1-8
given in your instrument manual. Check glassware used in the
procedure, making sure that it is scrupulously clean. Dirty pipets and
graduated cylinders are sources of contamination and will not deliver the
correct volumes. Hach's TenSette Pipet for dispensing Standards and
standards sealed in Voluette Ampules are ideal for standard additions.
If a defect is found in the instrument and/or apparatus, repeat Branch B
after repair or replacement of the instrument and/or apparatus. If the
instrument and apparatus are found to be in good working order, proceed
with Branch I.
Branch I
After determining the procedure, reagents, instrument and/or apparatus
are correct and operating properly, an analyst may conclude the only
possible cause for standard additions not functioning properly in
deionized water is the set of standards used in performing the standard
additions. Obtain a new set of standards and repeat Branch B.
Branch F
Examples of non uniform increments between standard additions are
shown below.
Example A:
mL Std. mg/L Std. mg/L
Added Added Found
00 1.0
0.1 0.2 1.10
0.2 0.4 1.18
0.3 0.6 1.23
Example B:
mL Std. mg/L Std. mg/L
Added Added Found
00 0
0.1 0.2 0
0.2 0.4 0.2
0.3 0.6 0.4
The two examples illustrate the effect of interferences on the standard
addition and on substances in the sample. Data plotted on the Figure 2
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