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Cyanide Electrode 

 

Instruction Manual

 

 

2

TABLE OF CONTENTS

 

 

GENERAL INSTRUCTIONS .......................................................................................................... 3 

Introduction ..............................................................................................................................................3 
Required Equipment.................................................................................................................................3 
Required Solutions ...................................................................................................................................3 

GENERAL PREPARATION............................................................................................................ 4 

Electrode Preparation ...............................................................................................................................4 
Electrode Slope Check (with pH/mV meter) ...........................................................................................4 
Electrode Slope Check (with an ion meter)..............................................................................................4 

MEASUREMENT.............................................................................................................................. 5 

Measuring Hints .......................................................................................................................................5 
Sample Requirements...............................................................................................................................5 
Units of Measurement ..............................................................................................................................6 

MEASUREMENT PROCEDURE ................................................................................................... 6 

Direct Measurement .................................................................................................................................6 
Direct Measurement of Cyanide (using a pH/mV meter) ........................................................................6 
Direct Measurement of Cyanide (using an ion meter) .............................................................................7 
Low-Level Cyanide Measurements (using a pH/mV meter)....................................................................8 

ELECTRODE CHARACTERISTICS............................................................................................. 9 

Reproducibility.........................................................................................................................................9 
Interferences .............................................................................................................................................9 
Complexation .........................................................................................................................................10 
Temperature Influences..........................................................................................................................10 
Electrode Response ................................................................................................................................11 
Limits of Detection.................................................................................................................................12 
pH Effects...............................................................................................................................................12 
Electrode Life.........................................................................................................................................12 
Electrode Storage ...................................................................................................................................12 

ELECTRODE THEORY ................................................................................................................ 12 

Electrode Operation ...............................................................................................................................13 

TROUBLESHOOTING GUIDE .................................................................................................... 14 

Meter ......................................................................................................................................................14 
Plastic-ware ............................................................................................................................................14 
Electrodes ...............................................................................................................................................14 
Standards and Reagents..........................................................................................................................15 
Sample....................................................................................................................................................15 
Technique...............................................................................................................................................15 

TROUBLESHOOTING HINTS..................................................................................................... 16 

SPECIFICATIONS.......................................................................................................................... 18 

ORDERING INFORMATION....................................................................................................... 18 

Summary of Contents for CYANIDE EPOXY

Page 1: ...Instruction Manual Cyanide Electrode 1 EUTECH INSTRUMENTS PTE LTD INSTRUCTION MANUAL CYANIDE ION ELECTRODE ...

Page 2: ...nt 6 Direct Measurement of Cyanide using a pH mV meter 6 Direct Measurement of Cyanide using an ion meter 7 Low Level Cyanide Measurements using a pH mV meter 8 ELECTRODE CHARACTERISTICS 9 Reproducibility 9 Interferences 9 Complexation 10 Temperature Influences 10 Electrode Response 11 Limits of Detection 12 pH Effects 12 Electrode Life 12 Electrode Storage 12 ELECTRODE THEORY 12 Electrode Operati...

Page 3: ...n meter either line operated or portable 2 Semi logarithmic 4 cycle graph paper for preparing calibration curves when using the meter in the mV mode 3 A magnetic stirrer 4 Eutech Cyanide Ion Combination Epoxy body Electrode Code no EC CN 03 5 Lab ware made of plastic not glass 6 Polishing Paper Code no EC MIS PP to polish dirty or etched electrode membranes Required Solutions 1 Deionized or distil...

Page 4: ...on electrode or the reference electrode Fill the reference electrode or the combination electrode with the filling solution shipped with the electrode to a level just below the fill hole No preparation is required with a sealed reference electrode Connect the electrodes to the proper terminals as recommended by the meter manufacturer Electrode Slope Check with pH mV meter Check electrodes each day...

Page 5: ...ufacturer s instructions Correct electrode operation is indicated by a slope of 93 100 See TROUBLESHOOTING section if the slope is not within this range MEASUREMENT Measuring Hints All samples and standards should be at the same temperature for precise measurement A difference of 1o C in temperature will result in about a 2 measurement error Constant but not violent stirring is necessary for accur...

Page 6: ...e above 10 so that cyanide is present as CN 1 rather than as HCN in all standards and samples Units of Measurement 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...

Page 7: ... Using the calibration curve determine the sample concentration 7 The calibration should be checked every 2 hours Assuming no change in ambient temperature place the electrode tips in the mid range standard After the reading has stabilized compare it to the original reading recorded in Step 3 above A reading differing by more than 0 5 mV or a change in the ambient temperature will necessitate the ...

Page 8: ...ide measurement procedure in the non linear portion of the calibration curve below 8X10 6 M or 0 2 ppm A more accurate electrode indicator technique such as titration using a silver sulfide ion electrode may be preferred below these levels 1 By serial dilution prepare 100 ml of 1 0X10 3 M or 10 ppm cyanide standard from the 1 0X10 2 M or 1 000 ppm cyanide standard 2 Using a 150 ml plastic beaker a...

Page 9: ...s photographic developer Ions forming very insoluble silver salts will cause the electrodes to malfunction if present in solution at sufficiently high levels to form a layer of silver salt on the membrane surface Electrode performance can be restored by polishing if the surface of the sensing element becomes contaminated See section Electrode Response for proper polishing procedure Solutions conta...

Page 10: ...e solution s pH 4 Add EDTA disodium to about 0 02M or about 0 76 grams Na2 EDTA per 100 ml sample In a hood heat the mixture to about 50o C for about five minutes to speed up the decomplexation After cooling the solution add 10M NaOH ISA until the pH 13 The cyanide remains free long enough for concentration measurements to be made since EDTA complexes of the metals break up very slowly This method...

Page 11: ...n electrode slope may mean that the electrode membrane needs polishing To polish the membrane 1 If using polishing paper cut off a 1 2 piece and place it face up on the lab bench 2 Put a few drops of distilled or deionized water in the center of the paper 3 Holding the paper cotton steady with one hand bring the membrane of the electrode down perpendicular to the paper and with a slight swirling m...

Page 12: ...st results pH Effects A cyanide electrode can be used over the pH range 11 to 13 It is necessary to adjust the sample pH to above 11 using the recommended ISA to convert all cyanic acid species in solution to cyanide Electrode Life A cyanide ion electrode will last six months in normal laboratory use On line measurements might shorten operational lifetime to several months In time the response tim...

Page 13: ... or complexed cyanide ions The activity is related to the free ion concentration Cf by the activity coefficient γ by X γ Cf Activity coefficients vary depending on total ionic strength I defined as I Σ CxZx 2 where Cx concentration of ion X Zx charge of ion X Σ sum of all of the types of ions in the solution In the case of high and constant ionic strength relative to the sensed ion concentration t...

Page 14: ...good measurement Be sure to wash the plastic ware well with a mild detergent and rinse very well with distilled or deionized water Electrodes The electrodes may be checked by using the procedure found in the sections entitled Electrode Slope Check 1 Be sure to use distilled or deionized water when following the procedures given in Electrode Slope Check 2 If the electrode fails to respond as expect...

Page 15: ...lexing agents or substances which could affect the response or physically damage the sensing electrode or the reference electrode if the electrodes work perfectly in the standard but not in the sample Try to determine the composition of the samples prior to testing to eliminate a problem before it starts See Measuring Hints Sample Requirements and Interferences Technique Be sure that the electrode...

Page 16: ...lution Noisy or Unstable defective meter check meter with shorting Readings readings strap continuously or rapidly changing air bubble on membrane remove bubble by re dipping electrode electrode exposed soak electrode in to interferences cyanide standard ISA not used use recommended ISA meter or stirrer not ground meter or stirrer grounded defective electrode replace electrode Drift reading sample...

Page 17: ...move bubble by re dipping probe Incorrect Answer incorrect scaling of plot millivolts on the linear but calibration semi log paper axis On the log axis be sure curve is good concentration numbers within each decade are increasing easing concentration incorrect sign be sure to note sign of millivolt number correctly incorrect standards prepare fresh standards wrong units used apply correct conversi...

Page 18: ...o 80o C Resistance 1 Mohms Reproducibility 2 Size 110 mm length 12 mm diameter 1 m cable length Storage store in cyanide standard with ISA added ORDERING INFORMATION CODE NO DESCRIPTION EC CN 03 Cyanide Ion Electrode epoxy body combination EC ISA CN1 BT Ionic Strength Adjuster ISA 10M NaOH EC MIS PP Polishing Paper for the Cyanide Ion Electrodes ...

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