
The temperature of the standard solution and of the sample solution should be the same and below
80oC.
Samples containing sulfide must be buffered with SAOB to convert HS-
1
and H
2
S to S
-2
.
Samples containing silver must be below pH 8 to avoid reaction with OH
-1
. Silver samples should
be acidified with 1M HNO
3
, if necessary.