What Is Moisture Analysis?

With the development of scientific research and the advancement of production technology, the quantitative analysis of moisture has been listed as one of the basic items of physical and chemical analysis of various substances as an important quality indicator of various substances.

According to the different moisture content in different types of samples, different requirements for measuring moisture are proposed. Moisture measurement can be either industrial control analysis or quality certification of industrial and agricultural products; moisture can be measured from tons of products or only a few microliters of test solution can be used for moisture analysis in the laboratory; A constant moisture analysis with a water content of a few percent to a few tens, but also a trace moisture analysis with a moisture content of less than one millionth.

These instruments are easy to operate, have high sensitivity and good reproducibility, and can continuously measure and automatically display data. The moisture measurement in foreign countries is expensive and cannot be afforded by some domestic laboratories and enterprises. It has strengthened the research and practice of moisture measurement, and achieved very obvious benefits, bringing the domestic moisture measurement technologies closer to international standards, which can meet the needs of general laboratories and enterprises. Classical moisture analysis methods have gradually been replaced by various moisture analysis methods.

Including: Karl Fischer moisture determination, Coulomb moisture determination, dew point moisture determination, etc.

I. Karl Fischer moisture determination:

The Karl Fischer method, referred to as the Fischer method, is a method of volume splitting for measuring water content proposed by Karl Fischer in 1935. The Fischer method is the most specific and accurate method for measuring the water content of various substances. After continuous improvement, the accuracy has been increased, the measurement range has been expanded, and it has been listed as the standard method for moisture determination in many substances.

2. Coulomb moisture determination:

Coulomb moisture analyzer is commonly used to determine the moisture content in a gas. This method is simple in operation and quick in response, and is especially suitable for the determination of trace moisture in gases. It is very difficult to measure by general chemical methods. However, the electrolytic method is not suitable for the determination of basic substances or conjugated diolefins.

3. Dew point moisture determination:

The dew point moisture analyzer is easy to operate, the instrument is not complicated, and the measured results are generally satisfactory. It is often used for the determination of trace moisture in permanent gases. However, this method has a lot of interference, and some easy-to-cold gas exchanges will cause condensation before water vapor, especially at higher concentrations.

Four. Microwave moisture meter determination:

Microwave moisture measurement uses a microwave field to dry the sample to speed up the drying process. It has the characteristics of short measurement time, convenient operation, high accuracy, and wide range of applications. It is suitable for grains, paper, wood, textiles, and chemical products. Moisture measurement in solid and viscous solid samples can also be applied to the determination of moisture in petroleum, kerosene and other liquid samples.

V. Infrared moisture measurement:

Infrared heating mechanism: When far infrared radiation is radiated to an object, absorption, reflection and transmission can occur. However, not all molecules can absorb far-infrared rays. Only polar molecules that show electricity can work. Water, organic substances and high-molecular substances have a strong ability to absorb far infrared rays. When these substances absorb far-infrared radiation energy and make their molecules, the frequency of the inherent vibration and rotation of atoms is consistent with the frequency of far-infrared radiation, it is extremely easy for resonance or rotation of molecules and atoms to occur, resulting in greatly intensified motion, which is converted into The thermal energy increases the temperature inside, so that the material is quickly softened or dried.

Model: ZDJ-3S Country of Origin:

Methods for measuring soil moisture include drying method, neutron method, TDR, FDR, resistance method, capacitance method, remote sensing method, ground exploration radar and so on. ^[1]

Moisture is a commonly used test item for drugs, and is often used in the inspection of drug substances or their preparations. It has a wide range of applications in the field of drug testing and has been widely included in pharmacopoeias in various countries. The level of moisture testing performed by the testing laboratory can objectively and more representatively reflect the drug testing capability of the laboratory. There are many influential factors in the determination of water in pharmaceuticals, such as the effect of the titer of the calibration solution of the Fischer's test solution, the effect of the solvent amount and the dissolution time, the effect of the weighing amount, and the effect of the titration instrument. .

Proficiency testing is an important part of the laboratory quality assurance system. Participation in proficiency testing activities is an important means to evaluate the level of laboratory testing, exercise the technical capabilities of personnel, and promote laboratory accreditation and international exchanges. In China, the national accreditation system for testing and calibration laboratories has made clear requirements for laboratories to participate in proficiency testing and obtain satisfactory results.

This study can organize participating laboratories to understand the overall level of domestic pharmaceuticals and other related testing areas by organizing a proficiency testing program for moisture determination in pharmaceuticals, and provide information for the management of these areas and the accreditation of CNAS; it can also enable participating laboratories to identify The differences between laboratories promote the common improvement of laboratories; CNAS can also identify, analyze, and solve problems through monitoring, and monitor the maintenance of accredited laboratories' testing capabilities. For the detection method, refer to Appendix M of the 2010 edition of the Chinese Pharmacopoeia, the first method (Fisher's method), and A (volumetric titration method) of "Moisture Determination Method" to measure water content.

In view of the requirements for the quality control of pharmaceutical moisture, this study tested the pharmaceutical moisture determination capabilities of 166 domestic pharmaceutical and veterinary testing agencies, and studied the sample preparation, uniformity and stability, results statistics, and capacity evaluation of the moisture determination capability verification. And discuss the test results ^[2] .