3.21 MULTIPLE SAMPLE ADDITION/SUBTRACTION
This menu option will begin a sample addition measurement. The sample concentration is initially calculated
using:
Where:
Cu
=
Sample concentration
Cs
=
Standard concentration
Vs
=
Volume of standard
Vu
=
Volume of sample
E
=
Change in electrode potential
S
=
Slope of electrode
If a subsequent sample is added to perform a multiple sample addition measurement, then the sample con-
centration is recalculated using the above expression but with the cumulative standard volume and the nth
sample volume. The standard concentration is found using:
Where:
Cm
=
Concentration of mixture
Cs
=
Concentration of standard
Vs
=
Volume of standard
Cu
=
Concentration of previous sample
Vu
=
Volume of previous sample
To perform a measurement the following procedure should be carried out::
Select SAMPLE± mode using the arrow keys and pressing . Enter the SETUP... menu using the
arrow key and pressing . This menu option gives access to the parameters relating specifically to
a sample addition or subtraction measurement.
Select NUMBER OF SAMPLES using the arrow key. Press . Enter the number of samples using
the numeric keys and press . It is recommended that for optimum accuracy of readings only four samples
be measured at one time.
Cu =
Cs. (Vu + Vs). (10
ES
- Vs / (Vs + Vu)
Vu
Cm
=
Cs. Vs + Cu. Vu
Vs + Vu
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