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CONTENTS GENERAL INFORMATION Introduction Required Equipment Required Solutions USING THE ELECTRODE Set up Electrode Assembly and Preparation Checking Electrode Operation (Slope) Before Analysis Units of Measurement Sample Requirements Sample Storage Measuring Hints Analytical Procedures Analytical Techniques Direct Calibration Known Addition Electrode Storage TROUBLESHOOTING Troubleshooting Checklist...
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Flip-top Spout Internal Filling Solution, 50 mL bottle Tweezers Carbon Dioxide Electrode Membrane-Spacer Assemblies, box of four with two O-rings Figure 1 Contents Of Storage Box...
GENERAL INFORMATION Introduction The Orion 95-02 Carbon Dioxide Electrode allows fast simple, economical, and accurate measurements of carbon dioxide, carbonate, and bicarbonate aqueous solutions. General analytical procedures, required solutions, electrode characteristics, and electrode theory are discussed in this manual. Operator instructions for Orion Meters are outlined in the individual meter’s...
Required Solutions Distilled or Deionized Water - To prepare all solutions and standards Standard Solutions Orion No. Standard Solutions - 0.1 M Sodium Bicarbonate 950206 Standard Solution 1000 ppm as CaCO Standard Solution 950207 1000 ppm as CO Standard Solution - To Customer prepare, dilute 22.7 mL of 0.1 M standard, prepared...
USING THE ELECTRODE Set-Up Electrode Assembly And Preparation The electrode is shipped assembled, with a membrane in place for packing. Disassemble the electrode as shown in step 1 of Figure 2, and discard the membrane. Reassemble according to instructions in Figure 2.
Checking Electrode Operation (Slope) These are general instructions which can be used with most meters to check electrode operation. See individual meter instruction manuals for more specific information. This procedure measures electrode slope. Slope is defined as the change in millivolts observed with every tenfold change in concentration.
Before Analysis Units of Measurement Carbon dioxide can be measured in units of moles per liter, parts per million as carbon dioxide, parts per million as calcium carbonate, or any other convenient concentration unit. See Table 1 for conversion units. Table 1 Concentration Unit Conversion Factors Moles/Liter...
Sample Storage If possible, samples should be measured at once, waiting only a sufficient time for the sample to come to the temperature of the electrode. In an open 150 mL beaker at 25° C, carbon dioxide diffuses out of an acidic solution at a rate of about 3% per minute with stirring and 0.5% without stirring.
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- Always rinse electrodes with distilled water between measurements (see Electrode Preparation). Shake after rinsing to prevent solution carry over. Blot dry. Do not wipe or rub the sensing membrane. - Allow all standards and samples to come to room temperature for precise measurement.
Analytical Procedures Analytical Techniques A variety of analytical techniques are available to the analyst. The following is a description of these techniques. Direct Calibration is a simple procedure for measuring a large number of samples. Only one meter reading is required for each sample.
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If using a meter with direct concentration readout capability See individual meter instruction manuals for more specific information. 1. Measure 50 mL of the more dilute standard into a 150 mL beaker. Add 5 mL carbon dioxide buffer. Stir thoroughly. 2.
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If using a meter with millivolt readout only 1. Adjust the meter to measure mV. 2. Measure 50 mL of the more dilute standard into a 150 mL beaker. Add 5 mL carbon dioxide buffer. Stir thoroughly. 3. Rinse electrodes with distilled water, blot dry and place into the beaker.
Known Addition Known Addition is a convenient technique for measuring samples because no calibration curve is needed. It can be used to verify the results of a direct calibration or to measure the total concentration of an ion in the presence of a large excess of a complexing agent. The sample potential is measured before and after addition of a standard solution.
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Known Addition Table for an added volume one-tenth the sample volume. Slopes (in the column headings) are units of mV/decade ∆E Concentration Ratio Monovalent (57.2) (58.2) (59.2) (60.1) 0.2894 0.2933 0.2972 0.3011 0.2806 0.2844 0.2883 0.2921 0.2722 0.2760 0.2798 0.2835 0.2642 0.2680 0.2717...
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If using an instrument with direct known addition readout capability See individual meter instruction manuals for more specific information. 1. Set up meter to measure in the known addition mode. 2. Measure 50 mL of the sample into a beaker. Rinse electrodes with distilled water, place in sample solution.
From Table 3, find the value, Q, that corresponds to the change in potential, ∆E. To determine the original sample concentration, multiply Q by the concentration of the added standard: = QC where: = standard concentration = sample concentration = reading from known addition table The table of Q values is calculated for a 10% volume change for electrodes with slopes between 57.2 to 60.1 mV/decade.
TROUBLESHOOTING Troubleshooting checklist Symptom Possible cause Off Scale or Defective meter Over-range reading Defective inner body Electrodes not plugged in properly Internal filling solution not added Air bubble on membrane Electrodes not in solution Noisy or unstable Insufficient internal filling solution readings (erratic- rapidly changing) Defective meter...
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Next Step Perform meter checkout procedure Refer to Troubleshooting Guide (check inner body operation) Unplug electrodes and reseat Fill outer body of electrode with proper amount of internal filling solution Remove bubble by redipping electrode Put electrodes in solution Fill outer body of electrode with proper amount of internal filling solution, see Electrode Preparation Perform meter checkout procedure (see meter instruction manual) Ensure that bottom cap is screwed on tight enough to close gap between...
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Symptom Possible Causes Drift (readings Defective inner body changing slowly in one direction) Electrode exposed to air for extended period Samples and standards at different temperaures Low slope or Standards contaminated or No slope incorrectly made buffer not used Standard used as CO buffer Electrode exposed to air Membrane failure (wet,...
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Next Step Check inner body operation Hold electrode by outer body and pull up on electrode cable. Internal filling solution will flow under membrane and restore electrode response Allow solutions to come to same temperature before measurement Prepare fresh standards Use recommended CO buffer, Orion No.
Troubleshooting Guide The most important principle in troubleshooting is to isolate the components of the system and check each in turn. The components of the system are: 1) Meter, 2) Electrodes, 3) Standard, 4) Sample, and 5) Technique. Meter The meter is the easiest component to eliminate as a possible cause of error.
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6. Before replacing a “faulty” electrode, review the instruction manual and be sure to: -Clean the electrode thoroughly -Prepare the electrode properly -Use proper filling solutions, CO buffer, and standards -Measure correctly -Review Troubleshooting Checklist Standard The quality of results depends greatly upon the quality of the standards.
Assistance After troubleshooting all components of your measurement system, contact The Technical Edge for Orion products. Within the United States call 1.800.225.1480, outside the United States call 978.232.6000 or fax 978.232.6031. In Europe, the Middle East and Africa, contact your local authorized dealer. For the most current contact information, visit www.thermo.com.
ELECTRODE CHARACTERISTICS Electrode Response When plotted on semilogarithmic paper, electrode potential response to carbon dioxide concentration is a straight line over two decades of concentration (5 x 10 M to 2 x 10 M) with a slope of about 54 to 60 mV per decade. See Figure 3. The electrode exhibits good time response (95% of total mV reading in 1 minute or less ) for carbon dioxide concentrations above 5 x 10...
Interferences Volatile weak acids are potential electrode interferences. Concentrations of these interfering species that cause a 10% error at M (44 ppm CO or 100 ppm CaCO ) and at pH 4 and 5 are listed in Table 5. Effects Of Dissolved Species Water vapor is a potential electrode interference.
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M to 10 M NaHCO +100 + 75 electrode + 50 potential (mV) + 25 M to 10 M NaHCO M to 5 X 10 M NaHCO time (minutes) Figure 4 Typical Electrode Response To Step Changes in Carbon Dixoide...
Theory of Operation The carbon dioxide electrode uses a gas-permeable membrane to separate the sample solution from the electrode internal solution. Dissolved carbon dioxide in the sample solution diffuses through the membrane until an equilibrium is reached between the partial pressure of CO in the sample solution and the CO in the internal...
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reference element outer body internal filling inner body solution membrane-spacer red O-ring assembly bottom cap sensing element Figure 5 Construction Of The Carbon Dixoide Electrode CO = % free species H CO Figure 6 Fraction of Carbonate, Bicarbonate, and Carbon Dixoide Ion As A Function Of pH...
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Chemistry of Carbon Dioxide Carbon dioxide reacts with water to form a weak carbonic acid solution: In basic solutions carbon dioxide exists as bicarbonate and carbonate: + OH- + 2OH- = + H The amount of carbon dioxide in the form of carbonate and bicarbonate depends on the pH of the solution.
The electrode is assembled using the flow-thru cap in place of the bottom cap supplied with the Orion 95-02 electrode (see Figure 7). When the electrode is placed in the electrode holder, it should be tilted at a 20° angle with respect to the support rod.
WARRANTY For the most current warranty information, visit www.thermo.com. The Thermo Electron Corporation, Orion products warranty covers failures due to manufacturer’s workmanship or material defects from the date of purchase by the user. User should return the warranty card and retain proof of purchase. Warranty is void if product has been abused, misused, or repairs attempted by unauthorized persons.
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Twenty-four months from date of purchase by the user (or thirty-six months from date of shipment from Thermo) • Orion ROSS Ultra ® Electrodes, Orion AQUAfast ® IV Colorimeters, Orion AQUAfast ® IV Turbidimeter, Orion 925 Flash Titrator ™ , Series 100 DuraProbe ™...
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Three months from date of purchase by the user (or six months from date of shipment from Thermo) • Economy Line Electrodes, Orion 91-05, 91-06, 91-15, 91-16, 91- 25, 91-26, 91-35, 91-36, 92-06. Warranty also includes failure for any reason (excluding breakage), except abuse, provided the electrode is not used in solutions containing silver, sulfide, perchlorate, or hydrofluoric acid;...
ORDERING INFORMATION Orion No. Description 950202 Internal Filling Solution, 50 mL bottle 950204 Membranes, box of four, with two O-rings 950206 Standard Solution, 0.1 M NaHCO 950207 Standard Solution, NaHCO , 1000 ppm as CaCO 950210 Carbon Dioxide Buffer Solution...
SPECIFICATIONS Concentration Range M to 10 M CO 4.4 to 400 ppm CO pH Range 4.8 to 5.2 pH Temperature Range 0˚ to 50˚C Electrode Resistance 1000 megohms Reproducibility ± 2% Sample Aqueous solutions only Size Electrode Length 151 mm Body Diameter 17 mm Cap Diameter...
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Environmental Instruments Water Analysis North America 166 Cummings Center Beverly, MA 01915 USA Tel: 978-232-6000 Dom. Fax: 978-232-6015 Int’l. Fax: 978-232-6031 Europe 12-16 Sedgeway Business Park Witchford, Cambridgeshire England, CB6 2HY Tel: 44-1353-666111 Fax: 44-1353-666001 Far East Room 904, Federal Building 369 Lockhart Road Wanchai, Hong Kong Tel: 852-2836-0981...
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