The difference between Tris-Hcl and phosphate buffer
The scientific name of Tris is tris-hydroxymethylaminomethane, and Tris-Cl is Tris-HCl, but the writing method is different. Tris-HCl is to add appropriate amount of hydrochloric acid to the solution of Tris-base to adjust to the required PH value. Tris buffers are used more and more in biochemical research, and there is a tendency to exceed phosphate buffers. For example, Tris buffers have been used in SDS-polyacrylamide gel electrophoresis, and phosphates are rarely used.
Tris Biological buffer
1. Advantages of Tris-HCl buffer:
（1）The commonly used effective pH range is in the "neutral" range: pH = 7.5 ~ 8.5
（2）Tris-HCl buffer is stable and has good compatibility with physiological body fluids (Tris-HCl will not form precipitates with calcium and magnesium ions; on the contrary, phosphates will cause precipitation with calcium and magnesium ions)
（3）And the ionic strength of Tris-HCl buffer solution with the same pH and the same concentration is low, which is especially important for the determination of enzymes, because the large ionic strength is easy to inactivate some enzymes. Therefore, it is sometimes better to use Tris-HCl instead of phosphate buffer.
Disadvantages of Tris-HCl buffer:
（1）The temperature effect is large, and the temperature change has a great influence on the pH value of the buffer, namely: △pKa/℃=－0.031, for example: the pH of the buffer at 4℃=8.4, then the pH at 37℃=7.4, so It must be prepared at the use temperature. Tris-HCl buffer solution prepared at room temperature cannot be used at 0℃～4℃. Once the temperature changes, the pH will change significantly, and the enzyme activity will be changed.
（2）The pH value of the buffer solution is greatly affected by the concentration of the solution. The buffer solution is diluted ten times, and the change in pH value is greater than 0.1;
（3）This buffer has certain interference effect on certain pH electrodes, so use an electrode compatible with Tris solution.
（4） It is easy to absorb CO2 in the air, so the prepared buffer should be tightly sealed.
2. Advantages of phosphate buffer:
（1）Phosphate is the most widely used biological buffer in biochemical research. Because they are second-order dissociation and have two pKa values, the buffers prepared with them have the widest pH range: ① with acidic buffer Use NaH2PO4, pH=1~4; ② mix the two kinds of phosphates used in the neutral buffer, pH=6-8; ③ use Na2HPO4, pH=10-12 in the alkaline buffer.
（2） It can be easily prepared into buffer solutions of various concentrations;
（3）The pH is less affected by temperature;
（4）The pH change of the buffer after dilution is small, for example, the pH change after dilution ten times is less than 0.1.
（5）When preparing phosphate buffer solution, potassium salt is better than sodium salt, because potassium salt has better solubility than sodium salt at low temperature, but when preparing buffer solution for SDS-polyacrylamide gel electrophoresis, Only sodium phosphate can be used instead of potassium phosphate, because SDS (sodium dodecyl sulfate) will form insoluble potassium dodecyl sulfate with potassium salt.
Disadvantages of phosphate buffer:
（1）It is easy to associate with common calcium, magnesium and heavy metal ions to form a precipitate;
（2）It will inhibit certain biochemical processes, such as the catalytic effect on certain enzymes will have a certain inhibitory effect.
In view of the advantages and disadvantages of the above Tris salt buffer and phosphate buffer, we must choose the appropriate buffer system according to the actual situation to ensure the smooth progress of the experiment. Of course, the choice of buffer raw material manufacturers is also very important. Buffer products have strict quality inspection standards and are checked layer by layer to ensure that mature and stable products are provided to our customers.
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