15
Saving Confirmation
Enable this option to force confirmation of a change made to a
setting in GLP data option field or a Sample ID name. If Saving
Confirmation is enabled, the user will have to accept the change
with a key stroke. If Saving Confirmation is disabled, the changes
made to these fields change automatically without asking for
confirmation.
GLP Data
Use this option to customize logging GLP information with specific identification data. When enabled, these ID
tags will be included in the GLP section of all data logs for all modes of operation and both channels (
HI 5222
).
Each data field can use up to 10 characters.
The five available fields are:
Operator ID
: used to add the name of the operator
Instrument ID
: used to name an instrument with a discrete name, location or number
Company Name
: used to include the Company ID to the GLP data field.
Additional Info
: Two data fields are available for general notes or notations.
66
The Nernst equation can be rewritten:
ION SELECTIVE ANALYSIS METHODS
Direct Analysis
This method is a simple procedure for measuring multiple samples. It should only be used in the linear
working regions of the sensor. A direct reading instrument such as the
HI 5222
determines concentration of
the unknown by a direct reading after calibrating the instrument with the standards. The instrument is
calibrated as described in “ISE CALIBRATION & MEASUREMENTS” section, with two or more freshly made
standards that are in the measurement range of the unknowns. Ionic strength adjustment is made to samples
and standards. Unknowns are measured directly by the instrument.
At lower concentrations, in non-linear regions of the electrode response, multiple calibration points will extend
measurements to a practical detection limit. Calibrations must be performed more frequently in these cases.
Incremental Methods
Incremental methods are useful for the measurement of samples whose constituents are variable or
concentrated. Incremental techniques can reduce errors from such variables as temperature, viscosity, or pH
extremes and will provide indirect analysis of ions for which there is no ISE sensor for a direct measurement.
There are four commonly used different incremental methods for sample measurement. They are Known
Addition, Known Subtraction, Analyte Addition and Analyte Subtraction.
HI 5222
allows the analyst to use
these techniques as a simple routine procedure, thus eliminating calculations or tables. The method once set
up can be used for repetitive measurements on multiple samples.
Known Addition and Known Subtraction
With Known addition,
standard is added
to a sample being measured. The standard and sample contain the
same Ion. mV are taken before and after the standard addition. From the change in mV, the sample
concentration is determined.
With Known subtraction,
a known standard is added to an ionic sample
being measured. The standard reacts
with the measured Ion in the sample in a known manner, thus removing measured ions from the solution.
From the change in mV, the concentration of the sample is determined.
E
=
E
o
+
S
log(
C
)
C
SAMP
=
C
STD
·
V
STD
·
f
·
(
V
SAMP
+
V
ISA
)
(
V
SAMP
+
V
ISA
)
- (
V
SAMP
+
V
STD
+
V
ISA
)·10
∆
E
V
SAMP
S
C
SAMP
=
C
SAMP
·
V
STD
·
(
V
SAMP
+
V
ISA
)
(
V
SAMP
+
V
STD
+
V
ISA
)·10
∆
E
- (
V
SAMP
+
V
ISA
)
V
SAMP
S
