eutech-instruments sodium glass Manuel D’Utilisation

Instruction Manual 

 

Sodium Electrode 

 

7

8. 

On semi-logarithmic graph paper, plot the millivolt reading (linear axis) against the 
concentration (log axis) as in Figure 1. 

 
9. 

Rinse the electrodes with electrode rinse solution and blot dry. 

 
10.  To a 150 ml plastic beaker add 100 ml of sample and 1 ml of low level ISA. Place the 

beaker on the magnetic stirrer and begin stirring. Adjust the pH, if necessary, to above 9.  
Lower the electrode tips into the solution. After the reading has stabilized, record the mV 
reading and determine the concentration from the low level calibration curve. 

 
11.  Prepare a new low level calibration curve daily. Check the calibration curve every two 

hours by repeating Steps 3-8. 

 
 

Follow the procedure given for sodium measurements with an ion meter. Always use the blank 
correction procedure. Use plastic lab-ware for low level sodium measurement. 

 

Reproducibility 
 

Electrode measurements reproducible to 

±2% can be obtained if the electrode is calibrated every 

hour. Factors such as temperature fluctuations, drift, and noise limit reproducibility. Reproducibility 
is independent of concentration within the electrode's operating range. 

 
Interference 
 

Table 3 lists some common cations that, if present in high enough levels, will cause electrode 
interference and measurement errors or electrode drift when using the sodium ion electrodes. 

 

Most samples do not contain or contain very little of the cations shown in Table 3. The ammonium 
ion (NH

4

+

), found in the recommended ISA, will not result in an error if all samples and standards 

have the same level of ISA present. 
 
Electrode drift and slow response could indicate the presence of high interference from the ions 
listed. Soak the electrodes in electrode storage solution when this happens to restore proper 
response. See 

 section. 

 
TABLE 3: Levels of Interfering Ions Resulting in a 10% Error at Specified Levels of Sodium 
  
   Interference 

 

M 

 

M 

Li

+1

 

  5X10-

M   5X10-

3

M   5X10-

2

M           

 

K

+1

 

  1X10-

2

M   1X10-

1

M 

 

1M               

Rb

+1

 

  3X10-

1

M 

 

3M 

 

 

--               

NH

4

+1

 

  3X10-

1

M 

 

3M 

 

 

--               

Ag

+1 

  3X10-

9

M   3X10-

8

M   3X10-

7

M          

Tl

+1

 

  5X10-

2

M   5X10-

1

M 

 

--                

 

ppm 

Li

+1

 

  1.5 

ppm  15 

ppm  150 

ppm 

 K

+1

 

  17 

ppm  170 

ppm 

 1,700 

ppm