eutech-instruments carbon dioxide gas User Manual

Instruction Manual 

 

Carbon Dioxide Electrode

 

 

19

"Incorrect Answer"         

incorrect scaling        

 

plot millivolts on the linear 

(but calibration             

of semi-log paper   

 

 

axis. On the log axis, be sure   

curve is good)                        

                              

 

concentration numbers within 

                                                 

 

 

 

 

each decade are increasing 

                                                 

 

 

 

 

with increasing concentration 

 
                           

 

incorrect sign         

 

 

be sure to note sign of millivolt 

                                                                                    

 

value correctly 

 
                           

 

incorrect standards      

 

prepare fresh standards 

                                                
                           

 

wrong units used         

 

apply correct conversion factor: 

                                                                                          

 

10

-3

M = 44 ppm as 

                                                 

 

 

 

 

CO

2

 = 100 ppm as CaCO

3 

                                                                                                 
                           

 

buffer added to          

 

add same standards 

 

 

    standards 

and 

not 

  proportions 

of 

 

                           

 

samples                

 

 

buffer to standards and samples 

 
                           

 

sample carryover         

 

rinse electrodes thoroughly 

                                                                                         

 

between samples 

 
If the electrode slope is found to be low during operation, the following solutions will be necessary 
to check the inner body: 
 
- pH 4 Buffer (0.1M NaCl added) 
Add 2.9 grams of reagent-grade NaCl to 500 ml of pH 4 buffer. Dissolve the solid. The solution  
may be stored for repeated use. 
 
- pH 7 Buffer (0.1M NaCl added) 
Add 2.9 grams of reagent-grade NaCl to 500 ml of pH 7 buffer. Dissolve the solid. The solution 
may be stored for repeated use. 
 
Disassemble the carbon dioxide electrode. If the electrode is dry, soak the glass tip of the inner 
body in Eutech Carbon Dioxide Electrode Filling Solution, Code No. EC-ISA-CO1 for two hours. 
 
Rinse the electrode thoroughly with distilled water. Put 100 ml of pH 7 buffer (0.1M NaCl added) 
in a 150 ml beaker. Place the beaker on the magnetic stirrer, and begin stirring. Immerse the tip of 
the inner body in the solution so that the reference element is covered. Make sure that the meter is 
in the mV mode.  Record the meter reading when stable. 
 
Rinse the inner body thoroughly in distilled water. Put 100 ml of pH 4 buffer (0.1M NaCl added) in 
a 150 ml beaker, place the beaker on the magnetic stirrer, and begin stirring. Immerse the tip of the 
inner body in the solution so that the reference element is covered. Observe the change in the meter 
reading carefully. In less than 30 seconds after immersion, the reading should change 100 mV. The 
meter reading should stabilize in 3-4 minutes, with a difference greater than 150 mV if the inner 
body sensing elements are operating properly.