Instruction Manual Cyanide Electrode EUTECH INSTRUMENTS PTE LTD. INSTRUCTION MANUAL CYANIDE ION ELECTRODE 1 Cyanide Electrode Instruction Manual TABLE OF CONTENTS GENERAL INSTRUCTIONS .......................................................................................................... 3 Introduction ..............................................................................................................................................3 Required Equipment.................................................................................................................................3 Required Solutions ...................................................................................................................................3 GENERAL PREPARATION............................................................................................................ 4 Electrode Preparation ...............................................................................................................................4 Electrode Slope Check (with pH/mV meter) ...........................................................................................4 Electrode Slope Check (with an ion meter)..............................................................................................4 MEASUREMENT.............................................................................................................................. 5 Measuring Hints .......................................................................................................................................5 Sample Requirements...............................................................................................................................5 Units of Measurement ..............................................................................................................................6 MEASUREMENT PROCEDURE ................................................................................................... 6 Direct Measurement .................................................................................................................................6 Direct Measurement of Cyanide (using a pH/mV meter) ........................................................................6 Direct Measurement of Cyanide (using an ion meter) .............................................................................7 Low-Level Cyanide Measurements (using a pH/mV meter)....................................................................8 ELECTRODE CHARACTERISTICS............................................................................................. 9 Reproducibility.........................................................................................................................................9 Interferences .............................................................................................................................................9 Complexation .........................................................................................................................................10 Temperature Influences..........................................................................................................................10 Electrode Response ................................................................................................................................11 Limits of Detection.................................................................................................................................12 pH Effects...............................................................................................................................................12 Electrode Life.........................................................................................................................................12 Electrode Storage ...................................................................................................................................12 ELECTRODE THEORY ................................................................................................................ 12 Electrode Operation ...............................................................................................................................13 TROUBLESHOOTING GUIDE .................................................................................................... 14 Meter ......................................................................................................................................................14 Plastic-ware ............................................................................................................................................14 Electrodes...............................................................................................................................................14 Standards and Reagents..........................................................................................................................15 Sample....................................................................................................................................................15 Technique...............................................................................................................................................15 TROUBLESHOOTING HINTS..................................................................................................... 16 SPECIFICATIONS.......................................................................................................................... 18 ORDERING INFORMATION....................................................................................................... 18 2 Instruction Manual Cyanide Electrode EUTECH INSTRUMENTS PTE LTD. CYANIDE ION ELECTRODE INSTRUCTION MANUAL GENERAL INSTRUCTIONS Introduction Eutech Instruments Cyanide Ion Electrode is used to measure cyanide ions in aqueous solutions quickly, simply, accurately, and economically. *IMPORTANT NOTICE* Acidic cyanide solutions produce hydrogen cyanide (HCN) gas, highly toxic whether breathed or absorbed through the skin. Use of the proper and recommended ionic strength adjuster (ISA) will keep the solution pH above 10. If measurements in acidic solution are necessary (decomplexing procedure as given in the section Complexation), THIS PROCEDURE MUST BE DONE IN A FUME HOOD. Use a pipet bulb when pipeting cyanide solutions, as these solutions are highly toxic. Required Equipment 1. 2. A pH/mV meter or an ion meter, either line operated or portable. Semi-logarithmic 4-cycle graph paper for preparing calibration curves when using the meter in the mV mode. A magnetic stirrer. Eutech Cyanide Ion Combination Epoxy-body Electrode, Code no. EC-CN-03. Lab-ware made of plastic, not glass. Polishing Paper, Code no. EC-MIS-PP, to polish dirty or etched electrode membranes. 3. 4. 5. 6. Required Solutions 1. 2. Deionized or distilled water for solution and standard preparation. Eutech Cyanide Ionic Strength Adjuster (ISA), 10M NaOH, Code no. EC-ISA-CN1-BT. To prepare the ISA from your own laboratory stock, fill a 1,000 ml beaker with about 900 ml of distilled water. While gently stirring the solution under a hood, slowly add 400 grams of reagent-grade sodium hydroxide. Transfer the solution quantitatively to a one liter volumetric flask after the solid NaOH has dissolved and the beaker has cooled. Dilute to the mark with distilled water, cap, and upend several times to thoroughly mix the solution. Store in a plastic bottle. 3 Cyanide Electrode Instruction Manual 3. Cyanide Standard, 1X10-2M. To prepare this solution from your own laboratory stock, add 10 ml of ISA and about 500 ml of distilled water to a one liter volumetric flask. Add 0.49 grams of dry, reagent-grade sodium cyanide, NaCN, to the solution and swirl the flask gently to dissolve the solid. Dilute to the mark with distilled water, cap, and upend the flask several times to thoroughly mix the contents. Store all standards in plastic bottles and prepare weekly. Cyanide Standard, 1,000 ppm. To prepare this solution from your own laboratory stock, add 10 ml of ISA and about 500 ml of distilled water to a one liter volumetric flask. Add 1.88 grams of dry, reagent-grade NaCN and swirl the flask gently to dissolve the solid. Dilute to the mark with distilled water, cap, and upend the flask several times to thoroughly mix the contents. Store all standards in plastic bottles and prepare weekly. 4. GENERAL PREPARATION Electrode Preparation Remove the rubber caps covering the electrode tips and the rubber insert covering the filling hole of the cyanide 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 100 ml of distilled water and 1 ml of 10M NaOH 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. Using a pipet, add 1 ml of 1.0X10-2M or 1,000 ppm standard to the beaker. When the reading is stable, record the mV reading. Using a pipet, add 10 ml of the same standard used above to the beaker. After the reading has stabilized, record the mV reading. The electrode is operating correctly if the mV potential has changed by 57±2 mV, assuming the solution temperature is between 20o and 25oC. See the TROUBLESHOOTING sections if the potential change is not within this range. 2. 3. 4. Slope is defined as the change in potential observed when the concentration changes by a factor of 10. Electrode Slope Check (with an ion meter) (Check electrodes each day) 4 Instruction Manual Cyanide Electrode 1. Prepare standard cyanide solutions whose concentrations vary by tenfold. Use either the 1.0X10-2M or the 1,000 ppm cyanide standard. Use the serial dilution method for this preparation. To a 150 ml beaker, add 100 ml of the lower value standard and 1 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. Adjust the meter to the concentration of the standard and fix the value in the memory according to the meter manufacturer's instructions. Rinse the electrodes with distilled water and blot dry. To a 150 ml beaker, add 100 ml of the higher value standard and 1 ml of ISA. Place the beaker on a magnetic stirrer and begin stirring at a constant rate. Lower the electrode tips into the solution. Adjust the meter to the concentration of the standard and fix the value in the memory. Read the electrode slope according to the meter manufacturer's instructions. Correct electrode operation is indicated by a slope of 93-100%. See TROUBLESHOOTING section if the slope is not within this range. 2. 3. 4. 5. 6. 7. 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 about a 2% 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 insulating material, such as styrofoam sheet, between the stirrer and the beaker. Always rinse the electrodes with distilled water and blot dry between measurements. Use a clean, dry tissue to prevent cross contamination. When making low level measurements (below 1X10-5M), use only plastic lab-ware and cover the beaker with Parafilm to avoid loss of cyanide. When making high cyanide measurements (above 1X10-3M), samples should be diluted before measurements. Use fresh standards for calibration. Use 1 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 5 Cyanide Electrode Instruction Manual 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 epoxy body electrode. Please check with Eutech Instruments Pte Ltd. before using the electrode in other solvents. The temperature of the sample solutions and of the standard solutions should be the same and below 80oC. Interferences should be absent. If they are present, use the procedure ...