Good's buffers are twelve buffering agent

Buffering agent

A buffering agent is a weak acid or base used to maintain the acidity of a solution at a chosen value. The function of a buffering agent is to prevent a rapid change in pH when acids or bases are added to the solution. Buffering agents have variable properties—some are more soluble than others;...

s 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

Biochemistry

Biochemistry, sometimes called biological chemistry, is the study of chemical processes in living organisms, including, but not limited to, living matter. Biochemistry governs all living organisms and living processes...

 and biological

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...

 research. Many remain staples in modern biology laboratories.

Selection criteria

Good sought to identify buffering compounds which met several criteria likely to be of value in biological research.

1. pK_a
   PKA
   PKA, pKa, or other similar variations may stand for:* pKa, the symbol for the acid dissociation constant at logarithmic scale* Protein kinase A, a class of cAMP-dependent enzymes* Pi Kappa Alpha, the North-American social fraternity...
   
   . Because most biological reactions take place at near-neutral 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...
   
    between 6 and 8, ideal buffers would have pK_a values in this region to provide maximum buffering capacity there.
2. Solubility. For ease in handling and because biological systems are in aqueous systems, good solubility in water was required. Low solubility in nonpolar solvents (fats, oils, and organic solvents) was also considered beneficial, as this would tend to prevent the buffer compound from accumulating in nonpolar compartments in biological systems: cell membrane
   Cell membrane
   The cell membrane or plasma membrane is a biological membrane that separates the interior of all cells from the outside environment. The cell membrane is selectively permeable to ions and organic molecules and controls the movement of substances in and out of cells. It basically protects the cell...
   
   s and other cell compartments.
3. Membrane impermeability. Ideally, a buffer will not readily pass through cell membranes, this will also reduce the accumulation of buffer compound within cell
   Cell (biology)
   The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....
   
   s.
4. Minimal salt effects. Highly ionic buffers may cause problems or complications in some biological systems.
5. Influences on dissociation. There should be a minimum influence of buffer concentration, temperature, and ionic composition of the medium on the dissociation of the buffer.
6. Well-behaved cation interactions. If the buffers form complex
   Complex (chemistry)
   In chemistry, a coordination complex or metal complex, is an atom or ion , bonded to a surrounding array of molecules or anions, that are in turn known as ligands or complexing agents...
   
   es with cationic ligand
   Ligand
   In coordination chemistry, a ligand is an ion or molecule that binds to a central metal atom to form a coordination complex. The bonding between metal and ligand generally involves formal donation of one or more of the ligand's electron pairs. The nature of metal-ligand bonding can range from...
   
   s, the complexes formed should remain soluble. Ideally, at least some of the buffering compounds will not form complexes.
7. Stability. The buffers should be chemically stable, resisting enzymatic
   Enzyme
   Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
   
    and non-enzymatic degradation.
8. Optical absorbance. Buffers should not absorb visible or ultraviolet
   Ultraviolet
   Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...
   
    light at wavelengths longer than 230 nm so as not to interfere with commonly-used spectrophotometric
   Spectrophotometry
   In chemistry, spectrophotometry is the quantitative measurement of the reflection or transmission properties of a material as a function of wavelength...
   
    assays.
9. Ease of preparation. Buffers should be easily prepared and purified from inexpensive materials.

Good's buffers

The twelve buffers selected by Good are tabulated below.

Buffer	pKa PKA PKA, pKa, or other similar variations may stand for:* pKa, the symbol for the acid dissociation constant at logarithmic scale* Protein kinase A, a class of cAMP-dependent enzymes* Pi Kappa Alpha, the North-American social fraternity...  at 20°C	ΔpKa/°C
MES MES (buffer) MES is the common name for the compound 2-ethanesulfonic acid. Its chemical structure contains a morpholine ring. It has a molecular weight of 195.2 and the chemical formula is C6H13NO4S...	6.15	-0.011
ADA	6.6	-0.011
PIPES PIPES PIPES is the common name for piperazine-N,N′-bis, and frequently used buffering agent in biochemistry. It is an ethanesulfonic acid buffer developed by Good et al. in the 1960s.-Applications:...	6.8	-0.0085
ACES ACES (buffer) ACES is the common abbreviation for the compound N--2-aminoethanesulfonic acid.ACES is one of Good's buffers developed in the 1960s to provide buffers with pH ranging from 6.15-8.35 for use in various applications. With a pKa of 6.9, it is often used as a buffering agent in biological and...	6.9	-0.020
Cholamine chloride	7.1	-0.027
BES	7.15	-0.016
TES TES (buffer) TES is used to make buffer solutions. It has a pKa value of 7.550 . It is one of the Good's buffers and can be used to make buffer solutions in the pH range 6.8–8.2....	7.5	-0.020
HEPES HEPES HEPES is a zwitterionic organic chemical buffering agent; one of the twelve Good's buffers...	7.55	-0.014
Acetamidoglycine	7.7	-
Tricine Tricine Tricine is an organic compound that is used in buffer solutions. The name tricine comes from tris and glycine from which it was derived. It is a zwitterionic amino acid with a useful buffering range of pH 7.4-8.8. It is a white crystalline powder that is moderately soluble in water. It has a pH...	8.15	-0.021
Glycinamide	8.2	-0.029
Bicine Bicine Bicine is an organic compound used as a buffering agent. It is one of Good's buffers and has a pKa of 8.35 at 20 °C....	8.35	-0.018