eutech-instruments lead epoxy Manual Do Utilizador

3. 

Adjust the meter to the concentration of the standard and fix the value in the memory 
according to the meter manufacturer's instructions. 

 
4. 

Rinse the electrodes with distilled water and blot dry. 

  
5. 

To another 150 ml beaker, add 50 ml of methanol-formaldehyde solution and 50 ml of the 
higher value standard. Add 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 

 

sections if the slope is not within this range. 

 
 

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

o

C in temperature will result in a 4% 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 insulation material, such as styrofoam sheet, between the stirrer and beaker. 
 
Use plastic lab-ware for all low level measurements in order to minimize absorption on container 
walls. Always rinse the electrodes with distilled water and blot dry between measurements. Use a 
clean, dry tissue to prevent cross-contamination. 
 
To prevent oxidation of the membrane, always use methanol-formaldehyde solution to mix with all 
standards and samples. 
 
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. 
 

 
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 Eutech Instruments Pte Ltd. before using these electrodes in 
other organic solvents.