Introduction
Moisture analysis is determining moisture content within a sample material. Many analytical techniques are useful for moisture analysis, and the choice depends on sample type, accuracy required, and available resources.
Karl Fischer Titration
Karl Fischer titration (KFT) determines moisture content through a chemical reaction. A solution with known water content is added to the sample until the Karl Fischer endpoint is reached, indicating a water-free state. The amount of solution added directly relates to the moisture content in the sample.
Loss on Drying
Loss on drying (LOD) involves drying a sample at a specific temperature and measuring the weight loss. A drying oven or vacuum oven is typically used, and drying conditions (temperature, time, pressure) depend on the material’s properties.
Microwave Moisture Analyzer
Microwave moisture analyzers use microwaves to heat and evaporate moisture from a sample. The weight loss is monitored continuously, and the moisture content is calculated automatically.
Coulometric Karl Fischer Titration
Coulometric Karl Fischer titration (CKFT) is an extension of KFT that electrolytically generates iodine instead of using a pre-prepared solution. This allows for more precise and automated moisture determination.
Gas Chromatography
Gas chromatography (GC) can separate and quantify moisture content based on the different boiling points of the components in a sample. Specialized columns and detectors are required for moisture analysis using GC.
Hygroscopy
Hygroscopy is a method that measures the amount of moisture absorbed or desorbed by a material under controlled conditions. The material’s weight change is monitored to determine the moisture content.
Other Techniques
- Near-infrared spectroscopy (NIRS)
- Nuclear magnetic resonance (NMR)
- Vapor sorption analysis
Choosing the Right Technique
Selecting the appropriate moisture analysis technique relies on the following factors:
- Material properties
- Moisture content range
- Accuracy and precision requirements
- Availability of equipment
- Cost and time constraints