• Two-fold serial dilutions A two-fold dilution reduces the concentration of a solution by a factor of two that is reduces the original concentration by one half. A series of two-fold dilutions is described as two-fold serial dilutions.
• Serial dilutions are made by making the same dilution step over and over, using the previous dilution as the input to the next dilution in each step. Since the dilution-fold is the same in each step, the dilutions are a geometric series (constant ratio between any adjacent dilutions).
• The first step in making a serial dilution is to take a known volume (usually 1ml) of stock and place it into a known volume of distilled water (usually 9ml). This produces 10ml of the dilute solution. This dilute solution has 1ml of extract /10ml, producing a 10-fold dilution.
• 2-fold dilution is a bit confusing, a better way of describing dilution is ratio. For example, 2 fold dilution equals to 1:2 dilution. Since you mentioned serial dilution, you do this by first mixing an equal volume of bacteria and water (whatever used for dilution), and then mix an equal volume of the first mixture and water.

• 2 Fold Dilution Example
• Two Fold Serial Dilution Method
• 4 Fold Serial Dilution
• Serial Dilution Steps
• 5 Fold Serial Dilution
• 3 Fold Serial Dilution Chart

A dilution is a reduction in the concentration of a solution. A serial dilution is a series of repeated dilutions that provides a geometric dilution of the original solution. This is commonly performed in experiments that involve concentration curves on a logarithmic scale. Serial dilutions are used extensively in biochemistry and microbiology.

1 Answer

Answer:

You could do the dilutions in one step, or you might have to do serial dilutions.

Explanation:

There is a limit to how much you can dilute a sample in one step.

You probably wouldn't want to dilute by more than a factor of 100 in a single step, because that would give you a large volume of dilute solution.

Rather, you would use the serial dilution technique.

Remember the formula for dilution factor (#'DF'#):

#'DF' = V_f/V_i#, where

#V_i = 'aliquot volume'# and

#V_f = 'final volume' = 'aliquot volume + diluent volume'#

(a)#'DF' = 50#

Here we can do a single dilution.

We can add 0.2 mL of sample to 9.8 mL of diluent (normal saline? cells will burst in distilled water because of osmotic pressure).

#V_f = '0.2 mL + 9.8 mL' = '10.0 mL'#

#'DF' = V_f/V_i = (10.0 cancel('mL'))/(0.2 cancel('mL')) = 50#

(b)#'DF' = 100#

Here, too, we can do a single dilution.

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This time we add 0.1 mL of sample to 9.9 mL of saline.

#V_f = '0.1 mL + 9.9 mL' = '10.0 mL'#

#'DF' = V_f/V_i = (10.0 cancel('mL'))/(0.1 cancel('mL')) = 100#

(c)#'DF' = 200#

Here you might want to do a serial dilution.

The formula for serial dilutions is

#'DF' = 'DF'_1 × 'DF'_2 × 'DF'_3 ×…#

How about a 1:100 dilution followed by a 1:2 dilution?

(1) Add 0.1 mL of sample to 9.9 mL of diluent. #'DF'_1 = 100#. Call this 'Solution 1'.

(2) Add 5 mL of Solution 1 to 5 mL of saline. Call this 'Solution 2'.

2 Fold Dilution Example

#V_i = '5 mL'#

#V_f = '5 mL + 5 mL' = '10 mL'#

Two Fold Serial Dilution Method

#'DF'_2 = V_f/V_i = (10 cancel('mL'))/(5 cancel('mL')) = 2#

4 Fold Serial Dilution

#'DF' = 'DF'_1 × 'DF'_2 = 100 × 2 = 200#

Serial Dilution Steps

5 Fold Serial Dilution

3 Fold Serial Dilution Chart