A
serial dilution is the stepwise
dilutionDilution may refer to:* Reducing the concentration of a chemical* Serial dilution, a common way of going about this reduction of concentration.* Homeopathic dilution* Dilution , an equation to calculate the rate a gas dilutes...
of a
substanceA chemical substance is a material with a specific chemical composition.A common example of a chemical substance is pure water; it has the same properties and the same ratio of hydrogen to oxygen whether it is isolated from a river or made in a laboratory. Some typical chemical substances are...
in
solutionIn chemistry, a solution is a homogeneous mixture composed of two or more substances. In such a mixture, a solute is dissolved in another substance, known as a solvent. Gases may dissolve in liquids, for example, carbon dioxide or oxygen in water. Liquids may dissolve in other liquids. Gases can...
. Usually the dilution factor at each step is constant, resulting in a
geometric progressionIn mathematics, a geometric progression, also known as a geometric sequence, is a sequence of numbers where each term after the first is found by multiplying the previous one by a fixed non-zero number called the common ratio. For example, the sequence 2, 6, 18, 54, ... is a geometric progression...
of the concentration in a
logarithmIn mathematics, the logarithm of a number to a given base is the power or exponent to which the base must be raised in order to produce the number....
ic fashion. A ten-fold serial dilution could be 1 M, 0.1 M, 0.01 M, 0.001 M... Serial dilutions are used to accurately create highly diluted solutions as well as solutions for
experimentIn scientific research, an experiment is a method of investigating causal relationships among variables, or to test a hypothesis. An experiment is a cornerstone of the empirical approach to acquiring data about the world and is used in both natural sciences and social sciences...
s resulting in concentration curves with a
logarithmic scaleA logarithmic scale is a scale of measurement that uses the logarithm of a physical quantity instead of the quantity itself.A simple example is when equally-spaced divisions on the vertical axis of a chart are labelled 1, 10, 100, 1000, instead of 1, 2, 3, 4.Presentation of data on a logarithmic...
. A tenfold dilution for each step is called a
logarithmic dilution or
log-dilution, a 3.16-fold (10
0.5-fold) dilution is called a
half-logarithmic dilution or
half-log dilution, and a 1.78-fold (10
0.25-fold) dilution is called a
quarter-logarithmic dilution or
quarter-log dilution.
A
serial dilution is the stepwise
dilutionDilution may refer to:* Reducing the concentration of a chemical* Serial dilution, a common way of going about this reduction of concentration.* Homeopathic dilution* Dilution , an equation to calculate the rate a gas dilutes...
of a
substanceA chemical substance is a material with a specific chemical composition.A common example of a chemical substance is pure water; it has the same properties and the same ratio of hydrogen to oxygen whether it is isolated from a river or made in a laboratory. Some typical chemical substances are...
in
solutionIn chemistry, a solution is a homogeneous mixture composed of two or more substances. In such a mixture, a solute is dissolved in another substance, known as a solvent. Gases may dissolve in liquids, for example, carbon dioxide or oxygen in water. Liquids may dissolve in other liquids. Gases can...
. Usually the dilution factor at each step is constant, resulting in a
geometric progressionIn mathematics, a geometric progression, also known as a geometric sequence, is a sequence of numbers where each term after the first is found by multiplying the previous one by a fixed non-zero number called the common ratio. For example, the sequence 2, 6, 18, 54, ... is a geometric progression...
of the concentration in a
logarithmIn mathematics, the logarithm of a number to a given base is the power or exponent to which the base must be raised in order to produce the number....
ic fashion. A ten-fold serial dilution could be 1 M, 0.1 M, 0.01 M, 0.001 M... Serial dilutions are used to accurately create highly diluted solutions as well as solutions for
experimentIn scientific research, an experiment is a method of investigating causal relationships among variables, or to test a hypothesis. An experiment is a cornerstone of the empirical approach to acquiring data about the world and is used in both natural sciences and social sciences...
s resulting in concentration curves with a
logarithmic scaleA logarithmic scale is a scale of measurement that uses the logarithm of a physical quantity instead of the quantity itself.A simple example is when equally-spaced divisions on the vertical axis of a chart are labelled 1, 10, 100, 1000, instead of 1, 2, 3, 4.Presentation of data on a logarithmic...
. A tenfold dilution for each step is called a
logarithmic dilution or
log-dilution, a 3.16-fold (10
0.5-fold) dilution is called a
half-logarithmic dilution or
half-log dilution, and a 1.78-fold (10
0.25-fold) dilution is called a
quarter-logarithmic dilution or
quarter-log dilution. Serial dilutions are widely used in experimental sciences, including
biochemistryBiochemistry is the study of the chemical processes in living organisms. It deals with the structure and function of cellular components such as proteins, carbohydrates, lipids, nucleic acids and other biomolecules....
,
pharmacologyPharmacology is the study of drug action. More specifically, it is the study of the interactions that occur between a living organism and exogenous chemicals that alter normal biochemical function. If substances have medicinal properties, they are considered pharmaceuticals...
,
microbiologyMicrobiology is the study of microorganisms, which are unicellular or cell-cluster microscopic organisms. This includes eukaryotes such as fungi and protists, and prokaryotes. Viruses, though not strictly classed as living organisms, are also studied...
, and
physicsPhysics is a natural science; it is the study of matter and its motion through spacetime and all that derives from these, such as energy and force...
, as well as in
homeopathyHomeopathy is a form of alternative medicine, first proposed by German physician Samuel Hahnemann in 1796, that treats patients with heavily diluted preparations which are thought to cause effects similar to the symptoms presented...
.
Dilution scheme
For a ten-fold logarithmic serial dilution on a 1 ml scale, vials are filled with 1 ml solvent and 0.111 ml solution is serially transferred with thorough mixing after every dilution step. For a half-logarithmic serial dilution, 0.462 ml solution are transferred and for a quarter-log serial dilution 1.285 ml are transferred at each step.
The general formula is:
Volume transferred = Volume prefilled / (dilution factor - 1)
In biology and medicine
In
biologyBiology is the natural science concerned with the study of life and living organisms, including their structure, function, growth, origin, evolution, distribution, and taxonomy...
and
medicineMedicine is the art and science of healing. It encompasses a range of health care practices evolved to maintain and restore health by the prevention and treatment of illness....
, besides the more conventional uses described above, serial dilution may also be used to reduce the concentration of microscopic organisms or cells in a sample. As, for instance the number and size of bacterial colonies that grow on an
agarAgar or agar agar is a gelatinous substance derived from seaweed. Historically and in a modern context, it is chiefly used as an ingredient in desserts throughout Japan, but in the past century has found extensive use as a solid substrate to contain culture medium for microbiological work...
plate in a given time is concentration-dependent, and since many other diagnostic techniques involve physically counting the number of micro-organisms or cells on specials printed with grids (for comparing concentrations of two organisms or cell types in the sample) or wells of a given volume (for absolute concentrations), dilution can be useful for getting more manageable results. Serial dilution is also a cheaper and simpler method for preparing
cultures from a single cellIn biology, axenic describes a culture of an organism that is entirely free of all other "contaminating" organisms. The earliest axenic cultures were of bacteria or unicellular eukaryotes, but axenic cultures of many multicellular organisms are also possible.-Preparation:Axenic cultures of...
than
optical tweezersAn optical tweezer is a scientific instrument that uses a focused laser beam to provide an attractive or repulsive force , depending on the refractive index mismatch to physically hold and move microscopic dielectric objects...
and
micromanipulatorA micromanipulator is a device which is used to physically interact with a sample under a microscope, where a level of precision of movement is necessary that cannot be achieved by the unaided human hand....
s.
In homeopathy
Serial dilution is one of the core foundational practices of
homeopathyHomeopathy is a form of alternative medicine, first proposed by German physician Samuel Hahnemann in 1796, that treats patients with heavily diluted preparations which are thought to cause effects similar to the symptoms presented...
, with "succussion", or shaking, occurring between each dilution. In homeopathy, serial dilutions (called potentisation) are often taken so far that by the time the last dilution is completed, no molecules of the original substance are likely to remain.
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