Phosphate buffered saline
Encyclopedia
Phosphate buffered saline (abbreviated PBS) is a buffer solution
commonly used in biological research
. It is a water-based salt solution containing sodium chloride
, sodium phosphate, and, in some formulations, potassium chloride
and potassium phosphate
. The buffer
's phosphate groups help to maintain a constant pH
. The osmolarity and ion concentrations of the solution usually match those of the human body (isotonic
).
is also used to disengage attached and clumped cells. Divalent metals such as zinc
, however, cannot be added as this will result in precipitation. For these types of applications, Good's buffers
are recommended.
The simplest way to prepare a PBS solution is to use PBS buffer tablets. They are formulated to give a ready to use PBS solution upon dissolution in a specified quantity of distilled water. They are available in the standard volumes: 100, 200, 500 and 1000 mL .
If used in cell culturing, the solution can be dispensed into aliquots and sterilized by autoclaving (20 min, 121°C, liquid cycle). Sterilization may not be necessary depending on its use. PBS can be stored at room temperature, but may warrant refrigeration to prevent bacterial growth if solution is not sterile and is kept for long periods of time. However, concentrated stock solutions may precipitate when cooled and should be kept at room temperature until precipitate has completely dissolved before use.
Buffer solution
A buffer solution is an aqueous solution consisting of a mixture of a weak acid and its conjugate base or a weak base and its conjugate acid. It has the property that the pH of the solution changes very little when a small amount of strong acid or base is added to it. Buffer solutions are used as a...
commonly used in biological research
Biology
Biology is a natural science concerned with the study of life and living organisms, including their structure, function, growth, origin, evolution, distribution, and taxonomy. Biology is a vast subject containing many subdivisions, topics, and disciplines...
. It is a water-based salt solution containing sodium chloride
Sodium chloride
Sodium chloride, also known as salt, common salt, table salt or halite, is an inorganic compound with the formula NaCl. Sodium chloride is the salt most responsible for the salinity of the ocean and of the extracellular fluid of many multicellular organisms...
, sodium phosphate, and, in some formulations, potassium chloride
Potassium chloride
The chemical compound potassium chloride is a metal halide salt composed of potassium and chlorine. In its pure state, it is odorless and has a white or colorless vitreous crystal appearance, with a crystal structure that cleaves easily in three directions. Potassium chloride crystals are...
and potassium phosphate
Potassium phosphate
Potassium phosphate is a generic term for the salts of potassium and phosphate ions including:* Monopotassium phosphate * Dipotassium phosphate * Tripotassium phosphate...
. The buffer
Buffer
Buffer may refer to:*Buffer state, a country lying between two potentially hostile greater powers, thought to prevent conflict between them* Buffer zone, any area that keeps two or more other areas distant from one another, may be demilitarized...
's phosphate groups help to maintain a constant pH
PH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...
. The osmolarity and ion concentrations of the solution usually match those of the human body (isotonic
Isotonic
The term isotonic may refer to;*Isotonic for the term associated with muscle contraction*An isotone in nuclear physics*Sports drinks are sometimes designed in an isotonic way to assist athletes rehydrate while balancing electrolytes...
).
Applications
PBS has many uses because it is isotonic and non-toxic to cells. It can be used to dilute substances. It is used to rinse containers containing cells. For example, PBS with EDTAEDTA
Ethylenediaminetetraacetic acid, widely abbreviated as EDTA , is a polyamino carboxylic acid and a colourless, water-soluble solid. Its conjugate base is named ethylenediaminetetraacetate. It is widely used to dissolve limescale. Its usefulness arises because of its role as a hexadentate ligand...
is also used to disengage attached and clumped cells. Divalent metals such as zinc
Zinc
Zinc , or spelter , is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...
, however, cannot be added as this will result in precipitation. For these types of applications, Good's buffers
Good's buffers
Good's buffers are twelve buffering agents selected and described by Norman Good and colleagues in 1966. Good selected the buffers based on a number of criteria which make them candidates for use in biochemistry and biological research...
are recommended.
Preparation
There are many different ways to prepare PBS. Some formulations do not contain potassium, while others contain calcium or magnesium. Generally, PBS contains the following constituents:| Salt | Concentration | Concentration |
|---|---|---|
| (—) | (mmol/L) | (g/L) |
| NaCl | 137 | 8.01 |
| KCl | 2.7 | 0.20 |
| Na2HPO4 • 2 H2O | 10 | 1.78 |
| KH2PO4 | 2.0 | 0.27 |
| pH | 7.4 | 7.4 |
The simplest way to prepare a PBS solution is to use PBS buffer tablets. They are formulated to give a ready to use PBS solution upon dissolution in a specified quantity of distilled water. They are available in the standard volumes: 100, 200, 500 and 1000 mL .
If used in cell culturing, the solution can be dispensed into aliquots and sterilized by autoclaving (20 min, 121°C, liquid cycle). Sterilization may not be necessary depending on its use. PBS can be stored at room temperature, but may warrant refrigeration to prevent bacterial growth if solution is not sterile and is kept for long periods of time. However, concentrated stock solutions may precipitate when cooled and should be kept at room temperature until precipitate has completely dissolved before use.