Basic Laboratory Techniques Dilutions Biology Essay

Dilution is a procedure of doing a weaker or a less concentrated solution. Substances which are extremely concentrated can be debatable to transport out trials. For case, when a blood sample is placed on a slide it would be hard to number cells due to overlapping. As a consequence dilutions are carried out so that the cells will be more dispersed. Furthermore a big sum of reagent would be needed to respond with a extremely concentrated substance. This is unequal since big sums of reagent would be wasted. In add-on it is impractical to utilize big volumes of substances illustration buffers. By and large a concentrated signifier is present and so the necessary dilutions are made for different trials. A manual of how the dilutions are made is typically present with the reagent.

Adequate setup must be used for dilutions. Basically, there are two types of dilutions. One, where the concluding particular concentration merely is important and the other where both the concluding volume and concentration are important.

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Dilution symbols are important.

1/10 refers to 1ml sample with 9mls dilutants for a entire volume of 10mls. This is the same as 1+9.

1:10 refers to 1ml sample with 10mls dilutants for a entire volume of 11mls. This is the same as 1+10.

Consecutive dilution is a method used to thin a substance into solution stepwise with a changeless dilution factor in each measure. The dilution factor is the volume of stock / entire volume. The first measure in doing a consecutive dilution is to take a known volume ( illustration 1ml ) of stock i.e. the original sample and topographic point it into a known volume of H2O ( illustration 9ml ) . This produces 10ml of dilute solution. The dilute solution has 1ml of original sample / 10ml. The technique used to do a individual dilution is repeated utilizing the old dilute solution. At each measure, 1ml of the old dilution is added to 9ml of distilled H2O. This is repeated consecutive until the needed dilution is achieved. The volumes of substances used vary consequently. During dilutions it is indispensable to pipette the larger volume foremost and so the smaller volume.

Diagram of how consecutive dilutions are made:

Rule: Original concentration = New concentration

Dilution factor

Since the dilution-fold is the same in each measure, the dilutions are a geometric series i.e a changeless ratio. Example: 1/3, 1/9, 1/27, 1/81. Each dilution is a treble. A double and a quintuple besides exist where it is multiplied by 1/2 and 1/5 severally.

Consecutive dilutions are chief for several state of affairss. In the lab there are a figure of volumetric flasks nevertheless there is non a batch of 1000ml flasks. Hence consecutive dilutions are the lone manner to acquire the coveted concentration. Consecutive dilutions are basically used for standardization curves to guarantee the truth of the measurings. This is utile since if a minor error is done, it is non noticed since the error will be repeated in all the dilutions and as a consequence there will be no consequence. Furthermore consecutive dilutions are used for antibody titers. A trial can be quantitative illustration the concentration of glucose in blood is 6 or qualitative if the trial is positive or negative illustration when proving for the human immunodeficiency virus if it is present in the blood sample, the consequence is either positive or negative. However there is another trial known as the semi-quantitative trial where the consequence is neither numerical nor positive or negative. When consecutive dilutions are carried out, the consequence can be that the antibody titer is positive up to 1/320. It shows that the patient is immune up to a certain bound. This is frequently used to supervise intervention.


Exercise 1:

Perform and happen out the dilution of the followers:


Mix 25µl of B with 75µl of H2O

Dilution = 1:3, 1/4

Mix 20µl of B with 780µl if H2O

Dilution = 1:39, 1/40

10µl of B with 190µl of H2O

Dilution = 1:19, 1/20

40µl of B with 800µl of H2O

Dilution = 1:20, 1/21

50µl of B with 1ml of H2O

Dilution = 1:20, 1/21

25µl of B with 100µl of H2O

Dilution = 1:4, 1/5

30µl of B with 900µl of H2O

Dilution = 1:30, 1/31

26µl of B with 650µl of H2O

Dilution = 1:25, 1/26

20µl of B with 1000µl of H2O

Dilution = 1:50, 1/51

30µl of B with 450µl of H2O

Dilution = 1:15, 1/16

Exercise 2: Using H2O as a dilutant, the undermentioned dilutions of solution B were prepared.

1/10 = 10µl of B and 90µl of H2O

1+40 = 10µl of B and 400µl of H2O

1/80 = 10µl of B and 790µl of H2O

1+39 = 10µl of B and 390µl of H2O

1:10 = 10µl of B and 100µl of H2O

1/20 = 10µl of B and 190µl of H2O

1/50 = 10µl of B and 490µl of H2O

1:25 = 10µl of B and 250µl of H2O

Exercise 3: Preparation of the undermentioned consecutive dilutions

A 2-fold dilution get downing from 1/40 to make a concluding concentration of 1/640

1/40 ten 1/2 ten 1/2 ten 1/2 ten 1/2 = 1/640

In first test-tube:

10µl of B and 390µl of H2O

In the undermentioned test-tubes:

100µl of the old solution and 100µl of H2O

A 3-fold dilution get downing from 1/30 making a concluding concentration of 1/270

1/30 ten 1/3 ten 1/3 = 1/270

In first test-tube:

10µl of B and 269µl of H2O

In the undermentioned test-tubes:

100µl of the old solution and 200µl of H2O

A 5-fold dilution get downing from 1/10 making a concluding concentration of 1/1250

1/10 ten 1/5 ten 1/5 ten 1/5 = 1/1250

In first test-tube:

10µl of B and 1249µl of H2O

In the undermentioned test-tubes:

100µl of the old solution and 400µl of H2O

Six test-tubes were placed in a rack. To the first tubing 500µl of H2O were added. To each of the staying tubes 100µl of H2O were added. 20µl of solution B were added were transferred to tube 1 and assorted good. 100µl of tubing one were transferred to tube 2 and assorted good. 100µl of the contents of tubing 2 were transferred to tube 3, and the process was repeated for the staying tubing. The dilution of the serum in tubing 6 is 1/832 since the dilution of tubing 1 is 20/520 = 1/26. The dilutions are 2-fold. As a consequence 1/26 ten 1/2 ten 1/2 ten 1/2 ten 1/2 ten 1/2 = 1/832


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