Tris, or tris(hydroxymethyl)aminomethane, or known during medical use as tromethamineorTHAM, is an organic compound with the formula (HOCH2)3CNH2. It is extensively used in biochemistry and molecular biology as a component of buffer solutions[2] such as in TAE and TBE buffers, especially for solutions of nucleic acids. It contains a primary amine and thus undergoes the reactions associated with typical amines, e.g., condensations with aldehydes. Tris also complexes with metal ions in solution.[3] In medicine, tromethamine is occasionally used as a drug, given in intensive care for its properties as a buffer for the treatment of severe metabolic acidosis in specific circumstances.[4][5] Some medications are formulated as the "tromethamine salt" including Hemabate (carboprost as trometamol salt), and "ketorolac trometamol".[6] In 2023 a strain of Pseudomonas hunanensis was found to be able to degrade TRIS buffer.[7]
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| Names | |
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| Preferred IUPAC name
2-Amino-2-(hydroxymethyl)propane-1,3-diol | |
| Other names
TRIS, Tris, Tris base, Tris buffer, Trizma, Trisamine, THAM, Tromethamine, Trometamol, Tromethane, Trisaminol, Tris(hydroxymethyl)aminomethane | |
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 YY | |
3D model (JSmol) |
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| DrugBank | |
| ECHA InfoCard | 100.000.969 
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PubChem CID |
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| RTECS number |
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| UNII |
Y |
CompTox Dashboard (EPA) |
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| Properties | |
| C4H11NO3 | |
| Molar mass | 121.136 g·mol−1 |
| Appearance | White crystalline powder |
| Density | 1.328g/cm3 |
| Melting point | >175-176 °C (448-449 K) |
| Boiling point | 219 °C (426 °F; 492 K) |
| ~50 g/100 mL (25 °C) | |
| Acidity (pKa) | 8.07 (conjugate acid) |
| Pharmacology | |
| B05BB03 (WHO) B05XX02 (WHO) | |
| Hazards[1] | |
| Occupational safety and health (OHS/OSH): | |
Main hazards |
Irritant |
| GHS labelling: | |
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| Warning | |
| H315, H319, H335 | |
| P261, P264, P271, P280, P302+P352, P304+P340, P305+P351+P338, P312, P332+P313, P362, P403+P233, P405 | |
| NFPA 704 (fire diamond) |
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| Flash point | Non-flammable |
| Safety data sheet (SDS) | External MSDS |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |
The conjugate acid of tris has a pKa of 8.07 at 25 °C, which implies that the buffer has an effective pH range between 7.1 and 9.1 (pKa ± 1) at room temperature.
Tris is prepared industrially by the exhaustive condensation of nitromethane with formaldehyde under basic conditions (i.e. repeated Henry reactions) to produce the intermediate (HOCH2)3CNO2, which is subsequently hydrogenated to give the final product.[11]
The useful buffer range for tris (pH 7–9) coincides with the physiological pH typical of most living organisms. This, and its low cost, make tris one of the most common buffers in the biology/biochemistry laboratory. Tris is also used as a primary standard to standardize acid solutions for chemical analysis.
Tris is used to increase permeability of cell membranes.[12] It is a component of the Moderna COVID-19 vaccine[13] and the Pfizer-BioNTech COVID-19 vaccine for use in children 5 through 11 years of age.[14]
Tris (usually known as THAM in this context) is used as alternative to sodium bicarbonate in the treatment of metabolic acidosis.[15][16]
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