EUTECH INSTRUMENTS EC-NA02, EC-SCS-LNA1-BT, EC-SCS-LNA2-BT, EC-SCS-LNA3-BT, EC-ISA-LNA1-BT Instruction Manual

Instruction Manual Sodium Electrode

EUTECH INSTRUMENTS PTE LTD.

INSTRUCTION MANUAL

SODIUM ION ELECTRODE

Sodium Electrode Instruction Manual

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TABLE OF CONTENTS

GENERAL INSTRUCTIONS ..........................................................................................................1

REQUIRED EQUIPMENT..................................................................................................................................1

REQUIRED SOLUTIONS ..................................................................................................................................1

GENERAL PREPARATION............................................................................................................2

ELECTRODE PREPARATION............................................................................................................................2

ELECTRODE SLOPE CHECK (WITH PH/MV METER) .......................................................................................2

ELECTRODE SLOPE CHECK (WITH ION METER) .............................................................................................2

MEASUREMENT..............................................................................................................................3

MEASURING HINTS........................................................................................................................................3

SAMPLE REQUIREMENTS...............................................................................................................................3

UNITS OF MEASUREMENT .............................................................................................................................3

MEASUREMENT PROCEDURE ................................................................................................... 4

DIRECT MEASUREMENT ................................................................................................................................4

DIRECT MEASUREMENT OF SODIUM (USING A PH/MV METER) ....................................................................4

DIRECT MEASUREMENT OF SODIUM (USING AN ION METER)........................................................................5

LOW LEVEL SODIUM DETERMINATION (USING A PH/MV METER)................................................................6

LOW LEVEL SODIUM DETERMINATION (USING AN ION METER) ...................................................................7

ELECTRODE CHARACTERISTICS............................................................................................. 7

REPRODUCIBILITY .........................................................................................................................................7

INTERFERENCE ..............................................................................................................................................7

TEMPERATURE INFLUENCES..........................................................................................................................8

ELECTRODE RESPONSE..................................................................................................................................8

LIMITS OF DETECTION...................................................................................................................................9

PH EFFECTS ...................................................................................................................................................9

ELECTRODE LIFE .........................................................................................................................................10

ELECTRODE STORAGE.................................................................................................................................10

ELECTRODE THEORY................................................................................................................10

ELECTRODE OPERATION .............................................................................................................................10

TROUBLESHOOTING GUIDE....................................................................................................11

METER.........................................................................................................................................................11

GLASSWARE ................................................................................................................................................11

ELECTRODES ...............................................................................................................................................11

STANDARDS AND REAGENTS.......................................................................................................................12

SAMPLE .......................................................................................................................................................12

TECHNIQUE..................................................................................................................................................12

TROUBLESHOOTING HINTS.....................................................................................................13

SPECIFICATIONS..........................................................................................................................14

ORDERING INFORMATION.......................................................................................................14

Instruction Manual Sodium Electrode

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EUTECH INSTRUMENTS PTE LTD.

SODIUM ION ELECTRODE

INSTRUCTION MANUAL

GENERAL INSTRUCTIONS

Eutech Instruments Sodium Ion Electrode is used to measure sodium ions in aqueous solutions
quickly, simply, accurately, and economically.

Required Equipment

1. A pH/mV meter or an ion 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 Sodium Ion Combination Epoxy-body Electrode, Code no. EC-LNA-03.

5. Lab-ware made of glass, except for low level measurements where plastic-ware is

required.

Required Solutions

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

2. Eutech Ionic Strength Adjuster (ISA), 4M NH4Cl/4M NH4OH, Code no. EC-ISA-LNA1-

BT. To prepare this solution from your own laboratory stock, half fill a 1,000 ml
volumetric flask with distilled water and add 214 grams of reagent-grade ammonium
chloride (NH4Cl). Under a hood, add 270 ml of concentrated ammonium hydroxide
(NH

4

OH), swirl the flask gently to dissolve the solid, and allow to cool. Fill the flask to

the mark with distilled water, cap, and upend several times to mix the solution.

3. Dilute Electrode Rinse Solution. To prepare this solution from your own laboratory

stock, add 20 ml of ISA to a one liter volumetric flask and fill to the mark with distilled
water. Use this solution to rinse the electrode between measurements. DO NOT RINSE
WITH DISTILLED WATER.

4. Eutech Sodium Standard, 0.1M NaCl, Code no. EC-SCS-LNA1-BT. To prepare this

solution from your own laboratory stock, half fill a one liter volumetric flask with
distilled water and add 5.84 grams of reagent-grade NaCl. Swirl the flask gently to
dissolve the solid. Fill the flask to the mark with distilled water, cap, and upend several
times to mix the solution.

5. Eutech Sodium Standard, 1,000 ppm Na

+

, Code no. EC-SCS-LNA2-BT. To prepare this
solution from your own laboratory stock, half fill a one liter volumetric flask with
distilled water and add 2.542 grams of reagent grade NaCl. Swirl the flask gently to
dissolve the solid. Fill the flask to the mark with distilled water, cap, and upend several
times to mix the solution.

Sodium Electrode Instruction Manual

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6. Eutech Sodium Standard, 100 ppm Na+, Code no. EC-SCS-LNA3-BT. To prepare this

solution from your own laboratory stock, half fill a one liter volumetric flask with
distilled water and add 0.254 grams of reagent grade NaCl. Swirl the flask to dissolve the
solid. Fill the flask to the mark with distilled water, cap, and upend several times to mix
the solution.

GENERAL PREPARATION

Electrode Preparation

Remove the rubber caps covering the electrode tips and the rubber insert covering the filling hole of
the reference electrode. Fill the combination electrode or the reference 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 of the meter as
recommended by the meter manufacturer. Soak the sodium electrode tip overnight in the electrode
storage solution.

Electrode Slope Check (with pH/mV meter)

(Check electrodes each day)

1. To a 150 ml glass beaker, add 100 ml of distilled water 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 millivolt mode, lower the electrode tips into the solution.

2. Using a pipet, add 1 ml of 0.1M or 1,000 ppm sodium standard to the beaker. When the
reading has stabilized, record the mV reading.

3. Using a pipet, add 10 ml of the same sodium standard used above to the beaker. When
the reading has stabilized, record the mV reading.

4. Determine the difference between the two readings. A difference of 56±2 mV indicates
correct electrode operation assuming the solution temperature is between 20o and 25oC.
See the

TROUBLESHOOTING section if the potential change is not within this range.

Slope is defined as the change in potential observed when the concentration changes be a factor of

10.

Electrode Slope Check (with ion meter)

(Check electrodes each day)

1. Prepare standard sodium solutions whose concentrations vary by tenfold. Use either the

0.1M NaCl or the 1,000 ppm sodium standard. Use 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 the magnetic stirrer and begin stirring at a constant rate. Lower the electrode
tips into the solution. Assure that the meter is in the concentration mode.

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

Instruction Manual Sodium Electrode

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4. Rinse the electrodes with the electrode rinse solution and blot dry.

5. To another 150 ml beaker, add 100 ml of the higher value standard and 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 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, preferably
ambient temperature. A difference of 1oC in temperature will result in about a 2% measurement
error. The electrodes should not be used above 70oC.

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 insulating material, such as a styrofoam sheet, between the stirrer and the beaker.

Always rinse the electrodes with electrode rinse solution from a wash bottle between
measurements. Use a clean, dry tissue to prevent cross contamination. Never use distilled water.

Store the electrodes in electrode storage solution between measurements. Do not store in air or
distilled water. Always soak new electrodes overnight in electrode storage solution prior to first
use. When making low level sodium measurements, use a dilute sodium chloride storage solution.
Add 1 ml of ISA to 100 ml of dilute storage solution.

Plastic lab-ware should be used for low level measurements (<1 ppm). All measurements should be
made in basic solution. All samples and standards should be adjusted to a pH > 9 with ISA.
For samples with high ionic strength, prepare standards whose composition is similar to the sample.

Always check to see that the membrane is free from air bubbles after immersion into standard or
sample.

Sample Requirements

The sample measuring range is pH 9-12. Use the ISA recommended to adjust the pH for best
accuracy. Make sure that the samples and standards are at the same temperature. The glass
electrode sensing bulb will not be attacked by most organic solvents.

Units of Measurement

Sodium concentrations are measured in units of parts per million, equivalents per liter, moles per
liter, or any other convenient concentration unit. Table 1 indicates some of the concentration unit
conversion factors.