Standard solution refers to a reagent solution with an accurate known concentration, and titrators are commonly used in titration analysis. In other analytical methods, the standard solution is used to draw working curves or as a calculation standard.

A solution of a particular concentration parameter, such as a standard solution of Cl or Fe, when tested with a standard solution instead of a sample, the result should be consistent with the concentration of a known standard solution. If the results match, the test was performed correctly. According to the different uses, the standard solution is divided into standard solution for titration analysis, standard solution for impurity determination and standard solution for pH measurement.

1, standard titration solution

The standard solution for titration analysis is mainly used to determine the main component or major component in the sample, and there are two preparation methods:

One is directly prepared with primary or secondary standard substances (also known as "reference reagents");

The second is to use the reagent of the above specifications to prepare a solution close to the required concentration, and then use the standard material to determine (called "calibration").

GB601-88 "Preparation of standard solution for titration analysis" is the only standard method in China. The standard titration solution is expressed by the molar concentration of the substance, the symbol is c(B), the unit is mol·L-1, meaning that the amount of the substance (mol) contained in the solution per liter of titrant B as the basic unit.

2, impurity determination with standard solution

Standard solution for impurity determination is also known as standard solution for instrument analysis, GB602-88 "Preparation of standard solution for impurity determination" gives 83 preparation methods for impurity standard solution. The amount of elements, ions, compounds, or groups contained in the solution, expressed in milligrams per milliliter. Most of the standard solution concentrations specified in this standard are 0.1mg·mL-1, a few are 1mg·mL-1, and only one is 10mg·mL-1. Under the specified concentration, the solution is relatively stable and can be called a reserve liquid, and when a lower concentration is needed, it can be diluted as required to make a standard series solution.

3, pH measurement with standard solution

When measuring the acidity of a solution with a pH meter, the pH meter must first be calibrated with a pH standard solution.

The above content is the introduction of the explanation of the standard solution term, when we use chemical analysis or instrumental analysis to analyze and determine, often need to configure a standard solution, the standard solution is known its main composition or other characteristics of the value of the solution.