Cl - CHLORIDE ELECTRODE INSTRUCTION MANUAL. Model Thermo Orion. Thermo Orion Europe. Thermo Orion Far East. Thermo Orion Customer Support

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1 Cl - Model CHLORIDE ELECTRODE INSTRUCTION MANUAL Thermo Orion 500 Cummings Center Beverly, MA USA Tel: Dom. Fax: Int l. Fax: Thermo Orion Europe Sedgeway Business Park Witchford, Cambridgeshire England, CB6 2HY Tel: Fax: Thermo Orion Far East Room 904, Federal Building 369 Lockhart Road Wanchai, Hong Kong Tel: Fax: Thermo Orion Customer Support Toll Free: Dom. domcs1@thermoorion.com Int l. intcs1@thermoorion.com A Thermo Electron business Formerly Orion Research, Inc. A Thermo Electron business Formerly Orion Research, Inc rev. D

2 AQUAfast, Cahn, EZFlash, Ionalyzer, ionplus, KNIpHE, ORION, perphect, PerpHecT, PerpHecTion, phisa, phix, phuture, Pure Water, Sage, Sensing the Future, SensorLink, Sure-Flow, TEA Analyzer, Titrator PLUS, TURBO2 and Wine Master are registered trademarks of Thermo Orion pHAX-ION, A +, All in One, Aplus, AQUAsnap, AssuredAccuracy, AUTO-BAR, AUTOCAL, AUTO DISPENSER, Auto-ID, AUTO-LOG, AUTO-STIR, AUTO-READ, BOD AutoEZ, Cable-Free, CERTI-CAL, CISA, DataCOLLECT, DataPLUS, digital LogR, DirectCal, DuraProbe, Environmental Product Authority, Extra Easy/Extra Value, FAST QC, Flash GC, GAP, GLPcal, GLPcheck, GLPdoc, KAP, LabConnect, LogR, Minimum Stir Requirement, MSR, NISS, One-Touch, One-Touch Calibration, One-Touch Measurement, Optimum Results, Pentrode, phuture MMS, phuture Pentrode, phuture Quatrode, phuture Triode, Quatrode, QuiKcheK, rf link, ROSS, ROSS Resolution, SAOB, Stacked, Stat Face, The Enhanced Lab, ThermaSense, Triode, TRIUMpH, Unbreakable ph, Universal Access are trademarks of Thermo Orion. Guaranteed Success and The Technical Edge are service marks of Thermo Orion. PerpHecT meters are protected by U.S. patent 4,321,544. ROSS and PerpHecT ROSS are protected by U.S. patent 4,495,050. ORION Series A meters and 900A printer are protected by U.S. patents 5,108,578, 5,198,093, D334,208 and D346,753. ORION 81, 82, 91, and 92 series glass electrodes are protected by U.S. patents 4,661,236 and 4,687,500. Sure-Flow electrodes are protected by European Patent 278,979 and Canadian Patent 1,286,720. ionplus electrodes and Optimum Results solutions have patents pending. Copyright 2001, Thermo Orion. All rights reserved. The specifications, descriptions, drawings, ordering information and part numbers within this document are subject to change without notice. This publication supersedes all previous publications on this subject.

3 TABLE OF CONTENTS General Information 1 Introduction 1 Required Equipment 2 Required Solutions 2 Electrode Assembly 3 Packing List 3 Connecting Electrodes to Meter 4 Checking Electrode Operation with 701A Digital ph/mv Meter or 901 Ionalyzer 4 Checking Electrode Operation with 407A Specific Ion Meter 5 Measuring Hints 6 Using the electrode 8 Units of Measurement 8 Sample Requirements 8 Analytical Procedures 8 Direct Measurement Using 901 Ionalyzer 9 Direct Measurement Using 701A Digital ph/mv Meter 10 Low-Level measurements Using 701A Digital ph/mv Meter 11 Direct Measurement Using 407A Specific Ion Meter 12 Low-Level Measurements Using 407A Specific Ion Meter 13 Known addition 14 Using 901 Ionalyzer 14 Using 701A Digital ph/mv Meter 15 Using 407A Specific ion Meter 16 Troubleshooting 18 Troubleshooting Checklist 18 Assistance 20 Electrode characteristics 21 Electrode Response 21 Limits of Detection 22 Reproducibility 22 Temperature Effects 22 Interferences 24 Electrode Storage 24 Electrode Life 24 Theory of Operation 24 Ordering Information 28 Warranty 29 Specifications 33

4 GENERAL INFORMATION Introduction The Model chloride electrode allows chloride in aqueous solutions to be measured quickly, simply, accurately, and economically. All apparatus and solutions required for measurement, general analytical procedures, electrode characteristics, and electrode theory are discussed in this manual. The chloride electrode replaces Thermo Orion s chloride electrode. Most applications in technical journals, Thermo Orion Applications Bulletins, or Thermo Orion s Analytical Methods Guide that specify use of the can be performed with the electrode. Please call or write Technical Services at Thermo Orion for more information on specific applications. The chloride electrode is intended to measure chloride in the range of 1 x 10-5 M to 1 M. It can be used in the presence of modest concentrations of sulfide, iodide, and cyanide. For concentrated solutions and solutions in which nitrate or sulfate is present, the Thermo Orion solid-state Chloride Ion Electrode Model is recommended. 1

5 Required Equipment Meter Thermo Orion Model 901 Ionalyzer or 701A digital ph/mv meter for precision laboratory measurements, or Thermo Orion Model 407A specific ion meter for laboratory, field, or plant measurements. Reference electrode Thermo Orion Model double junction reference electrode with Thermo Orion Cat. No in the inner chamber. Do not use the outer chamber filling solution shipped with the reference electrode. Figure 1 Assembling the Electrode Electrode Body rubber washer Magnetic stirrer recommended for laboratory measurements. Graph paper (for use with digital ph/mv laboratory meters) 4-cycle semilogarithmic paper for preparing calibration curves. sensing module Required Solutions Distilled or deionized water to prepare all solutions and standards. Standard solution Thermo Orion 0.1 NaCl standard solution, Cat. No or Thermo Orion 100 ppm chloride standard solution, Cat. No Reference electrode outer chamber filling solution use 0.1 M KCl solution in the outer chamber. To prepare a 0.1 M KCl solution, place 0.75 g reagent-grade KCl in a 100 ml volumetric flask and dilute to volume with distilled water. Electrode Assembly Cut around the styrofoam package along the green line, remove top and take out the sealed glass vial. Remove the sensing module from the vial. Make sure the rubber washer on the sensing module is in place (See figure 1). Screw the sensing module into the electrode body until finger-tight. To insure electrical continuity, shake down the electrode in the manner of a clinical thermometer. Soak the electrode in distilled water for 10 minutes, then in a standard chloride solution (e.g M) until ready for usage. Packing List Two sensing modules in styrofoam packaging Electrode body electrode instruction manual 93 Series Methods Manual Warranty card 2 3

6 Connecting Electrodes to Meter Insert the reference electrode phone-tip connector and the sensing electrode connector into appropriate jacks on the digital ph/mv meter or specific ion meter. Non-Thermo Orion meters may require special adaptors. Consult your meter instruction manual. Checking Electrode Operation with 701A Digital ph/mv Meter or 901 Ionalyzer NOTE: Check electrodes daily. 1. Put 100 ml distilled water into a 150 ml beaker. Turn 701A Function Switch to MV position. Turn 901 Mode Switch to REL MV. Place electrodes in the solution. Press CLEAR/READ MV on the 901. If very drifty or unstable readings are observed, see the Troubleshooting Checklist. 2. Pipet 1 ml 0.1 M or 100 ppm standard into the solution. Stir thoroughly. When the reading is stable, read electrode potential in millivolts on the 701A and record. Press SET CONCN on the Add 10 ml 0.1 M or 100 ppm standard. Stir thoroughly. When the reading is stable, read electrode potential in millivolts and record. Determine the difference between the first and second potential readings on the 701A. Read the difference directly on the 901. Correct electrode operation is indicated by a difference of 56±2 mv assuming the solution temperature is between 20 and 25 C. If the change in potential is not within this range, see the Troubleshooting Checklist. Checking Electrode Operation with 407A Specific Ion Meter NOTE: Check electrodes daily. 1. Put 100 ml distilled water into a 250 ml beaker. Turn the Function Switch to the X-. Place electrodes in the solution. If very drifty or unstable readings are observed, see the Troubleshooting Checklist. 2. Pipet 1 ml 0.1 M or 100 ppm standard into the solution. Stir thoroughly. When the reading is stable, adjust the Calibration Control until the meter needle points to 1 at the center of the red logarithmic scale. 3. Add 10 ml 0.1 M or 100 ppm standard. Stir thoroughly. When the reading is stable, adjust the Temperature Compensator until the meter needle points to 10 at the far right of the red logarithmic scale. Turn the clear Slope Indicator dial until the white arrow on the Temperature Compensator points to the solution temperature. Read the percent electrode slope on the lower scale of the dial. Correct electrode operation is indicated by a percent slope between 90 and 100%. If the slope is not within this range, see the Troubleshooting Checklist. NOTE: The above procedure measures electrode slope. Slope is defined as the change in potential observed when the concentration changes by a factor of ten. 4 5

7 Measuring Hints Allow all standards and samples to come to ambient temperature for precise measurement. Stir samples and standards during measurement. For best results, stir at a rate that will not cause a vortex. Magnetic stirrers are recommended, but some models generate sufficient heat to change solution temperature. Place a piece of insulating material such as cork, cardboard, or styrofoam between the stirrer and heater. Between measurements, rinse and blot dry electrodes with a clean, dry tissue to prevent solution carryover. After immersion in solution, check electrode for any air bubbles on membrane surface and remove. If electrode response (see Electrode Response section) is slow, the membrane may contain a surface layer of contaminants. Restore performance by soaking electrodes in distilled water for about 5 minutes to clean membrane, then rinse and soak in a standard solution for about 5 minutes before use. For high ionic strength samples, prepare standards with composition similar to that of the sample. Concentrated samples (over 0.1 M) should be diluted before measurement. Figure 2 Typical Chloride Electrode Calibration Curve In the direct measurement procedure, a calibration curve is constructed on semilogarithmic paper. Electrode potentials of standard solutions are measured and plotted on the linear axis against their concentrations on the log axis. In the linear regions of the curves, only three standards are needed to determine a calibration curve. In non-linear regions, more points must be taken. The direct measurement procedures in the manual are given for concentrations in the region of linear electrode response. Low-level measurement procedures are given for measurements in the non-linear region. 6 7

8 USING THE ELECTRODE Units of Measurement Chloride can be measured in units of moles per liter, parts per million, or any other convenient concentration unit (see table 1) Sample Requirements Sample must be aqueous; they must not contain organic solvents which can dissolve in or remove the liquid ion exchanger, causing the electrode to fail. Consult Thermo Orion s Technical Service Department for using the electrode in specific applications. Samples and standards should be at the same temperature. A 1 C difference in temperature will give rise to about a 2% measurement error. Temperature must be less than 40 C. Interferences should be absent; see table 5, for a list of interferences. Electrodes exposed to high interferences will drift for several hours on returning the electrode to a chloride standardizing solution. Analytical Procedures Direct measurement is a simple procedure for measuring a large number of samples. Only one meter reading is required for each sample. The temperature of samples and standards should be the same. Known addition (see Known Addition section) measures total chloride concentration in the absence of, or in the presence of, a large excess (50 to 100 times) of, complexing agent. Since no calibration is necessary, know addition is a convenient method for measuring occasional samples. Direct Measurement Using 901 Ionalyzer 1. Prepare a standard solution whose concentration is near the expected sample concentration. If samples fall in the nonlinear region of electrode response (see figure 2), prepare a blank solution of 100 ml distilled water. If desired, prepare a different standard solution for verifying electrode slope. 2. Place electrodes in the standard solution. Stir thoroughly. Turn the Mode Switch to CONCN and set the STD VALUE switches to the concentration of the standard. Set the SLOPE switches to the slope of the electrode determined in the daily slope check. Turn the sign of the slope to minus. If SET BLANK is lighted, press to turn off. 3. Press CLEAR/READ mv. When the absolute potential reading is stable, press SET CONCN. Rinse electrodes, blot dry. 4. If low-level measurements are to be done, place electrodes in the blank solution. Stir thoroughly. Wait one minute and press SET BLANK. 5. Check the slope setting if desired. Place electrodes in a second standard and stir thoroughly. When the reading is stable, slowly adjust the SLOPE switches until the standard concentration is displayed. Rinse electrodes, blot dry. 6. Transfer 100 ml sample to a 150 ml beaker. Stir thoroughly. Place electrodes in solution, wait until the reading is stable, and read the concentration directly. 7. Recalibrate every 2 hours. Place electrodes in the first standard, and proceed as in step 3. If the ambient temperature has changed, change the SLOPE switch by 1 mv per 5 C change (higher temperatures correspond to larger slopes). Table 1 Concentration Unit Conversion Factors moles per liter ppm as Cl - ppm as NaCl

9 Direct Measurement Using 701A Digital ph/mv Meter 1. Prepare 10-2, 10-3, and 10-4 M Cl - or 100, 10, and 1 ppm Cl - standards by serial dilution of the 0.1 M or 100 ppm standard. If samples have an ionic strength above 0.1 M, prepare standards with a composition similar to samples. 2. Place electrodes in the 10-4 M or 1 ppm standard. Set the Function Switch to MV. Stir thoroughly, wait for a stable potential reading, and record. 3. Rinse electrodes, blot dry, and place in the 10-3 M or 10 ppm standard. Stir thoroughly, wait for a stable potential reading, and record. 4. Rinse electrodes, blot dry, and place in the 10-2 M or 100 ppm standard. Stir thoroughly, wait for a stable potential reading, and record. 5. Plot the millivolt readings (linear axis) against concentration (log axis) on standard 4-cycle semilogarithmic paper. See the typical calibration curve in figure 2. The calibration curve may be extrapolated down to about 5 x 10-5 M (1.75 ppm as chloride). 6. Transfer 50 to 100 ml of sample to a 150 ml beaker. 7. Rinse electrodes, blot dry, and place in sample. Stir thoroughly. Record the millivolt reading, when stable. Determine the unknown concentration from the calibration curve. 8. Recalibrate after 1 to 2 hours of use. If the ambient temperature has not changed, simply place electrodes in the midrange standard. When the reading is stable, compare to the original reading recorded in step 3 above. If readings differ by more than 0.5 mv or if the ambient temperature has changed, repeat steps 2-5 above. Prepare a new calibration curve daily. Low-Level Measurements Using 701A Digital ph/mv Meter The following procedure is for solutions with ionic strength less than 10-2 M. For solutions low in chloride but high in ionic strength, perform the same procedure with one change: prepare a calibration solution (step 2) with a composition similar to samples. 1. For measurements in moles per liter, dilute 1 ml 0.1 M standard to 100 ml to prepare a 10-3 M Cl - solution. For measurements in ppm, prepare a 10 ppm Cl - solution by diluting 10 ml of the 100 ppm standard to 100 ml. Prepare standards fresh each day. 2. Prepare a 100 ml distilled water solution in a volumetric flask. Transfer this calibration solution to a 150 ml beaker. Add increments of the 10-3 M or 10 ppm standard as described in table 2. Stir thoroughly after each addition and record the electrode potential when stable. 3. Plot on semilog paper the electrode potential (linear axis) versus concentration (log axis) as in figure Rinse electrodes, blot dry, and place in sample. Stir thoroughly. When the reading is stable, determine the concentration from the low-level calibration curve. 5. Recalibrate after 1 to 2 hours of use by repeating steps 1-4 above. Prepare a new low-level calibration curve daily. Table 2 Calibration Curve for Low-Level Measurements Additions of 10 ppm Cl - or 10-3 M Cl - standard to 100 ml of distilled water. A is a 1 ml graduated pipet. B is a 2 ml pipet. added concentration: step pipet volume ppm (Cl - ) molarity Cl - 1 A 0.1 ml x A x A x A x A x B x B x

10 Direct Measurement Using 407A Specific Ion Meter 1. Prepare 10-2 M and 10-3 M Cl - or 100 ppm and 10 ppm Cl - standards by serial dilution of the 0.1 M or 100 ppm standard. If samples have a high ionic strength, above 0.1 M, prepare standards with a composition similar to the samples. 2. Place electrodes in the 10-3 M or 10 ppm standard. Turn the Function Switch to X -. Stir thoroughly. When the reading is stable, adjust the meter needle to 1 (center scale) on the red logarithmic scale with the Calibration Control. 3. Rinse electrodes, blot dry, and place in the 10-2 M or 100 ppm standard. Stir thoroughly. When the reading is stable, turn the Temperature Compensator knob until the meter needle reads 10 (full-scale right) on the red logarithmic scale. 4. Transfer 50 to 100 ml of sample to a 150 ml beaker. 5. Rinse electrodes, blot dry, and place in the sample. Stir thoroughly. When the reading is stable, multiply the meter reading on the red logarithmic scale by 10-3 to determine sample concentration in moles per liter, or by 10 to determine the sample concentration in ppm Cl Recalibrate every 1 to 2 hours. If the ambient temperature has not changed, repeat step 2. If the temperature has changed, repeat steps 2 and 3. Off-Scale Readings in Sample If the needle goes off-scale right, rinse the electrodes, blot dry, and place them in the 10-2 M or 100 ppm standard. Adjust the Calibration Control until the needle points to 1 (center scale) on the red logarithmic scale. Rinse the electrodes, blot dry, and replace in sample. Stir thoroughly. When the reading is stable, multiply the meter reading on the red logarithmic scale by 10-2 to determine sample concentration in moles per liter, or by 100 to determine sample concentration in ppm Cl - If the needle goes off-scale left, rinse the electrodes, blot dry, and place in 10-3 M or 10 ppm standard. Stir thoroughly. When the reading is stable, adjust the Calibration Control until the needle points to 10 (full-scale right) on the red logarithmic scale. Rinse the electrodes, blot dry, and replace in sample. Stir thoroughly. When the reading is stable, multiply the meter reading on the red logarithmic scale by 10-4 M to determine sample concentration in moles per liter. The sample concentration in ppm Cl - can be read directly from the meter. Low-Level Measurements Using 407A Specific Ion Meter The following procedure is for solutions with ionic strength less than 10-2 M. For solutions low in chloride but high in ionic strength, perform the same procedure with one change: prepare standards and blank (step 4) with a composition similar to the sample. 1. Prepare 10-3 M and 10-4 M Cl - or 10 ppm and 1 ppm Cl - standards by serial dilution of the 0.1 M or 100 ppm standard. 2. Turn the Function Switch to X -. Place the electrodes in the more dilute standard. Stir thoroughly. When the reading is stable, adjust the meter needle to 1 (center scale) on the red logarithmic scale with the Calibration Control. Rinse electrodes, blot dry, and place them in the more concentrated standard. Stir thoroughly. When the reading is stable, turn the Temperature Compensator knob until the meter needle reads 10 (full-scale right) on the red logarithmic scale. 3. Rinse electrodes, blot dry, and place them in the more dilute standard. Stir thoroughly. When the reading is stable, adjust the Calibration Control until the meter reads 10 (full-scale right) on the red logarithmic scale. 4. Rinse electrodes, blot dry, and place in 100 ml distilled water. Stir thoroughly. When the reading is stable, record the blank correction, A, on the red logarithmic scale. 5. Transfer 50 to 100 ml sample to a 150 ml beaker. 6. Rinse electrodes, blot dry, and place in sample. Stir thoroughly. When the reading is stable, record the reading on the red logarithmic scale and subtract A from this reading. If moles per liter is used, multiply the result by 10-5 to find sample concentration. If ppm is the concentration unit used, divide the result by 10 to find the sample concentration. 7. Recalibrate every 1 or 2 hours. If the ambient temperature has not changed, repeat step 3. If the temperature has changed, repeat steps 2 and

11 Known Addition Known addition is convenient for measuring occasional samples because no calibration is needed. Since an accurate measurement requires that the concentration double as a result of the addition, sample concentration must be known within a factor of three. Total concentration of chloride is measured in the absence of complexing agents or in the presence of a large excess (50 to 100 times). Complexing agent may be added, if necessary. Known addition is a convenient check on the results of direct measurement. Using 901 Digital Ionalyzer 1. Set Mode Switch to desired known addition mode: KA/1, KA/5, or KA/10. The KA/1 mode is not recommended for precise measurements because of possible pipeting errors. Set the SLOPE switches to the slope as determined in the daily electrode check, and set the Sign Switch to minus. 2. Depending on expected sample concentration and the mode selected, prepare a standard solution: Mode KA/1 KA/5 KA/10 Concentration approximately 100 x sample approximately 20 x sample approximately 10 x sample Set the STD VALUE switches to the concentration of the standard. 3. If low-level measurements are being made, prepare a blank solution of 100 ml distilled water. Place electrodes in the blank solution, stir thoroughly, and press CLEAR/READ mv. When the reading is stable, press SET CONCN. The reading may become unstable, especially in the KA/1 mode. Add 1 (KA/1), 5 (KA/1), 5 (KA/5), or 10 (KA/10) ml standard to the blank. Stir thoroughly. When the reading is stable, press SET BLANK. The blank correction is stored for use in repeated measurements. 4. Place electrodes in 100 ml sample. Stir thoroughly. Press CLEAR/READ mv. When the reading is stable, press SET CONCN. The reading may become unstable, especially in the KA/1 mode. 5. Add 1(KA/1), 5 (KA/5), or 10 (KA/10) ml standard. Stir thoroughly. When the reading is stable, read sample concentration directly from the meter. Using 701A Digital ph/mv Meter To measure an unknown sample, place electrodes in 100 ml sample. Stir thoroughly. Follow steps 1 through 4 below. To check the results of a direct measurement, leave the electrodes in 100 ml sample and follow steps 1 through 4 below. 1. Turn the Function Switch of the meter to REL MV. When the reading is stable, set the reading to by turning the Calibration Control. If the reading cannot be set to 000.0, record the potential reading. 2. Prepare a standard solution about 10 times as concentrated as the sample concentration by diluting 0.1 M or 100 ppm standard. 3. Pipet 10 ml standard into the sample. Stir thoroughly. When the reading is stable, record the potential difference, E. If the meter could not be zeroed in step 1, subtract the second reading from the first to find E. 4. 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: C o where: C o Q C S = QC S = sample concentration = reading from known addition table = concentration of added standard 14 15

12 Table 3 Known addition table, values for Q vs. E at 25 C (59 mv slope) for 10% volume change E Q E Q E Q E Q Using 407A Specific Ion Meter To measure an unknown sample, place electrodes in 100 ml of sample. Stir thoroughly. Turn the Function Switch to X -, set the Slope Indicator dial to the percent slope determined in the daily checkout, and turn the Temperature Compensator knob to the sample temperature. Follow steps 1 through 4 below. To check the results of a direct measurement, leave the electrodes in 100 ml of sample and follow steps 1 through 4 below. 1. When the reading is stable, set the needle to on the green increment scale by turning the Calibration Control. 2. Prepare a standard solution about 100 times as concentrated as the sample concentration by diluting the 0.1 M standard or 100 ppm standard. 3. Pipet 1 ml standard solution into 100 ml sample. Stir thoroughly. When the reading is stable, record the reading, Q, from the green increment scale. 4. To determine the original sample concentration, use the following equation: C o where: C o Q C S = (Q/100)C S = sample concentration = reading from green increment scale = concentration of added standard

13 TROUBLESHOOTING Troubleshooting Checklist Symptom Off-Scale or Over-Range Reading Noisy or Unstable Readings (readings continuously or rapidly changing) Drift (reading slowly changing in one direction) Low Slope or No Slope Wrong Answer (but calibration curve is OK ) Possible Causes Defective meter Defective sensing module Electrodes not plugged in properly Module not installed properly Reference electrode junction is dry Reference electrode not filled Air bubble on membrane Calibration control not turned far enough Defective meter Module not installed properly Air bubble on membrane Wrong reference electrode Meter or stirrer not grounded Samples and standards at different temperatures Electrode exposed to interferences Incorrect reference filling solution Standards contaminated or incorrectly made Defective sensing module Electrode exposed to interferences Incorrect scaling of semi-log paper Incorrect sign 407A function switch in wrong position 407A incorrectly calibrated Incorrect standards Wrong units used Complexing agents in sample Next Step Check meter with shorting strap (see meter instruction manual) Check Electrode Operation Unplug electrodes and reseat Check Electrode Assembly, figure 1 Hold cap and lift outer sleeve to expel a few drops of filling solution Be sure reference electrode is filled Remove bubble by redipping electrode Continue turning the calibration control. It provides 10 turns of coarse calibration range, and is more difficult to turn after the 270 fine tuning range has been exceeded Check meter with shorting strap Check Electrode Assembly, figure 1 Remove bubble by redipping electrode Do not use calomel or Ag/AgCl (frit- or fiber-type) reference electrode Ground meter or stirrer Allow solutions to come to room temperature before measurement Soak electrode in chloride standard (electrode assembly, page 3) Use recommended filling solution Prepare fresh standards Check Electrode Operation Soak electrode in chloride standard (Electrode Assembly) Plot millivolts on the linear axis. On the log axis, be sure concentration numbers within each decade are increasing with increasing concentration. Be sure to note sign of millivolt number correctly Set function switch to X - position Set first standard to a center scale reading with the calibration knob, Second standard to the end of the scale with the temperature knob Prepare fresh standards Apply correct conversion factor: 10-3 M = 35.5 ppm as Cl - = 58.5 ppm as NaCl Use known addition, or decomplexing procedure 18 19

14 ELECTRODE CHARACTERISTICS Assistance If after checking each component of your measuring system the source of the trouble remains unknown, call Thermo Orion s Technical Service Chemists: In the United States (except Massachusetts, Alaska, and Hawaii) In Massachusetts, Alaska or Canada, Call Elsewhere, contact your authorized Thermo Orion dealer or: Thermo Orion 500 Cummings Center Beverly, MA USA Tel: Dom. Fax: Int l. Fax: Electrode Response The electrode potential plotted against concentration on semilogarithmic paper results in a straight line with a slope of about 56 mv per decade. See figure 2. The electrode exhibits good time response (99% response in one minute or less) for chloride concentrations above 10-4 M. Below this value response times vary from 2 to 5 minutes. See figure 4. Response time is more rapid when going from dilute to concentrated solutions than in the other direction. Figure 4 Typical Electrode Response to Step Changes in NaCl Thermo Orion Europe Sedgeway Business Park Witchford, Cambridgeshire England, CB6 2HY Tel: Fax: Thermo Orion Far East Room 904, Federal Building 369 Lockhart Road Wanchai, Hong Kong Tel: Fax: Thermo Orion Customer Support Toll Free: Dom. domcs1@thermoorion.com Int l. intcs1@thermoorion.com 20 21

15 Limits of Detection In pure sodium chloride solutions, the upper limit of detection is 1 M. When other ions are present, the upper limit of detection is above 10-1 M chloride, but is influenced by two factors the possibility of a liquid junction potential developing at the reference electrode and the salt extraction effect. At high salt concentrations, some salts may be extracted into the electrode membrane, causing deviation from theoretical response. To measure samples between 10-1 and 1 M, calibrate the electrode at 4 or 5 intermediate points, or dilute the sample. The lower limit of detection is determined by the very slight water solubility of the ion exchanger in the sensing module, which causes deviation from theoretical response. Figure 2, shows the theoretical response at low levels of sodium choride compared to the actual response. If chloride measurements are made below 5 x 10-5 M Cl - (1.75 ppm as Cl - or 2.90 ppm as NaCl), a low-level measurement procedure is recommended. Reproducibility Reproducibility is limited by factors such as temperature fluctuations, drift, and noise. Within the electrode s operating range, reproducibility is independent of concentration. With calibration every hour, direct electrode measurements reproducible to ±2% can be obtained. Temperature Effects Since electrode potentials are affected by changes in temperature, samples and standard solutions should be within ±1 C (±2 F) of each other. At the 10-3 M level, a 1 C difference in temperature results in a 2% error. The absolute potential of the reference electrode changes slowly with temperature because of the solubility equilibria on which the electrode depends. The slope of the chloride electrode also varies with temperature, as indicated by the factor S in the NERNST equation. Values of the Nernst factor for chloride ion are given in table 4. If temperature changes occur, meter and electrodes should be recalibrated. The electrode can be used at temperatures from 0 to 40 C, provided that temperature equilibrium has occurred. For use at temperatures substantially different from room temperature, equilibrium times up to an hour are recommended. Table 4 Values of Theoretical Electrode Slope vs. Temperature T C S T C S Table 5 Levels of Possible Interferences Causing a 10% Error at Various Levels of Sodium Chloride Interferences (moles per liter) 10-4 M 10-3 M 10-2 M Cl - - ClO 4 1 x x x 10-5 I - 5 x x x NO 3 5 x x x 10-4 OH - 1 x x x 10-3 = SO 4 2 x x x 10-3 Br - 1 x x x HCO 3 1 x x x 10-2 OAC - 3 x x x 10-2 F - 7 x x x 10-2 Interferences (ppm) 1 ppm 10 ppm 100 ppm Cl - - ClO 4 3 x x I NO 3 9 x OH - 5 x = SO Br HCO OAC F

16 Interferences Some other anions, if present at high enough levels, are electrode interferences and will cause measurement errors or electrode malfunction. Table 5 indicates levels of common anions that will cause 10% error at three levels of chloride. The top half of the table shows interference levels in moles per liter at 10-4, 10-3, and 10-2 M concentrations of chloride. The bottom half of the table shows interference levels in ppm at 100, 10, and 1 ppm chloride. In cases where the electrode is exposed to high levels of interfering ions, it may become drifty and sluggish in response. When this happens, restore normal performance by soaking for an hour in distilled water, then for a few hours in chloride standard solution. Electrode Storage The sensing module should be kept in the glass vial until it is to be used. The assembled electrode can be stored in 10-2 M chloride solution. For long periods of time (over 2-3 weeks), disassemble the electrode and store the module in its vial. Be sure to rinse and refill a stored reference electrode before attempting measurements. Electrode Life Each sensing module should last at least six months in normal laboratory use. In time electrode slope will decrease and readings will start to drift, indicating that the module should be changed. Before replacement, refer to the Troubleshooting Checklist, to make sure that the difficulties are caused by the sensing module. Theory of Operation The chloride electrode consists of an electrode body and a replaceable pretested sensing module. The sensing module contains a liquid internal filling solution in contact with a gelled organophilic membrane containing a chloride ion-selective ion exchanger. See figure 5. Figure 5 Construction of Electrode Sensing Module When the membrane is in contact with a chloride solution, an electrode potential develops across the membrane. This potential, which depends on the level of free chloride ion in solution, is measured against a constant reference potential with a digital ph/mv meter or specific ion meter. The measured potential corresponding to the level of the chloride ion in solution is described by the Nernst equation: E where: E E o A S = E o S log (A) = measured electrode potential = reference potential (a constant) = chloride ion level in solution = electrode slope (about 56 mv per decade) The level of chloride ion, A is the activity or effective concentration of free chloride ion in solution

17 The total chloride concentration, C t includes some bound or complexed ions as well as free chloride ions. The electrode responds only to the free ions, whose concentration is: C f = C t C b where C b is the concentration of chloride ions in all bound or complexed forms. (Fortunately, chloride ions form very few stable complexes, so that the free chloride ion concentration (C f ) may be taken as equal to the total chloride ion concentration (C t ).) The chloride ion activity is related to free chloride ion concentration by the activity coefficient, γ: A = γc f Ionic activity coefficients are variable and largely depend on total ionic strength. Ionic strength is defined as: Ionic strength = 1/2 C i Z i 2 where: C i Z i = concentration of ion i = charge of ion i If the background ionic strength is high and constant relative to the sensed ion concentration, the activity coefficient is constant and activity is directly proportional to concentration. Reference electrode condition must also be considered. Liquid junction potentials arise any time two solutions of different composition are brought into contact. The potential results from the interdiffusion of ions in the two solutions. Since ions diffuse at different rates, electrode charge will be carried unequally across the solution boundary resulting in a potential difference between the two solutions. In making electrode measurements it is important that this potential be the same when the reference is in the standardizing solution as well as in the sample solution; otherwise, the change in liquid junction potential will appear as an error in the measured specific ion electrode potential. The most important variable which the analyst has under his control is the composition of the liquid junction filling solution. The filling solution should be equitransferent. That is, the speed with which the positive and negative ions in the filling solution diffuse into the sample should be as nearly equal as possible. If the rate at which positive and negative charge is carried into the sample solution is equal then no junction potential can result. However, there are a few samples where no filling solution adequately fulfills the condition stated above. Particularly troublesome are samples containing high levels of strong acids (ph 0-2) or strong bases (ph 12-14). The high mobility of hydrogen and hydroxide ions in samples makes it impossible to swamp out their effect on the junction potential with any concentration of an equitransferent salt. For these solutions it is recommended to: calibrate in the same ph range as the sample; or, use a known increment method for ion measurement. For more information, call Technical Services at Thermo Orion

18 ORDERING INFORMATION WARRANTY Chloride electrode with two sensing modules Replacement electrode sensing module for chloride electrode Chloride standard solution (0.1 M), 1 pint Chloride standard solution (100 ppm as chloride), 1 pint Microsample dish Double junction reference electrode Model 407A/F portable specific ion meter Model 407A/L specific ion meter for laboratory use Model 701A digital ph/mv meter Model 901 digital Ionalyzer Electrode arm with swivel base The Thermo Orion 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 to Thermo Orion and retain proof of purchase. Warranty is void if product has been abused, misused, or repairs attempted by unauthorized persons. Warranties herein are for product sold/installed by Thermo Orion or its authorized dealers. Any product sold by a U.S. or Canadian distributor must be returned to Thermo Orion for any warranty work. A Return Authorization Number must be obtained from Thermo Orion Laboratory Technical Service before returning any product for in-warranty repair or replacement. In the event of failure within the warranty period, Thermo Orion will at Thermo Orion s option, repair or replace product not conforming to this warranty. There may be additional charges, including freight, for warranty service performed in some countries. For service, call Thermo Orion (or its authorized dealer outside the United States and Canada). Thermo Orion reserves the right to ask for proof of purchase, such as the original invoice or packing slip. Laboratory ph Meters (Models 611 and 301), SensorLink, PerpHecT ph/ise Meters, phuture ph Meters (Models 610 and 620), Sage Pumps, Cahn Balances, 930 Ionalyzer, 950 ROSS FAST QC Titrator, 960 Titrator PLUS, Karl Fischer Titrators, Autosamplers, Liquid Handling Devices, phuture Conversion Box, Wine Master, 607 Switchbox, rf link, AQUAfast II Colorimeters, Vacuum Degasser, Flowmeter are warranted to be free from defects in material and workmanship for a period of twelve (12) months from the date of purchase by the user or eighteen (18) months from date of shipment from Thermo Orion, whichever is earlier, provided use is in accordance with the operating limitations and maintenance procedures in the instruction manual and when not having been subjected to accident, alteration, misuse, or abuse. The warranty period for 960 Titrator PLUS, 950 Fast QC Titrator, Wine Master and 930 Ionalyzer pumps is three (3) months from date of purchase

19 Economy Line Electrodes, Models 91-05, 91-06, 91-15, 91-16, 91-25, 91-26, 91-35, 91-36, 92-06, are warranted to be free from defects in material and workmanship for a period of three (3) months from date of purchase by customer or six (6) months from date of shipment from Thermo Orion, whichever is earlier. 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; or in solutions more than one (1) Molar in strong acid or base at temperatures above 50 C. Ion Selective Electrodes, ionplus Electrodes, ROSS Electrodes, Sure-Flow Electrodes, PerpHecT Electrodes, AquaPro Professional Electrodes, Standard Line ph Electrodes, Tris ph Electrodes, ORP Triode (Cat. No. 9180BN), phuture ph Probes (Cat. No ) and phuture MMS Quatrode and Triode (Cat. Nos and ), Model DO Probe, Series 100 Conventional Conductivity Cells, temperature probes and compensators (except those models noted) are warranted to be free from defects in material and workmanship for a period of twelve (12) months from the date of purchase by the customer or eighteen (18) months from date of shipment from Thermo Orion, whichever is earlier, except for abuse or breakage of electrodes. 93 and 97 ionplus Series sensing modules are warranted to give six (6) months of operation if placed in service before the date indicated on the package, except and Nitrate modules are warranted to give ninety (90) days of operation if placed in service before the date indicated on the package. Thermo Orion phuture (Cat. No ) and phuture MMS Pentrode (Cat. No ), Quatrode (Cat. No ) and Triode (Cat. No ), Low Maintenance Triode (Cat. No. 9107BN), ORP Low Maintenance Triode (Cat. No. 9179BN), and PerpHecT Low Maintenance Triode (Cat. No. 9207BN), Waterproof Triode (Cat. No. 9107WP, 9107WL, 9109WL, 9109WP), QuiKcheK Meters, Micro Electrodes are warranted to be free from defects in material and workmanship for a period of six (6) months from date of purchase by the customer or twelve (12) months from date of shipment from Thermo Orion, whichever is earlier when used in accordance with the operating limitations and maintenance procedure in the instruction manual and when not having been subjected to accident, alteration, misuse or abuse. AQUAfast IV colorimeters, Series 100 DuraProbe Conductivity Cells and Series 800 Dissolved Oxygen Probes are warranted to be free from defects in material and workmanship for a period of twenty-four (24) months from the date of purchase by the user or thirty (30) months from the date of shipment from Thermo Orion, whichever is earlier, provided use is in accordance with the operating limitations and maintenance procedures in the instruction manual and when not having been subjected to accident, alteration, misuse, or abuse. Waterproof meters (Models 630, 635, 830A, 835A, 260A, 261S, 265A, 266S, 130A, 131S, 135A, 136S, 1230, 142 and 842), Conductivity meters (Models 105Aplus, 115Aplus, 125Aplus, 145Aplus, 150Aplus and 162A), phuture MMS meters (Models 535A, 555A), ph/conductivity meter (Model 550A), Dissolved Oxygen meters (Models 810Aplus, 850Aplus and 862A), are warranted to be free from defects in material and workmanship for a period of thirty-six (36) months from the date of purchase by the user or forty-two (42) months from date of shipment from Thermo Orion, whichever is earlier, provided use is in accordance with the operating limitations and maintenance procedures in the instruction manual and when not having been subjected to accident, alteration, misuse or abuse. LabConnect and DataCOLLECT carry an out-of-box warranty. Should they fail to work when first used, contact Thermo Orion immediately for replacement. Thermo Orion Meter, Electrode, Analytical System Accessories, Solutions, AQUAfast Test Strips, AQUAfast II and IV Reagent Kits and accessories, Series 800 Dissolved Oxygen Probe Membranes and Cahn Balance Accessories such as cables, printers, and line adapters carry an out-of-box warranty. Should they fail to work when first used, contact Thermo Orion immediately for replacement. Should Thermo Orion Solutions or Buffers be unusable when first out-of-box, contact Thermo Orion immediately for replacement. For products not listed in this warranty statement, please visit our website: thermoorion.com

20 SPECIFICATIONS THE WARRANTIES DESCRIBED ABOVE ARE EXCLUSIVE AND IN LIEU OF ALL OTHER WARRANTIES WHETHER STATUTORY, EXPRESS OR IMPLIED INCLUDING, BUT NO LIMITED TO, ANY IMPLIED WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE AND ALL WARRANTIES ARISING FROM THE COURSE OF DEALING OR USAGE OF TRADE. THE BUYER S SOLE AND EXCLUSIVE REMEDY IS FOR REPAIR OR REPLACEMENT OF THE NON-CONFORMING PRODUCT OR PART THEREOF, OR REFUND OF THE PURCHASE PRICE, BUT IN NO EVENT SHALL THERMO ORION (ITS CONTRACTORS AND SUPPLIERS OF ANY TIER) BE LIABLE TO THE BUYER OR ANY PERSON FOR ANY SPECIAL, INDIRECT, INCIDENTAL, OR CONSEQUENTIAL DAMAGES WHETHER THE CLAIMS ARE BASED IN CONTRACT, IN TORT (INCLUDING NEGLIGENCE), OR OTHERWISE WITH RESPECT TO OR ARISING OUT OF THE PRODUCT FURNISHED HEREUNDER. REPRESENTATION AND WARRANTIES MADE BY ANY PERSON, INCLUDING ITS AUTHORIZED DEALERS, REPRESENTATIVES AND EMPLOYEES OF THERMO ORION WHICH ALTER OR ARE IN ADDITION TO THE TERMS OF THIS WARRANTY SHALL NOT BE BINDING UPON THERMO ORION UNLESS IN WRITING AND SIGNED BY ONE OF ITS OFFICERS. Note: For in- or out-of-warranty repair or service, contact Thermo Orion Technical Service (or its authorized dealer outside the United States and Canada). Technical Service will issue a Return Authorization (RA) for all repair services. You must have an Thermo Orion RA prior to returning/forwarding any product to Thermo Orion. Concentration range ph range 5 x 10-6 M to 1 M (0.18 to 35,000 ppm as Cl - ) 3.5 to 9 ph* Temperature range 0 to 40 C Electrode resistance Reproducibility ±2% Sample Minimum sample size Storage Module life Size *See page 27 1 to 5 megohms Aqueous solutions only 3 ml in a 50 ml beaker, 0.3 ml in Thermo Orion Microsample Dish (Cat. No ) Store in chloride standard Six months under normal laboratory conditions Electrode length: 13.5 cm Diameter: 1.2 cm Cap diameter: 1.6 cm Cable length: 100 cm specifications subject to change without notice 32 33

21 NOTE 34