16
To add the GLP Data:
• Press
while in
Measure
mode.
• Press
.
• Use
or
to select the GLP Data option.
• Press
and use
or
to highlight the
desired option.
• Press
to edit the desired information. The Text Editor
menu will be displayed on the LCD.
• Enter the desired information by accepting the highlighted
character which is added to the text bar, using
. The
and
keys help the user to select the desired character. It is also possible to delete the last
character by positioning the cursor on the Backspace character ( ) and pressing
.
• Press
to return to the GLP Data options. If the Saving Confirmation is enabled, press
to
accept the modified option,
to escape without saving or
to return to the editing mode.
Otherwise, the modified options are saved automatically.
Date & Time
Set the current date & time and the format in which they appear.
Set Date and Time
This option allows you to set the current date (year/month/day) and time (hour/minute/second).
Notes:
• Only years starting with 2000 are accepted.
• The time is set using the selected time format. For 12 Hour time format only, the AM/PM can
also be selected with
or
.
Set Time Format
Choose between 12-Hour (AM/PM) time format or 24-Hour time format.
Set Date Format
Choose the desired date format from 7 available options: DD/MM/YYYY, MM/DD/YYYY, YYYY/MM/DD, YYYY-MM-DD,
Mon DD, YYYY, DD-Mon-YYYY or YYYY-Mon-DD.
To set the Date & Time:
• Press
while in
Measure
mode.
• Press
.
65
ADDITIONAL INFORMATION
ISE THEORY
An Ion Selective Electrode (ISE) is an electrochemical sensor that changes voltage with the activity or concentration
of ions in solutions. The change in voltage is a logarithmic relationship with concentration, and is expressed by
the Nernst equation:
where:
E
- the measured voltage;
E
o
- standard voltage and other standard system voltages;
a
- the activity of the Ion being measured;
S
- the Nernst slope factor and is derived from thermodynamic principles:
R
- the universal gas constant (8.314 J/Kmol);
T
- the temperature in degrees Kelvin;
F
- the Faraday’s constant (96,485 C/mol);
n
- the Ion charge.
The slope may be positive or negative depending upon the Ion charge (n).
Activity and concentration are related by an “activity coefficient”, expressed as:
where:
a
- the activity of the Ion being measured;
γ
- the activity coefficient;
C
- the concentration of the Ion being measured.
In very dilute solutions
γ
approaches 1 so activity and concentration are the same.
Actual samples that are more concentrated have much smaller activity coefficients (
γ
< 1). The addition of an
inert background salt to standards and samples stabilizes the activity coefficient so that concentration measurements
may be made directly. Some of Hanna’s Ionic Strength Adjuster formulations also may optimize pH and complex
interferences, in addition to standardizing the ionic strength.
S
E
I
C
E
P
S
E
P
O
L
S
)
e
d
a
c
e
d
/
V
m
(
n
o
it
a
c
t
n
e
l
a
v
o
n
o
M
6
1
.
9
5
+
n
o
i
n
a
t
n
e
l
a
v
o
n
o
M
6
1
.
9
5
–
n
o
it
a
c
t
n
e
l
a
vi
D
8
5
.
9
2
+
n
o
i
n
a
t
n
e
l
a
vi
D
8
5
.
9
2
–
E
=
E
o
+
S
log(
a
)
S
=
2.303
RT
nF
a
=
γ
·
C
