1-25
The concentration of the sample is equal to the diluted sample reading
times the multiplication factor.
An example: A 2.5 mL sample was diluted with 22.5 mL of deionized
water. The result was 0.35 mg/L. What is the concentration of the sample?
0.35 x 10 = 3.5 mg/L
More accurate dilutions can be done with a pipet and a 100-mL
volumetric flask. Pipet the sample and dilute to volume with deionized
water. Invert several times to mix.
Table 6. Multiplication factors to be used when sample is diluted
to 100 mL
Sample Volume (mL) Multiplication Factor
1100
250
520
10 10
25 4
50 2
Sample dilution also influences the level at which a substance may
interfere. The effect of the interferences decreases as the sample size
decreases. Therefore, the effect of the interference described in the
procedure notes will decrease as the sample size decreases. In other
words, higher levels of an interfering substance can be present if the
sample is diluted.
An example: Copper does not interfere at or below 100 mg/L for a
25.00 mL sample in a procedure. If the sample volume is diluted with an
equal volume of water, what is the level at which copper will not interfere?
The level at which copper will not interfere in the sample is at or below
200 mg/L.
Total Volume
Sample Volume
= Dilution Factor
25
12.5
= 2
Interference
level
x
Dilution
factor
=
Interference level
in sample
100 x 2 = 200 mg/L
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