Moisture analysis

What is moisture?

Water is essential to life. It plays a critical role in the physical and chemical functions of our bodies, the food we eat, and the materials that surround us. In many industries it is important—if not critical—to measure the water content of substances to assess quality, adjust manufacturing processes, and ensure that products meet regulations and guidelines. The amount of available water dictates the shelf life and stability of many systems; for example, the presence of water in food greatly impacts its susceptibility to chemical, enzymatic, and microbial activity. 

moisture analysis balance ohaus

• Cosmetics
• Pharmaceuticals
• Food
• Personal care products
• Pulp and paper products
• Specialty chemicals

Measuring the amount of water contained in certain materials can be very difficult due to the complexity of the water molecule and its strong intermolecular bonding capabilities. In most cases, measurement of water is better defined as the measurement of moisture content, defined as the mass of water per unit mass of dry material. Thermogravimetric moisture analysis defines moisture as the loss of mass observed when the sample is heated and is based, in theory, on the vaporization of water during the drying process; this measurement does not distinguish weight loss of water from loss of volatile components or sample decomposition. For this reason, moisture content as measured by thermogravimetric techniques includes all substances which vaporize when heating a sample and are measured as weight loss during the heating process. Therefore, we use the term “moisture content” rather than “water content” when using a thermogravimetric device. 

What Is Thermogravimetric Moisture Analysis?

The moisture content influences the weight, density, viscosity, refractive index, and electrical conductivity of a material. Methods for testing moisture content tend to exploit one or more of these physical or chemical properties. Direct measurements address the presence of water itself, either through its removal or through chemical interaction. The use of a thermogravimetric moisture analyzer is a way to directly measure the moisture content of a sample by using the loss on drying (LOD) technique. LOD measures the weight of a sample before and after a drying procedure and uses the weight delta to determine the percentage of moisture as the weight removed by the drying process in comparison to the initial weight of the sample.

Typically, this process is done in a drying oven with a balance to determine the initial and final weight of the sample and using a simple mathematical calculation to determine the moisture content ([initial weight – end weight]/initial weight). This process typically takes several hours to complete and is vulnerable to user error. A moisture analyzer works on the same principle but is an automated system that employs a microprocessor-controlled heating element and an analyzer all in one device; by using such a device, the moisture content of a sample can be measured in minutes rather than hours.