Instruction Manual Bromide Electrode EUTECH INSTRUMENTS PTE LTD.
Instruction Manual Bromide Electrode TABLE OF CONTENTS GENERAL INSTRUCTIONS .......................................................................................................... 1 Introduction.................................................................................................................................................3 Required Solutions......................................................................................................................................
Instruction Manual Bromide Electrode EUTECH INSTRUMENTS PTE LTD. BROMIDE ION ELECTRODE INSTRUCTION MANUAL GENERAL INSTRUCTIONS Introduction Eutech Instruments Bromide Electrode is used to measure free bromide ion 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.
Instruction Manual Bromide Electrode GENERAL PREPARATION Electrode Preparation Remove the rubber caps covering the electrode tips and the rubber insert covering the filling hole of the combination electrode or of 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.
Instruction Manual 5. 6. 7. Bromide Electrode 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. 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 90-100%.
Instruction Manual Bromide Electrode Units of Measurement Bromide ions can be measured in units of moles/liter, parts/million, or any other convenient concentration unit. Table 1 indicates some of the concentration units. TABLE 1: Concentration Unit Conversion Factors moles/liter 1.0X10-4 1.0X10-3 1.0X10-2 1.0X10-1 ppm Br-1 8.0 79.9 799.0 7,990.0 MEASUREMENT PROCEDURE Direct Measurement Direct measurement is a simple procedure for measuring a large number of samples.
Instruction Manual Bromide Electrode A calibration curve is constructed on semi-logarithmic paper when using a pH/mV meter in the millivolt mode. The measured electrode potential in mV (linear axis) is plotted against the standard concentration (log axis). In the linear region of the curve, only three standards are necessary to determine a calibration curve. In the non-linear region, additional points must be measured. The direct measurement procedures given are for the linear portion of the curve.
Instruction Manual 2. 3. Bromide Electrode Place the more dilute solution on the magnetic stirrer and begin stirring at a constant rate. Assure that the meter is in the concentration mode. Lower the electrode tips into the solution. Adjust the meter to the concentration of the standard and fix the value in the memory according to the meter manufacturer's instructions after stabilization of the reading. 4. Rinse the electrodes with distilled water and blot dry. 5.
Instruction Manual Bromide Electrode 4. Place the rinsed, dried electrode tips in the solution and assure that the meter is in the mV mode. 5. Add increments of the 1.0X10-4M or 10 ppm standard as given in Table 2 below. 6. After the reading has stabilized, record the mV reading after each addition. Electrode response time is much longer at these levels. Allow adequate time for the electrodes to stabilize.
Instruction Manual Bromide Electrode Interferences A layer of silver may form on the electrode surface in the presence of strong reducing agents. Insoluble salts of silver may be deposited on the membrane, causing electrode malfunction if high levels of ions forming these salts are present in the sample. Proper performance can be restored by polishing. See the section Electrode Response for proper polishing procedure.
Instruction Manual Bromide Electrode Complexation Total concentration (Ct) consists of free ions (Cf) and complexed or bound ions (Cc) in solutions: Ct = Cf + Cc Since the electrode only responds to free ions, any complexing agent in the solution reduces the measured concentration of ions. Bromide ions complex with some metal ions. Table 4 lists the levels of complexing metals causing a 20% error at 1.0X10-4M bromide. TABLE 4: Levels of Complexing Agents Causing a 20% Error at 1.
Instruction Manual Bromide Electrode If the temperature varies substantially from room temperature, equilibrium times up to one hour are recommended. Electrode Response Plotting the electrode mV potential against the bromide concentration on semi-logarithmic paper results in a straight line with a slope of about 57 mV per decade. (Refer to Figure 1.
Instruction Manual Bromide Electrode Limits of Detection The upper limit of detection in pure sodium bromide solutions is 1M. In the presence of other ions, the upper limit of detection is above 1.0x10-1M bromide, but the possibility of a liquid junction potential developing at the reference electrode and the "salt extraction effect" are two limiting factors. Some salts may infuse into the electrode membrane at high salt concentrations, causing deviation from the theoretical response.
Instruction Manual Bromide Electrode X = level of bromide ions in solution The activity, X, represents the effective concentration of the ions in solution.
Instruction Manual Bromide Electrode TROUBLESHOOTING GUIDE The goal of troubleshooting is the isolation of a problem through checking each of the system components in turn: the meter, the glass-ware, the electrodes, the standards and reagents, the sample, and the technique. Meter The meter may be checked by following the check-out procedure in instrument instruction manual. Glass-ware Clean glass-ware is essential for good measurement.
Instruction Manual Bromide Electrode Try to determine the composition of the samples prior to testing to eliminate a problem before it starts. (See Measuring Hints, Sample Requirements, and Interferences.) Technique Be sure that the electrode's limit of detection has not been exceeded. Be sure that the analysis method is clearly understood and is compatible with the sample. Refer to the instruction manual again. Reread sections on GENERAL PREPARATION and ELECTRODE CHARACTERISTICS.
Instruction Manual Bromide Electrode TROUBLESHOOTING HINTS Symptom Out of Range Reading Noisy or Unstable Readings (readings continuously or rapidly changing) Drift (reading slowly changing one direction) Possible Causes defective meter Next Step check meter with shorting strap (see meter instruction manual) defective electrode check electrode operation electrodes not plugged in properly unplug electrodes and reset reference electrode not filled be sure reference electrode is filled air bubble
Instruction Manual Low Slope or No Slope "Incorrect Answer" (but calibration curve is good) Bromide Electrode standards contaminated or incorrectly made prepare fresh standards ISA not used use recommended ISA standard used as ISA use ISA electrode exposed to complexing agents check section entitled air bubble on membrane remove bubble by re-dipping probe incorrect scaling of semi-log paper plot millivolts on the linear axis.
Instruction Manual Bromide Electrode SPECIFICATIONS Concentration Range: 1M to 5 x 10-6M 79,900 ppm to 0.4 ppm pH Range: 2-14 Temperature Range: 0o to 80°C Resistance: <1 Mohm Reproducibility: ±2% Samples: Aqueous solutions only; avoid organic solvents Size: 110 mm in length; 12 mm in diameter; 1 m cable length Storage: Store in bromide solution ORDERING INFORMATION CODE/NO. DESCRIPTION EC-BRO-03 Bromide Ion Combination Electrode, epoxy body EC-SCS-BR1-BT Bromide Standard, 0.
