eutech-instruments cyanide epoxy User Manual

Cyanide Electrode 

 

Instruction Manual

 

 

6

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 epoxy body electrode. Please check with Eutech Instruments Pte Ltd. before using the 
electrode in other solvents. 
 
The temperature of the sample solutions and of the standard solutions should be the same and below 
80

o

C.  

 
Interferences should be absent. If they are present, use the procedure found in the 

 

and 

 sections to remove them. 

Measurements above 1X10

-3

M should be done infrequently, as cyanide ion slowly erodes the 

membrane. (See section 

.) It may be necessary to polish the membrane occasionally 

with polishing paper or jeweller's rouge as the electrode is used. Samples should be diluted below 
1X10

-3

M if possible. 

 
Proper pH is ensured if ISA is used. The pH should be above 10 so that cyanide is present as CN

-1

 

rather than as HCN in all standards and samples. 
 

 
Cyanide ions can be measured in units of ppm, moles per liter, or any other convenient 
concentration unit.  Table 1 indicates some concentration units and conversion factors. 
 
 TABLE 

1: Concentration Unit Conversion Factors         

 
                 ppm CN-             moles/liter 
                 26.00         

1.0X10

-3

 

                 10.00         

3.8X10

-4 

                  2.60       

 

1.0X10

-4

 

                  1.00       

 

3.8X10

-5 

                  0.26       

 

1.0X10

-5 

 
 
MEASUREMENT PROCEDURE 
 

 
Direct measurement is a simple procedure for measuring a large number of samples. A single meter 
reading is all that is required for each sample. The ionic strength of samples and standards should 
be made the same by adjustment with ISA. The temperature of both sample solutions and standard 
solutions should be the same. 
 

 

1. 

By serial dilution, prepare 10

-3

, 10

-4

, and 10

-5

M or 10, 1 and 0.1 ppm standards for the 

cyanide ion from the 0.01M or 1,000 ppm standards. Prepare standards with a composition 
similar to the samples if the samples have an ionic strength above 0.1M. 

2. 

Place 100 ml of the most dilute standard solution in a 150 ml plastic beaker. Place the 
beaker on the magnetic stirrer and begin stirring at a constant rate. Add 1 ml of 10M