Tris-buffered saline (TBS) is isotonic, notoxic buffer used in some biochemical techniques that is maintain the pH within a relatively narrow range. Tris-HCl is commonly used to make TBS buffers and has a slightly alkaline buffering capacity in the 7–9.2 range. Tris has a pKa of 8.06 at 25 °C; the pKa declines approximately 0.03 units per degree Celsius rise in temperature, which can result in relatively dramatic pH shifts when there are significant shifts in solution temperature. Tris concentration, that provides the buffering capacity, vary from 10 to 100 mM for a solution labeled as TBS. As TBS is used to emulate physiological conditions (as in animal or human body), the pH value is slightly alkaline, ranging from 7.4 to 8.0. The addition of sodium chloride allows for isotonic (mostly used 150 mM NaCl corresponds to physiological conditions: 0.9% NaCl) or hypertonic (500mM NaCl) salt concentration. A variety of concentrations of TRIS and NaCl, as well as the pH are used to refer to a “TBS” solutions, and consequently it is important to understand the specific composition for a TBS solution when used in an experiment.
Although there are many variations on TBS , a commonly “standard” formulation for 1X TBS is considered to be a solution that contains 0.05 M Tris and 0.15 M sodium chloride, pH 7.6, at 25 °C.
1X TBS Solution, 1L (50 mM Tris-Cl, pH 7.6; 150 mM NaCl)
- 1M HCl
- High purity water
- Dissolve 6.05 g Tris and 8.76 g NaCl in 800 mL of H2O.
- Adjust pH to 7.6 with 1 M HCl.
- Make volume up to 1 L with high purity distilled or deionized water.
- Once prepared, TBS is stable at 4°C for 3 months.