Thermo Fisher Scientific Ion Selective Electrodes Copper User Manual

EUTECH INSTRUMENTS PTE LTD.

INSTRUCTION MANUAL

CUPRIC (COPPER) ION ELECTRODE

Instruction Manual Copper Electrode

TABLE OF CONTENTS

GENERAL INSTRUCTIONS....................................................................................................................................4

INTRODUCTION ..........................................................................................................................................................4

REQUIRED EQUIPMENT ..............................................................................................................................................4

REQUIRED SOLUTIONS...............................................................................................................................................4

GENERAL PREPARATION ..................................................................................................................................... 5

ELECTRODE PREPARATION ........................................................................................................................................5

ELECTRODE SLOPE CHECK (WITH STANDARD PH/MV METER)...................................................................................5

ELECTRODE SLOPE CHECK (WITH ION METER)...........................................................................................................6

MEASUREMENT .......................................................................................................................................................7

MEASURING HINTS ....................................................................................................................................................7

SAMPLE REQUIREMENTS............................................................................................................................................7

UNITS OF MEASUREMENT ..........................................................................................................................................7

MEASUREMENT PROCEDURES...........................................................................................................................8

DIRECT MEASUREMENT.............................................................................................................................................8

DIRECT MEASUREMENT OF CUPRIC ION (USING A STANDARD PH/MV METER)...........................................................8

DIRECT MEASUREMENT OF CUPRIC ION (USING AN ION METER) ..............................................................................10

LOW LEVEL CUPRIC DETERMINATION (USING A STANDARD PH/MV METER) ...........................................................11

LOW LEVEL CUPRIC DETERMINATION (USING AN ION METER).................................................................................12

TITRATION..............................................................................................................................................................13

TITRATION OF CUPRIC ION.......................................................................................................................................13

ELECTRODE CHARACTERISTICS.....................................................................................................................14

REPRODUCIBILITY ...................................................................................................................................................14

INTERFERENCES.......................................................................................................................................................15

PRECIPITATION AND COMPLEXATION ......................................................................................................................15

TEMPERATURE INFLUENCES ....................................................................................................................................16

ELECTRODE RESPONSE ............................................................................................................................................16

LIMITS OF DETECTION .............................................................................................................................................18

PH EFFECTS .............................................................................................................................................................18

ELECTRODE LIFE .....................................................................................................................................................19

ELECTRODE STORAGE .............................................................................................................................................19

ELECTRODE THEORY..........................................................................................................................................19

ELECTRODE OPERATION ..........................................................................................................................................19

TROUBLESHOOTING GUIDE..............................................................................................................................21

METER.....................................................................................................................................................................21

GLASSWARE ............................................................................................................................................................21

ELECTRODES ...........................................................................................................................................................21

REAGENTS ...............................................................................................................................................................22

SAMPLE ...................................................................................................................................................................22

TECHNIQUE..............................................................................................................................................................23

TROUBLESHOOTING HINTS...............................................................................................................................23

SPECIFICATIONS ...................................................................................................................................................25

EUTECH INSTRUMENTS PTE LTD.

Instruction Manual Copper Electrode

CUPRIC (COPPER) ION ELECTRODE

INSTRUCTION MANUAL

GENERAL INSTRUCTIONS

Introduction

The Cupric Ion Electrodes are used to quickly, simply, accurately, and economically measure cupric ion in aqueous solutions.

Required Equipment

1. A pH/mV meter or an ion meter, either line operated or portable.

2. Semi-logarithmic 4-cycle graph paper for calibration curves when using the meter in the mV mode.

3. A magnetic stirrer.

4. The Cupric Ion Electrode (reference electrode necessary), the Cupric Ion Combination Glass Electrode, or the Cupric Ion Combination Epoxy Electrode.

5. The Double Junction Reference with Filling Solution in the inner junction and with Filling Solution in the outer junction.

6. Polishing Paper to polish dirty or etched electrode membranes.

Required Solutions

1. Deionized or distilled water for solution and standard preparation.

2. Ionic Strength Adjuster (ISA), 5M NaNO3. To prepare this solution from your own laboratory stock, add 425 grams reagent-grade sodium nitrate, NaNO3, to a 1 liter volumetric flask about half full of distilled water. Swirl the flask to dissolve the solid. Dilute to the mark with distilled water, cap the flask, and upend it several times to thoroughly mix the solution. To each 100 ml of standard or sample, add 2 ml of ISA. The background ionic strength of the resulting solution will be 0.1M.

3. Cupric Nitrate Standard Solution, 0.1M. This solution

Instruction Manual Copper Electrode

may be prepared by adding 24.16 grams of reagent-grade Cu(NO3)2 ∃ 3H2O to a 1 liter volumetric flask about

half full of distilled water. Swirl the flask to dissolve the solid. Fill flask to the mark with distilled water, cap the flask, and upend it several times to mix the solution thoroughly.

4. Cupric Nitrate Standard Solution, 1000 ppm Cu+2. This solution may be prepared by adding 3.80 grams of

reagent-grade Cu(NO3)2 ∃ 3H2O to a 1 liter volumetric flask about half full of distilled water. Swirl the flask to dissolve the solid. Fill the flask to the mark with distilled water, cap the flask, and upend it several times to mix the solution thoroughly.

5. EDTA Titrant (1M) for Cupric Titrations. To prepare this solution from your own laboratory stock, add 37.2

grams of reagent-grade Na2EDTA ∃ 2H2O to a 100 ml volumetric flask about three-fourths full of distilled water. Swirl the flask to dissolve the solid. Add distilled water to the mark, cap the flask, and upend it several times to thoroughly mix the solution.

GENERAL PREPARATION

Electrode Preparation

Remove the rubber cap(s) covering the electrode tip(s) and the rubber insert covering the filling hole of the cupric combination ion 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 electrode(s) to the proper terminal(s) as recommended by the meter manufacturer.

Electrode Slope Check (with standard pH/mV meter)

(check electrodes each day)

1. To a 150 ml beaker, add 100 ml of distilled water and 2 ml of ISA. Place the beaker on the magnetic stirrer and begin stirring at a constant rate. After assuring that the meter is in the mV mode, lower the electrode tip(s) into the solution.

2. Using a pipette, add 1 ml of either the 0.1M or 1000 ppm cupric standard to the beaker. When the reading is stable, record the millivolt reading.

Instruction Manual Copper Electrode

3. Using a pipette, add 10 ml of the standard used above to the beaker. When the reading is stable, record the millivolt reading.

4. Determine the difference between the two readings. A difference of 27∀2 mV indicates correct electrode

operation, assuming the temperature is between 20o and 25oC. See the TROUBLESHOOTING GUIDE and TROUBLESHOOTING HINTS sections if the potential change is not within this range.

Slope is defined as the change in potential observed when the concentration changes by a factor of 10.

Electrode Slope Check (with ion meter)

(check electrodes each day)

1. Prepare standard cupric solutions whose concentrations vary be tenfold. Use either the 0.1M or 1000 ppm stock solutions and the serial dilution method for this preparation.

2. To a 150 ml beaker, add 100 ml of the lower value standard and 2 ml of ISA. Place the beaker on a magnetic stirrer and begin stirring at a constant rate. After assuring that the meter is in the concentration mode, lower the electrode tip(s) into the solution.

3. After the reading has stabilized, 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 electrode(s) with distilled water and blot dry.

5. To a 150 ml beaker, add 100 ml of the higher value standard and 2 ml of ISA. Place the beaker on the magnetic stirrer and begin stirring at a constant rate. Lower the electrode tip(s) into the solution.

6. After the reading has stabilized, 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%. If the slope is not within this range, see the TROUBLESHOOTING GUIDE and TROUBLESHOOTING HINTS sections.

Instruction Manual Copper Electrode

MEASUREMENT

Measuring Hints

All samples and standards should be at the same temperature for precise measurement.

Constant, but not violent, stirring is necessary for accurate measurements. Magnetic stirrers can generate sufficient heat to change the solution temperature. To counteract this effect, place a piece of insulating material, such as styrofoam sheet, between the stirrer and beaker.

Always rinse the electrode(s) with distilled water and blot dry between measurements. Use a clean, dry tissue to prevent crosscontamination.

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.

Sample Requirements

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 before using these electrodes in other organic solvents.

The temperature of the standard and of the sample solution should be the same and below 80 degrees C. About a 4% error in the slope will occur for each 1oC difference in temperature.

Interferences should be absent. If they are present, use the procedure found in the Interference and Electrode Response sections to remove them.

Adjust sample pH with 1M HNO

to below pH 7 to avoid

precipitation of cupric hydroxide, Cu(OH)2.

Units of Measurement

Cupric ion concentrations are measured in units of parts per million, moles per liter, equivalents per liter, or any other

Instruction Manual Copper Electrode

convenient concentration unit. Table 1 indicates some of these concentration units.

TABLE 1: Concentration Unit Conversion Factors

ppm Cu+2 moles/liter

6354.0 1.0X10-1

635.0 1.0X10-2

63.5 1.0X10-3

6.4 1.0X10-4

MEASUREMENT PROCEDURES

Direct Measurement

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.

Direct Measurement of Cupric Ion (using a standard pH/mV meter)

1. By serial dilution of the 0.1M or 1000 ppm standards, prepare 10-2, 10-3, and 10-4M or 100 and 10 ppm standards for the cupric ion. To 100 ml of each standard, add 2 ml of ISA. 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 10-4M or 10 ppm standard in a 150 ml beaker, place the beaker on the magnetic stirrer and begin stirring at a constant rate.

3. Lower the electrode tip(s) into the solution. Make sure that the meter is in the mV mode. When the reading has stabilized, record the mV reading.

4. Place 100 ml of the 10

-3

M or 100 ppm standard in a 150 ml beaker, place the beaker on the magnetic stirrer and begin stirring at a constant rate.

5. After rinsing the electrode(s) with distilled water and blotting dry, immerse the electrode tip(s) in the solution. When the reading has stabilized, record the mV reading.

Instruction Manual Copper Electrode

6. Place 100 ml of the 10-2M or 1000 ppm standard in a 150 ml beaker, place the beaker on the magnetic stirrer and begin stirring at a constant rate.

7. After rinsing the electrode(s) with distilled water and blotting dry, immerse the electrode tip(s) in the solution. When the reading has stabilized, record the mV reading.

8. Using the semi-logarithmic graph paper, plot the mV reading (linear axis) against concentration (log axis). A typical calibration curve can be found in Figure 1.

A calibration curve is constructed on semilogarithmic paper when using a pH/mV meter in the millivolt mode. The measured electrode potential in mV (linear axis) is plotted against the standard concentration (log axis). In the linear region of the curve, only three standards are necessary to determine a calibration curve. In the non-linear region, additional points must be measured. The direct measurement procedures given are for the linear portion of the curve. The non-linear portion of the curve requires the use of low level procedures.

9. To a clean, dry 150 ml beaker, add 100 ml of the sample and 2 ml of ISA. Place the beaker on the magnetic stirrer and begin stirring at a constant rate.

10. After rinsing the electrode tip(s) in distilled water

+ 19 hidden pages