eutech-instruments sodium glass Manuel D’Utilisation

Instruction Manual 

 

Sodium Electrode 

 

3

 
4. 

Rinse the electrodes with the electrode rinse solution and blot dry. 

5. 

To another 150 ml beaker, add 100 ml of the higher value standard and 2 ml of ISA.  
Place the beaker on a magnetic stirrer and begin stirring at a constant rate. Lower the 
electrode tips into the solution. 

 
6. 

Adjust the meter to the concentration of the standard and fix the value in the memory. 

 
7. 

Read the electrode slope according to the meter manufacturer's instructions. Correct 
electrode operation is indicated by a slope of 90-100%. See the 

 

section if the slope is not within this range. 

 
 

 
Measuring Hints 

All samples and standards should be at the same temperature for precise measurement, preferably 
ambient temperature. A difference of 1

o

C in temperature will result in about a 2% measurement 

error. The electrodes should not be used above 70

o

C. 

 
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 a styrofoam sheet, between the stirrer and the beaker. 
 
Always rinse the electrodes with electrode rinse solution from a wash bottle between 
measurements. Use a clean, dry tissue to prevent cross contamination. Never use distilled water. 
 
Store the electrodes in electrode storage solution between measurements. Do not store in air or 
distilled water. Always soak new electrodes overnight in electrode storage solution prior to first 
use. When making low level sodium measurements, use a dilute sodium chloride storage solution. 
Add 1  ml of ISA to 100 ml of dilute storage solution. 
 
Plastic lab-ware should be used for low level measurements (<1 ppm). All measurements should be 
made in basic solution. All samples and standards should be adjusted to a pH > 9 with ISA. 
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 standard or 
sample. 

 
Sample Requirements 

The sample measuring range is pH 9-12. Use the ISA recommended to adjust the pH for best 
accuracy. Make sure that the samples and standards are at the same temperature. The glass 
electrode sensing bulb will not be attacked by most organic solvents. 

 
Units of Measurement 

Sodium concentrations are measured in units of parts per million, equivalents per liter, moles per 
liter, or any other convenient concentration unit. Table 1 indicates some of the concentration unit 
conversion factors.