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LEAD EPOXY
User Manual
23 pgs343.24 Kb0

Eutech Instruments LEAD EPOXY User Manual

EUTECH INSTRUMENTS PTE LTD.
INSTRUCTION MANUAL
LEAD ION ELECTRODE
TABLE OF CONTENTS
GENERAL INSTRUCTIONS ..........................................................................................................1
GENERAL PREPARATION............................................................................................................3
MEASUREMENT..............................................................................................................................4
MEASUREMENT PROCEDURE ...................................................................................................5
ELECTRODE CHARACTERISTICS...........................................................................................13
ELECTRODE THEORY................................................................................................................15
TROUBLESHOOTING GUIDE....................................................................................................17
TROUBLESHOOTING HINTS.....................................................................................................19
SPECIFICATIONS..........................................................................................................................21
ORDERING INFORMATION.......................................................................................................21
Instruction Manual Lead Electrode
GENERAL INSTRUCTIONS ............................................................Error! Bookmark not defined.
Introduction............................................................................................................Error! Bookmark not defined.
Required Equipment...............................................................................................Error! Bookmark not defined.
Required Solutions.................................................................................................Error! Bookmark not defined.
GENERAL PREPARATION.........................................................ERROR! BOOKMARK NOT DEFINED.
Electrode Preparation...................................................................................... ERROR! BOOKMARK NOT DEFINED.
Electrode Slope Check (with pH/mV meter)................................................... E
Electrode Slope Check (with ion meter) ......................................................... E
RROR! BOOKMARK NOT DEFINED. RROR! BOOKMARK NOT DEFINED.
MEASUREMENT..............................................................................................Error! Bookmark not defined.
Measuring Hints.............................................................................................. ERROR! BOOKMARK NOT DEFINED.
Sample Requirements...................................................................................... E
Units of Measurement..................................................................................... E
RROR! BOOKMARK NOT DEFINED. RROR! BOOKMARK NOT DEFINED.
MEASUREMENT PROCEDURE ..................................................... Error! Bookmark not defined.
Direct Measurement........................................................................................ ERROR! BOOKMARK NOT DEFINED.
Direct Measurement of Silver (using a pH/mV meter) ................................... E
Direct Measurement of Silver (using an ion meter)........................................ E
Direct Measurement of Sulfide (using a pH/mV meter) ................................. E
Direct Measurement of Sulfide (using an ion meter)...................................... E
Low Level Silver Determinations (using a pH/mV meter) ............................. E
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TITRATION.........................................................................................Error! Bookmark not defined.
Titration of Sulfide.......................................................................................... ERROR! BOOKMARK NOT DEFINED.
Titration of Silver............................................................................................ E
Low Level Chloride Titration.......................................................................... E
Indicator Titration ........................................................................................... E
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ELECTRODE CHARACTERISTICS...............................................Error! Bookmark not defined.
Reproducibility ................................................................................................ ERROR! BOOKMARK NOT DEFINED.
Interference...................................................................................................... E
Complexation.................................................................................................. E
Temperature Influences................................................................................... E
Electrode Response ......................................................................................... E
Limits of Detection.......................................................................................... E
pH Effects........................................................................................................ E
Electrode Life.................................................................................................. E
Electrode Storage ............................................................................................ E
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ELECTRODE THEORY....................................................................Error! Bookmark not defined.
Electrode Operation......................................................................................... ERROR! BOOKMARK NOT DEFINED.
TROUBLESHOOTING GUIDE........................................................ Error! Bookmark not defined.
Meter ............................................................................................................... ERROR! BOOKMARK NOT DEFINED.
Glassware........................................................................................................ E
Electrodes........................................................................................................ E
Standards and Reagents................................................................................... E
Sample............................................................................................................. E
Technique........................................................................................................ E
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TROUBLESHOOTING HINTS......................................ERROR! BOOKMARK NOT DEFINED.
SPECIFICATIONS.............................................................................. Error! Bookmark not defined.
ORDERING INFORMATION........................................ERROR! BOOKMARK NOT DEFINED.
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EUTECH INSTRUMENTS PTE LTD.
LEAD ION ELECTRODE
INSTRUCTION MANUAL
GENERAL INSTRUCTIONS
Introduction
Eutech Instruments Lead Ion Electrode is used to measure lead or sulfate 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. Linear graph paper is recommended for low level measurements or lead/sulfate titration.
3. A magnetic stirrer.
4. Eutech Lead Ion Combination Epoxy-body Electrode, Code no. EC-PB-03.
6. Lab-ware made of plastic, not glass, for all low level measurements.
7. Polishing Paper, Code no. EC-MIS-PP, to polish dirty or etched electrode membranes.
Required Solutions
1. Deionized or distilled water for solution and standard preparation.
2. Methanol-formaldehyde solution. To prepare this solution from your own laboratory stock, add 3 drops of 37% formaldehyde to 1,000 ml of reagent-grade methanol. This solution is used to decrease the solubility and retard oxidation of the membrane.
3. Eutech Ionic Strength Adjuster (ISA), 5M NaClO4, Code No. EC-ISA-PB1-BT. To prepare this solution from your own laboratory stock, half fill a one liter volumetric flask with distilled water and add 700 grams of reagent-grade NaClO4·H2O. 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. 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.
4. Eutech Lead Perchlorate Standard, 0.1M Pb(ClO4)2, Code no. EC-SCS-PB1-BT. To prepare this solution from your own laboratory stock, half fill a one liter volumetric flask with distilled water and add 46.01 grams of reagent-grade lead perchlorate,
Instruction Manual Lead Electrode
Pb(ClO4)2·3H2O. Swirl the flask gently to dissolve the solid. Fill the flask to the mark with distilled water, cap, and upend several times to thoroughly mix the solution.
5. Eutech Lead Perchlorate Standard, 1,000 ppm Pb(ClO4)2, Code no. EC-SCS-PB2-BT. To prepare this solution from your own laboratory stock, half fill a one liter volumetric flask with distilled water and add 2.30 grams of reagent-grade lead perchlorate, Pb(ClO4)2·3H2O. Swirl the flask to dissolve the solid. Fill the flask to the mark with distilled water, cap, and upend several times to thoroughly 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 lead 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 electrodes to the proper terminals as recommended by the meter manufacturer.
Electrode Slope Check (with pH/mV meter)
(Check electrodes each day)
1. To a 150 ml beaker, add 50 ml of methanol-formaldehyde solution and 50 ml of distilled water. Add 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 lead standard to the beaker. When the reading has stabilized, record the mV reading.
3. Using a pipet, add 10 ml the same lead standard used above to the beaker. When the reading has stabilized, record the mV reading.
4. Determine the difference between the two readings. The electrode is operating correctly if
o
the millivolt potential has changed by 25±2, assuming the temperature is between 20
o
25
C. See the TROUBLESHOOTING sections if the potential change is not within this range.
and
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 lead solutions whose concentrations vary by tenfold. Use either the 0.1M or 1,000 ppm lead standard. Use the serial dilution method for this preparation.
2. To a 150 ml beaker, add 50 ml of methanol-formaldehyde solution and 50 ml of the lower value standard. Add 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. Assure that the meter is in the concentration mode.
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3. 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 electrodes with distilled water and blot dry.
5. To another 150 ml beaker, add 50 ml of methanol-formaldehyde solution and 50 ml of the higher value standard. Add 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 sections 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 1oC in temperature will result in a 4% measurement error.
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 insulation material, such as styrofoam sheet, between the stirrer and beaker.
Use plastic lab-ware for all low level measurements in order to minimize absorption on container walls. Always rinse the electrodes with distilled water and blot dry between measurements. Use a clean, dry tissue to prevent cross-contamination.
To prevent oxidation of the membrane, always use methanol-formaldehyde solution to mix with all standards and samples.
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 Eutech Instruments Pte Ltd. before using these electrodes in other organic solvents.
Instruction Manual Lead Electrode
The temperature of the standard solutions and of the sample solutions should be the same and below 80oC. 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 Interferences and Electrode Response sections to remove them.
Units of Measurement
Lead concentrations are measured in units of ppm as lead, 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 Pb+2 M ppm SO
-4
20.7 1.0X10
207.0 1.0X10
9.6
-3
96.0
-2
4
2070.0 1.0X10-2 960.0
MEASUREMENT PROCEDURE
Direct Measurement
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 solution and standard solution should be the same.
Direct Measurement of Lead (using a pH/mV meter)
1. By serial dilution, prepare 10-2M, 10-3M, and 10-4M or 100 ppm and 10 ppm standards, from the 0.1M 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 50 ml of the 10-4M or 10 ppm standard in a 150 ml beaker and add 50 ml of methanol-formaldehyde solution. Place the beaker on the magnetic stirrer and begin stirring at a constant rate. Add 2 ml of ISA. After assuring that the meter is in the mV mode, lower the electrode tips into the solution. When the reading has stabilized, record the mV reading.
3. Place 50 ml of the 10-3M or 100 ppm standard in a 150 ml beaker and add 50 ml of methanol-formaldehyde solution. Place the beaker on the magnetic stirrer and begin stirring. Add 2 ml of ISA. After rinsing the electrodes with distilled water, blot dry, and immerse the electrode tips in the solution. When the reading has stabilized, record the mV reading.
4. Place 50 ml of the 10-2M or 1,000 ppm standard in a 150 ml beaker and add 50 ml of methanol-formaldehyde solution. Place the beaker on the magnetic stirrer and begin stirring. Add 2 ml of ISA. After rinsing the electrodes with distilled water, blot dry, and immerse the electrode tips in the solution. When the reading has stabilized, record the mV reading.
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