3 matrix correction – manual, Matrix correction – manual, Operation – Hach-Lange NISE sc User Manual
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Operation
The matrix correction process requires operating steps to be completed on the sc
controller and on a LINK2SC-compatible photometer.
Refer to the LINK2SC user manual for a detailed description of the LINK2SC procedure.
When using the LINK2SC software, sections
are not relevant.
4.6.3 Matrix correction – manual
ISE probes offer different options (refer to
Table 1
) for correcting the sensor value with
laboratory values (as a reference value).
The laboratory value of the water sample is entered as nitrate nitrogen (NO
3
–N) and/or as
ammoniacal nitrogen (NH
4
–N). This laboratory value replaces the prior value measured
by the sensor.
Table 1 Correction options for ISE probes
Correction option
Application
MATRIX 1
VALUE CORR. 1
VALUE CORR. 2
MATRIX 2
HIST. CORR.
A MATRIX 1 is the most commonly used correction option and performs a 1 point matrix
correction for ammonium and/or nitrate (
). It is advisable to perform a MATRIX1 as
the first correction. The Matrix1 correction can be performed both with and without correction of the
compensation electrodes (potassium or chloride); in most cases, it is sufficient to perform it without
correction. A correction featuring potassium and/or chloride is only necessary if a high level of
accuracy is required. With a MATRIX1, a sample must be taken when the correction is triggered and
analyzed in the laboratory. The MATRIX1 is activated when the laboratory value is entered.
Value correction 1 (correction at one concentration point) corresponds to a MATRIX1 correction
with an alternative entry format.
Comparison values between the ISE probe and the laboratory can be collected over a period of
around a week with this correction. The correction can be performed at a later stage.
Value correction 2 (correction at 2 different concentration points) should be performed if dynamic
concentration fluctuations are present over at least half a decade
1
and a MATRIX1 or VALUE
CORR. 1 does not achieve a sufficiently accurate result.
Comparison values between the ISE probe and the laboratory can be collected over a period of
around a week with this correction. The correction can be performed at a later stage.
The MATRIX 2 correction corresponds to a VALUE CORR. 2, but uses an alternative entry
format and is recommended if there is a dynamic process with a large nitrate/ammonium fluctuation
greater than at least half a decade
1
. With a MATRIX2, a sample must be taken for both points when
the correction is triggered and analyzed in the laboratory. The MATRIX2 is activated when the
laboratory value is entered.
Return to one of the last matrix and value corrections performed if a correction has not produced
a successful result.
1
Examples of half a decade: The concentration of nitrogen nitrate shifts between 1 and 5 mg NO
3
–N or
between 5 and 25 mg/L NO
3
–N. (conc2 = (conc1 x 10)/2)