Incremental
Techniques
|
Section 6
Electrode ID and Slope for Incremental
Techniques
The meter uses the electrode ID to determine the valence of the ion of interest and the
theoretical slope of the electrode. The following table shows the electrode ID options and their
corresponding valence and theoretical slope values.
Electrode ID
Valence
Number
Theoretical
Slope
Electrode ID
Valence
Number
Theoretical
Slope
pH
+1
+59.16
Calcium
(Ca
+2
)
+2
+29.58
Fluoride
(F
-
)
-1
-59.16
Silver
(Ag
+
)
+1
+59.16
Ammonia
(NH
3
)
-1
-59.16
Copper
(Cu
+2
)
+2
+29.58
Ammonium
(NH
4+
)
+1
+59.16
Lead
(Pb
+2
)
+2
+29.58
Nitrate
(NO
3-
)
-1
-59.16
Cadmium
(Cd
+2
)
+2
+29.58
Nitrite
(NO
2-
)
-1
-59.16
Perchlorate
(ClO
4-
)
-1
-59.16
Sulfide
(S
-2
)
-2
-29.58
Fluoroborate
(BF
4
¯)
-1
-59.16
Chloride
(Cl
-
)
-1
-59.16
Thiocyanate
(SCN
-
)
-1
-59.16
Chlorine
(Cl
2
)
+2
+29.58
Nitrogen
Oxide (NO
X
)
+1
+59.16
Bromide
(Br
-
)
-1
-59.16
Carbon
Dioxide (CO
2
)
+1
+59.16
Iodide
(I
-
)
-1
-59.16
Monovalent
Cation (X
+
)
+1
+59.16
Cyanide
(CN
-
)
-1
-59.16
Divalent
Cation (X
+2
)
+2
+29.58
Sodium
(Na
+
)
+1
+59.16
Monovalent
Anion (X
-
)
-1
-59.16
Potassium
(K
+
)
+1
+59.16
Divalent Anion
(X
-2
)
-2
-29.58
Thermo Scientific
Orion Dual Star pH/ISE Benchtop Meter User Manual
|
51
Section 6
|
Incremental Techniques
Single Known Addition
A standard of known concentration is added to a sample of unknown concentration. The total
concentration should approximately double upon the addition of the standard, therefore sample
concentration should be known within an order of magnitude. Refer to the following table to
choose the correct standard concentration and volume of addition.
Amount of standard to be added
per 100 mL of sample
Standard concentration compared to expected sample concentration
1 mL
100 times more concentrated
5 mL
20
times more concentrated
10 mL
10 times more concentrated
•
Refer to the appropriate electrode user guide for instructions for preparing the
electrode,
required solutions (ionic strength adjusters, standards, etc) and any special requirements.
Determine the electrode slope as directed in the electrode user guide.
•
Ensure that the electrode, ATC probe and reference electrode (if applicable) are connected
to the meter inputs that correspond with the selected channel.
Single Known Addition Procedure
1. Prepare the sample as directed in the electrode user guide.
2. In the measurement mode, press the setup key. Press the ▲ / ▼ keys to highlight
Incremental Techniques and press the f2 (select) key.
3. Dual channel display only: Press the ▲ / ▼ keys to select the channel to perform the single
known addition on and press the f2 (accept) key.
4. Press the ▲ / ▼ keys to highlight Single Known Addition and press the f2 (select) key.
5. Use the numeric keypad, decimal key and +/- key to enter the electrode slope and press the
f2 (accept) key. Determine the electrode slope as directed in the electrode user guide or use
the theoretical slope from the
Electrode ID and Slope for Incremental Techniques
section.
6. Use the numeric keypad and decimal key to enter the sample volume, in mL, and press the
f2 (accept) key.
7. Use the numeric keypad and decimal key to enter the total volume, in mL, and press the
f2 (accept) key. The total volume includes the sample volume, ISA volume and diluting
agent volume, but not the standard volume.
8. Use the numeric keypad and decimal key to enter the concentration of the standard and
press the f2 (accept) key.
52
|
Orion Dual Star pH/ISE Benchtop
Meter User Manual
Thermo Scientific