Density | 1.004 g/mL at 25 °C(lit.) |
Use | Uses the buffer solution has many uses, for example, human blood contains many pairs of buffer pairs, such as dihydrogen phosphate-hydrogen phosphate, carbonate-sodium bicarbonate, etc., to maintain the pH of the blood between 7.35 and 7.45, to maintain the activity of the enzyme. In industry, buffer solutions are often used to adjust the pH of dyes. The buffer solution may also be used for the calibration of the pH meter. |
Hazard Symbols | Xi - Irritant |
Risk Codes | 36/37/38 - Irritating to eyes, respiratory system and skin. |
Safety Description | S26 - In case of contact with eyes, rinse immediately with plenty of water and seek medical advice. S36 - Wear suitable protective clothing. |
overview
For external factors (such as acid, alkali or dilution), it can play a role in a certain extent, and the solution that keeps the acidity or pH value of the solution basically unchanged is called a buffer solution. Buffer solutions are usually composed of weak acids and weak acid salts (such as HAc and NaAc), weak bases and weak alkali salts (such as NH3 and NH4Cl), and acid salts with different basicity (such as NaH2PO4 and Na2HPO4).
example
Acids commonly used as buffer solutions The solution composed of weak acids and their conjugate acid salts has a buffer effect. The buffer systems commonly used in biochemical laboratories mainly include phosphoric acid, citric acid, carbonic acid, acetic acid, barbituric acid, Tris (trihydroxymethylaminomethane) and other systems. The buffer system should be carefully selected in biochemical experiments or research work, because sometimes The factor affecting the experimental results is not the pH value of the buffer, but a certain ion in the buffer. Buffers such as borate, citrate, phosphate and trimethylmethyl methane may all produce unwanted chemical reactions.
Borate: Borate forms double salts with many compounds, such as sucrose.
Citrate: Citrate ions are easy to combine with calcium, so they cannot be used in the presence of calcium ions.
Phosphate: In some experiments, it is an enzyme inhibitor or even a metabolite. Heavy metals are easily precipitated from the solution in the form of phosphate. And it has very little buffering capacity above pH7.5.
Trihydroxymethyl aminomethane: It can act with heavy metals, but it also plays an inhibitory role in some systems. Its main disadvantage is the temperature effect. This is often overlooked. Tris buffer with 7.8 pH at room temperature is 8.4 at 4 ℃ and 7.4 at 37 ℃. Therefore, when the buffer prepared at 4 ℃ is measured at 37 ℃, its hydrogen ion concentration increases 10 times. Below pH 7.5, its buffering capacity is extremely unsatisfactory.