eutech-instruments bromide epoxy Manual Do Utilizador
Instruction Manual
Bromide Electrode
9
4.
Place the rinsed, dried electrode tips in the solution and assure that the meter is in the mV
mode.
mode.
5.
Add increments of the 1.0X10
-4
M 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.
response time is much longer at these levels. Allow adequate time for the electrodes to
stabilize.
TABLE 2: Step-wise Calibration for Low Level Bromide Measurements
Added
Concentration
Step
Pipet Volume (ml)
M
ppm
1
A
0.1
1.0X10
-7
0.01
2
A
0.1
2.0X10
-7
0.02
3
A
0.2
4.0X10
-7
0.04
4
A
0.2
6.0X10
-7
0.06
5
A
0.4
9.9X10
-7
0.99
6
B
2.0
2.9X10
-6
2.90
7
B
2.0
4.8X10
-6
4.80
Pipet A = 1 ml graduated pipet
Pipet B = 2 ml pipet
Solutions: additions of 1.0X10
-4
M or 10 ppm standard to 100 ml of solution
as prepared in Step 3 above.
7.
On a semi-logarithmic graph paper, plot the mV reading (linear axis) against the
concentration (log axis) as in Figure 1.
concentration (log axis) as in Figure 1.
8.
Rinse the electrodes in distilled water and blot dry.
9.
Measure out 100 ml of sample into a 150 ml beaker, add 1 ml of low level ISA. Place the
beaker on the magnetic stirrer and begin stirring at a constant rate. Lower the electrode tips
into the solution. After the reading has stabilized, record the mV reading and determine the
concentration from the low level calibration curve.
beaker on the magnetic stirrer and begin stirring at a constant rate. Lower the electrode tips
into the solution. After the reading has stabilized, record the mV reading and determine the
concentration from the low level calibration curve.
10. Prepare a new low level calibration curve daily. Check the calibration curve every 1-2
hours by repeating Steps 2-7 above.
ELECTRODE CHARACTERISTICS
Reproducibility
Electrode measurements reproducible to ±2% can be obtained if the electrode is calibrated every
hour. Factors like temperature fluctuations, drift, and noise limit reproducibility. Reproducibility is
independent of concentration within the electrode's operating range.