Today we will learn together the common analytical classifications and their principles in analytical chemistry. So, first let's understand what analytical chemistry is.

　　Analytical chemistry is the study of obtaining information on the chemical composition and structure of substances, analytical methods and related theories. It addresses the problems of determining which components are contained in a substance, how these components are present in the substance, what the relative content of each component is, and how to characterize the chemical structure of a substance.

　　Analytical chemistry can be divided according to the principle of chemical analysis and determination: titrimetric analysis and gravimetric analysis.

　　1. Titration analysis method

　　This analysis is called titrimetric analysis or volumetric analysis, which is based on the concentration and volume of the standard solution consumed for titration and the stoichiometric relationship of the chemical reaction between the substance being measured and the standard solution.

　　The four major equilibria of solutions are used: acid-base (ionization) equilibrium, redox equilibrium, complexation (ligand) equilibrium, and precipitation-dissolution equilibrium. We can classify them according to their reaction types as:

　　1) Acid-base titration: measure the acidity and acid-base content of various acids and bases.

　　2) Redox titration: Measurement of substances with redox properties.

　　3) complex titration method: measuring the content of metal ions.

　　4) precipitation titration: measurement of halogens and silver.

　　Commonly used titration volume instruments: including pipettes, pipettes, acid burettes, volumetric flasks, beakers, measuring cylinders, conical flasks, etc.

　　2. Weight analysis method

　　By appropriate methods such as precipitation, volatilization, electrolysis, etc., the component to be measured into another pure, chemical composition of a fixed compound and other components of the sample can be separated, and then weighed its mass, according to the mass weighed to calculate the content of the component to be measured, so the analysis method is called weight analysis. Weight analysis is suitable for constant analysis of components to be measured content greater than 1%, its characteristics are high accuracy, so this method is often used for arbitration analysis, but the operation is troublesome and time-consuming.

　　The basic operations of gravimetric analysis include: sample dissolution, precipitation, filtration, washing, drying and cauterization.

　　Analytical chemistry can be classified by instrument: chromatography, mass spectrometry, photochemical analysis, analytical instrumentation, optical analysis, thermal analysis, etc.