What are common buffer solutions made of?

Acids commonly used as buffer solutions are a solution composed of weak acids and their conjugates. Common buffer systems are:

1. Weak acid and its salts (such as HAC---NAAC).

2. Weak alkali and its salt (NH3·H2O

nh4cl）

3. Acid salts with multiple weak acids.

and its corresponding secondary salts (such as NaH2PO4--- Na2HPO4).

The buffer systems commonly used in biochemical laboratories mainly include phosphoric acid and citric acid.

Carbonic acid, acetic acid.

Barbituric acid, TRIS (trimethylolaminomethane.

Biochemical experiments or research work should be careful to choose the buffer system, because sometimes the factor that affects the experimental results is not the pH value of the buffer.

It's an ion in the buffer. Buffers such as borate, citrate, phosphate, and trimethylolmethane can produce unwanted chemical reactions.

Borate: Borate forms a double salt with many compounds, such as sucrose.

Citrate: Citrate ions are easily combined with calcium, so it cannot be used in the presence of calcium ions.

Phosphate: In some experiments, it is an inhibitor of enzymes or even a metabolite, and heavy metals are easily precipitated from solution in the form of phosphate. And it has very little cushioning capacity when it is above.

Tris(hydroxymethyl)aminomethane: It can work with heavy metals, but it also acts as an inhibitor in some systems. Its main disadvantage is the temperature effect.

This is often overlooked, as the pH at room temperature is the TRIS buffer, 4 is at 37, and the hydrogen concentration of the 4 prepared buffer increases by a factor of 10 when measured at 37. In the following, its cushioning capacity is extremely unsatisfactory.

Buffer solution refers to a mixed solution composed of weak acid and its salt, weak base and its salt, which can offset and reduce the influence of external reinforcing acid or strong base on the pH of the solution to a certain extent, so as to keep the pH value of the solution relatively stable.

When a certain amount of acid and base is added to some solutions, it has the effect of hindering the change of pH of the solution, which is called buffering, and such a solution is called buffering solution. Mixed solutions of weak acids and their salts (such as Hoac and Naoac), and mixed solutions of weak bases and their salts (such as NH3·H2O and NH4Cl) are buffer solutions.

The buffer solution consists of conjugated acid-base pairs of sufficient concentrations. Among them, the one that can resist the foreign strong base is called conjugate acid, and the one that can resist the foreign strong acid is called the conjugate base, and this pair of conjugate acid and base is usually called a buffer pair, a buffer or a buffer system, and there are three main types of common buffer pairs.

1 Weak acids and their corresponding salts e.g., hoac-naoac (actually oac-); h2co3-nahco3；H2C8H4O4-KhC8H4O4 (phthalic acid-potassium hydrogen phthalate); H3bo3-Na2B4O7 (H2Bo-3 is produced after hydrolysis of sodium tetraborate).

2 Acid salts of multiple weak acids and their corresponding secondary salts, e.g., NaHCO3-NA2CO3; nah2po4-na2hpo4；NaH2C5Ho7 (sodium dihydrogen citrate)-Na2HC6H5O7; khc8h4o4-k2c8h4o4。

3 Weak bases and their corresponding salts: e.g. NH3-NH+4Cl-; RNH2-RNH+3A- (primary amine and its salts); Tris-Trish+A- (tris-hydroxymethylol and its salts).

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The nature of the buffer solution is: a mixed solution composed of weak acid and its salt, weak base and its sodium salt, which can offset and alleviate the addition to a certain extentStrong acidsor a strong base against the solutionpHthe effect of keeping the solutionpHRelatively stable.

The buffer solution is inorganic chemistry.

and an important concept in analytical chemistry, a buffer solution is a solution that has the ability to maintain the relative stability of pH. The pH value does not change significantly within a certain range due to dilution or addition of a small amount of acid or base, and the buffer solution is based on the amount of conjugated acid-base pair and its substance.

Different with different pH and buffer capacity.

Characteristics of the buffer solution.

When a certain amount of acid and base is added to some solutions, it has the effect of hindering the pH change of the solution, which is called buffering, and such a solution is called buffer solution. Mixed solutions of weak acids and their salts (such as HAC and Naac), mixed solutions of weak bases and their salts (such as NH3H2O and NH4Cl) are buffer solutions.

The buffering effect of a buffer solution consisting of a weak acid HA and its salt Naa on the acid is due to the presence of a sufficient amount of alkali A- in the solution. When a certain amount of strong acid is added to this solution, the H ion is essentially consumed by the A-ion: so the pH of the solution is almost constant; When a certain amount of strong base is added.

The weak acid HA present in the solution depletes the OH- ion and hinders the change of pH.

The above internal clear beam capacity reference: Encyclopedia - buffer solution.

1. The pH value of the buffer is related to the ionization equilibrium constant k of the acid and the concentration of salts and acids. When the concentration of acid and salt is equal, the pH value of the solution is the same as the PK value. When the concentration of acid and salt increases or decreases in equal proportions, the pH value of the solution does not change.

When the acid and salt concentrations are equal, the buffering efficiency of the buffer is high.

2. Add a small amount of strong acid or strong alkali to the buffer solution, and the pH value of the solution does not change much, but if the amount of acid and alkali is added, the buffer solution will lose its buffering effect. This shows that there is a limit to its buffering capacity.

3. The buffering capacity of the buffer solution is related to the concentration of the components that make up the buffer solution. and the composition of the buffer solution, which has a greater buffering capacity than the buffer solution of and. This is confirmed by calculations.

However, the concentration of the components of the buffer solution should not be too large, otherwise, the interaction between ions cannot be ignored.

Buffer solution (English: buffer solution) refers to ".Weak acidand the salts of the conjugated bases" or "the salts of the weak bases and their conjugated acids" are prepared to slow down the pH change when a certain amount of other substances are added.

The reason why two pairs of substances are used in the above definition is that the reaction can be buffered towards an acid or base at the same time, such as a mixed solution of acetic acid and sodium acetate.

It's a buffer solution. If hydrochloric acid is added, the pH will not drop too quickly, because hydrochloric acid will react with sodium acetate to form acetic acid. Conversely, if sodium hydroxide is added.

The pH does not increase too quickly because sodium hydroxide reacts with acetic acid to form sodium acetate.

in many chemical reactions.

, a buffer solution is used to make the pH of the solution.

Keep it constant. Buffer solutions are of great significance for the emergence and evolution of life, because most organisms can only grow within a certain pH range, for example, blood is a buffer solution.

Apply. Buffer solutions have many uses, such as the presence of dihydrogen phosphate-hydrogen phosphate and sodium carbonate-sodium bicarbonate in human blood.

Maintain the pH of the blood between to maintain the activity of the enzyme.

In industry, buffer solutions are often used to adjust the pH of dyes. The buffer solution can also be used to calibrate the pH meter.

The composition of the buffer solution is different from that of the general solution: the difference is that when distilled water is added at the same time, when the volume of distilled water is less than 50% of the original volume of the solution, the pH value of the ordinary solution will change (except for the neutral salt solution), and the pH value of the buffer solution will remain basically unchanged.

The pH of ordinary buffer solutions is mostly in a range, such as ammonia-ammonium chloride and acetate-sodium acetate, which usually maintains the pH of a certain system; However, the pH of a standard buffer solution is a fixed value and is usually used to calibrate the pH meter. The pH basic change solution that can resist a small amount of acid-base or dilute a small number of multiples of the system is called a buffer solution, and the buffer solution is generally composed of conjugated acid-base or amphoteric substance group.

Preparation method: As long as you know the pH of the buffer pair, and the pH of the buffer to be prepared (and the total concentration of the buffer required), you can calculate the amount of [salt] and [acid] according to the formula. This algorithm involves logarithmic conversion, which is more troublesome, and the predecessors artificially reduce the calculation trouble of later generations, and has summarized the relationship between the pH value and the amount of counterions in the buffer and listed it.

As long as we know the pH of the buffer to be prepared, we can calculate the proportion and amount of buffer to be used by looking up the table. For example, a 100 nm concentration is formulated as a phosphate buffer.

There are generally three types of composition of buffer solution.

Weak acids and weak acids and strong alkaline salts.

Weak alkali and strong acid and weak alkali salt.

Several acidic salts of moderately strong acid phosphoric acid.

The buffer solution is mainly used to control the reaction conditions of some reactions, that is, acidity and alkalinity, some chemical reactions are carried out under different acidity and alkaline conditions, the degree of reaction or the components generated are not the same, in order to make the reaction in the direction of the positive reaction, improve the conversion rate of the reaction, add buffer solution to the reaction solution to achieve the above required effects.