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60
• When the reading is stable, press
to store the second mV reading. The ISE measurement
results will be displayed on the LCD.
• Press
to log the current results into an ISE Method Report. Press to return to
ISE Measure mode. Press
to start another measurement. Rinse ISE sensor between
samples.
• Press
, to modify parameters.
Note: Press
at any time to stop the measurement and return to ISE Measure mode.
ANALYTE ADDITION
To measure the concentration of a sample using Analyte Addition method:
• Press
and then to select ISE Measure mode for the selected channel.
• Select the Analyte Addition method (see ISE Setup
→ Reading Mode).
• Prior to starting an AA procedure, the ISE sensor must be calibrated with a minimum of two
standards containing ISA. The slope of the electrode will be used in all calculations involved in
AA.
• If following an established procedure: Press
then edit the method variables and follow
the procedure below.
• Press
to set the method parameters. Press / to select next/previ-
ous parameter to edit, then press and use or to set the desired
parameter value. Press to save the modified value and then press to exit
method parameters edit menu.
• If developing a procedure: Before attempting Analyte Addition analysis, it is important to
determine which standard volume, concentration and sample size will produce the best results.
As a general rule, the standard must be less concentrated than the sample so the addition of
sample will increase the total ion content of the solution from the beaker and change the mV
value by at least 10 mV. For a positively charged ion (i.e. Sodium), the AA increases the mV.
For a negatively charged ion (i.e. Sulfide, Fluoride, Chloride), the AA should decrease the mV.
Start with a small trial. For example: Measure 50 mL of standard, add a magnetic stir bar and
place on a stirrer, add ISA (consult ISE manual) and place ISE electrode tip into the sample. Put
instrument in mV mode and record the observed mV. Using a micropipette, add a volume of the
sample. Start by adding 500 µL at a time (for example). Watch the change in mV. When you
have observed approximately a 10 mV change from the original standard, calculate the total
volume added. Adjust sample and standard volumes proportionally to standard volumes that
can be measured with accuracy. Use volumetric pipettes for standard, ISA and sample addition.
ISE MEASUREMENT (HI5222 only)
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