GB/T 35924-2018 (English Version)

Standard No.: GB/T 35924-2018
Language: Chinese, Available in English version
Release Date: 2018
Published By: General Administration of Quality Supervision, Inspection and Quarantine of the People‘s Republic of China
Latest: GB/T 35924-2018

Scope: This standard specifies the thermogravimetric analysis method for the moisture content in solid chemical products. This standard is applicable to the determination of moisture content in solid chemical products with a moisture content range of 0.050% to 28.00%. This standard is not applicable to the determination of chemical products that are weathered, deliquescent, or volatile at room temperature, and chemical products with a decomposition temperature below 105°C. For some samples, the moisture content may include the amount of volatile matter below 105°C.

Introduction

Interpretation of the standard for determination of moisture content in solid chemical products

1. Background and significance of the standard

GB/T 35924—2018 "Determination of moisture content in solid chemical products - Thermogravimetric method" is the first standard in my country for the determination of moisture content in solid chemical products, filling the technical gap in this field in China. The standard is managed by the National Technical Committee for Chemical Standardization and is applicable to solid chemical products with a moisture content range of $0.050\%\sim28.00\%$.

2. Comparative analysis of standard frameworks

Standard dimensions	GB/T 35924—2018	International comparison (such as ISO/ASTM)
Scope of application	Solid chemical products, 0.05-28% moisture content	Applicable to a variety of materials, including food, medicine, plastics, etc.
Core methods	Thermogravimetric analysis (TGA)	Including weight loss method, Karl Fischer method, etc.
Instrument requirements	Thermogravimetric analyzer (in accordance with GB/T 27761)	Mostly use imported high-end TGA equipment

3. Technical principles and implementation points

Technical principle: Heat the sample through a thermogravimetric analyzer, record its mass change curve (thermogravimetric curve), and calculate the moisture content based on the weight loss. This method has the characteristics of high sensitivity and simple operation.

3.1 Experimental steps

Instrument preparation: Preheat to a stable state, adjust the inert gas flow rate to $50\mathrm{mL/min}\pm5\mathrm{mL}/\mathrm{min}$.
Blank determination: Measure the mass change of an empty crucible at high temperature.
Sample weighing: Accurately weigh $30~\mathrm{mg} \sim 40~\mathrm{mg}$ of sample and put it into the crucible.
Heating procedure: Heat up to $105^\circ\mathrm{C}$ at $10^\circ\mathrm{C}/\mathrm{min}$ and keep constant temperature until the weight loss rate is stable.

4. Implementation suggestions and precautions

Implementation suggestions:

Strictly control the experimental conditions to ensure that the heating rate and constant temperature time meet the standard requirements.
Choose appropriate crucible material to avoid reaction between the sample and the crucible.
Parallel test: Measure each sample at least twice and take the average value as the final result.

GB/T 35924-2018 Referenced Document

GB/T 27761 Standard test method of mass loss and residue measurement validation of thermogravimetric analyzers

GB/T 35924-2018 history

2018 GB/T 35924-2018 Determination of moisture in solid chemical products－Thermogravimetry method