Loss on Drying (LOD) for Volatile Content Monitoring

In many cases, for a range of products and raw materials, the moisture content of a substance must be accurately determined in order to establish the quality of a standard specification. From chemicals to pharmaceutical preparations to food products, moisture content is critical to the shelf life of raw materials and products and trace amounts of moisture must be carefully controlled. Substances to be used in prescriptions must not only be free of impurities, but also be measured with precision. The nature of all involved substances must be known exactly. As a routine testing method in the pharmaceutical industry, knowing the moisture content of your materials is important for quality control as well as health and safety protection. Loss on drying, or LOD, is a common method used to determine moisture content. Moisture refers to all substances in a sample that can be vaporized, and therefore includes not only water, but also fats, volatile solvents and alcohols.

Equipped with state-of-the-art moisture analysis technology, BOC Sciences wet chemical analysis laboratory is able to provide a complete range of test parameters. Our LOD test can be used to determine the amount of volatiles present in tablets, capsules or bulk materials, which helps to speed up the turnaround time for samples that are frequently tested under the same conditions.

Principles of LOD

The LOD method is developed based on the thermogravimetric principle, where a substance is heated until it no longer loses weight. The weight of the substance is measured at the beginning and after reaching the dry state. And the final weight loss is calculated and represents the moisture content of the sample.

Our Methods

LOD is important since high moisture lead to sticking, inappropriate flow of blend, while low moisture lead to low hardness, friability ,capping and lamination. At BOC Sciences, several wet chemistry techniques are used to achieve moisture vaporization, including drying chambers heated by gas, and ovens that work by infrared or microwave radiation.

Drying Ovens

We place the tested sample in a drying oven and then repeatedly weigh it according to a preset schedule and record the weight loss. Once the weight remains constant, the percentage of moisture in the pharmaceutical formulation is quantified by calculating the difference between the initial weight and the final weight.

Microwave Drying

Microwave heating and vaporization of the moisture in the sample is extremely fast, taking only a few minutes. In addition, the size of the sample does not have to be very small.

Infrared Drying

We offer infrared heating technology for finding the moisture content of samples, but only for small samples weighing 0.1 to 120 grams. For small samples, this determination takes little time and the weight loss measurement can be used to automatically calculate the moisture lost from the sample.

Moisture analyzer

Prior to heating, the sample is first weighed accurately. The heating temperature is usually kept below the melting point and below the degradation point. The drying time is much shorter compared to a conventional convection drying oven. Once the process starts, the sample is automatically weighed and the weight is repeatedly recorded. When a constant state is reached, the balance is turned off. The device then finds the final weight loss and uses it to determine the moisture content of the sample.

Figure 1. Loss on drying and response to applied stress. (Al-Tabakha, M. M.; et al. 2015)

Advantages of Our LOD Services

• High accuracy and repeatability
• Real-time moisture curves and drying rate graphs
• More detailed analysis if needed
• Recommend the best testing strategy for your pharmaceutical raw materials according to their applications