Analysis requirements

Measurement principle

Analysis object: inorganic/organic extension

The difference between the sample dosage and the content of the component to be tested

Nature of work: routine analysis, arbitration analysis

in accordance with

Determination requirements, components to be tested and their content, properties of components to be tested

Properties of coexisting components and their impact on determination, separation and enrichment of components to be measured

Requirements and countermeasures for measurement accuracy and sensitivity

Existing conditions, cost of measurement, and time requirements to complete the measurement

Three major changes

The first time: At the end of the 19th century and the beginning of the 20th century, the establishment of the four equilibrium theories of solutions transformed analytical chemistry from a technology to a science.

The second time: before and after World War II, due to the development of physics/electronics, classical analytical chemistry (chemical analysis) → modern analytical chemistry (mainly instrumental analysis) was realized

The third time: Since the 1970s, the application of computers, the arrival of the information age, and the improvement of basic theories and testing methods have promoted the entry of analytical chemistry. The third period of change

Concept: Substances that can be used to directly prepare standard solutions or calibration solutions with accurate concentrations

Requirements that reference materials should meet

Direct preparation method

Calibration method (indirect preparation method)

Advantages: simple and fast, can measure many elements and compounds, especially in the analysis of constant components. Because of its high accuracy, it is often used as a standard method.

Disadvantages: low sensitivity, poor selectivity, not suitable for analysis of trace components

The reaction must have a definite measurement relationship (the basis for quantitative calculations)

The reaction must be carried out quantitatively, that is, the degree of reaction must reach more than 99.9%

The reaction rate is faster

There must be an appropriate and simple method to determine the titration end point

It has good selectivity, coexisting substances do not interfere with the determination, or there is a suitable method to eliminate interference.

reaction type

Titration method

1. Collection, processing and decomposition of samples

2. Separation and enrichment of samples

3.Analysis and determination

4. Calculation and evaluation of analysis results

1. Chemical representation of the component to be measured

2. Expression method of content of components to be measured