d. Example 4. Determine the amount of serum in 40 mL of a 1:5 dilution of
serum with saline.
Solution. Read the problem carefully and use ratio and proportion to
determine the amount of serum in the given volume of solution.
1 part serum
x mL serum
------------ ------------
5 total parts
40 mL total
(5 total parts) (x mL serum) = (40 mL total)(1 part serum)
40 mL total)(1 part serum)
------------------------= x mL serum
5 total parts
x mL serum = 8 mL serum
6-3.
SERIAL DILUTIONS
Serial dilution techniques are used when it is necessary to test several
successive dilutions on the same sample. The procedure involves the preparation of an
initial dilution and subsequent redilution of aliquots (portions) to give progressively more
dilute solutions. In order to calculate the final or intermediate dilutions, use each dilution
of interest as a multiplicative factor, of which the resulting product is the dilution.
a. Example 1. A serum specimen was successively diluted 1:2, 1:2, and 1:2
with saline. What is the final dilution of the specimen?
Solution. When determining the final dilution of a series of dilutions use each
dilution as a multiplicative factor. The resulting product is the final dilution.
1
1
1
1
-- X -- X -- = -- or equivalently, 1:8
2
2
2
8
b. Example 2. A 1:10 dilution of a substance is rediluted 3:5, 2:15, and 1:2.
What is the final dilution?
MD0837
6-4