Hach DR2400, Manual

Page: 44 / 66

Standard Additions
Standard Additions
Page 44
5940018StdAdd.fm
6.2 Using the Standard Additions Option
Standard additions involves adding small volumes of a known standard to a
specific volume of sample. This “spiked” sample is then analyzed for the
additional standard. The process includes three important items: (1) standard
concentration; (2) standard additions volumes; and (3) sample volume.
The sample volume is not necessarily the volume analyzed in the procedure; it is
the original volume of sample to which the standard is added. For example, in
Hach Program 320, standard is added to 30 mL of sample, but only 10 mL of the
solution is actually analyzed in the procedure. It is important to note that the
volume of sample tested in the method does not change.
Not all Hach Programs include the Standard Additions option.
Hach Programs that have the Standard Additions option are usually
pre-programmed for the three items listed above. These values are the same as
those outlined in the
Accuracy Check instructions at the back of the procedure.
For alternative spiking schemes, the default values can be overridden. The
values entered into the DR/2400, however, must be the same as those used to
spike the samples.
Note: Standard additions uses the units and chemical form currently in effect. Make certain that
subsequent entries are made in the correct units.
Select a measurement mode from the Main Menu. Modes with the Standard
Additions option include most Hach programs and user programs that are
derived from Hach programs.
Example: (using Hach Program 10)
1. From the Main Menu, touch
Hach Programs
. Touch
Select by Number
and
enter
10
. Touch
OK
. Touch
Start Program
.
2. Analyze an unspiked sample per the instructions in the Procedures Manual .
Leave the sample in the cell holder after taking a reading.
3.
From the Hach Programs menu, touch
Options
, then
Standard
Additions
. A summary of the standard additions procedure
will appear.
4. Touch
OK
to accept the default values for standard
concentration, sample volume, and spike volumes. Touch
Edit
to
change these values. After values are accepted, the unspiked
sample reading will appear in the top row.