Loss on drying

Why loss on drying is performed in pharmaceuticals | Loss on drying procedure |

Loss on drying (LOD) is a common test method used in various industries, including food, pharmaceuticals, and manufacturing, to determine the moisture content of a material.

The loss on drying test is performed in pharmaceuticals to measure the amount of water and volatile substances present in a sample.

Loss on drying (LOD) is determined by heating the sample below its melting point in an oven and it includes all volatile matter including water content and solvents.

Pharmaceutical importance of loss on drying: LOD testing is essential in quality control, as excessive moisture or volatile content in a product can impact its quality, stability, shelf life, and processing characteristics. The method typically involves heating the sample in an oven at a specific temperature for a specified period to ensure consistent results.

The test is carried out on a well-mixed sample of the substance. If the substance is in the form of large crystals, reduce the size by rapid crushing to a powder.

Where the drying temperature is indicated by a single value other than a range, drying is carried out at the prescribed temperature ± 2°.

Loss on drying procedure: Weigh a glass stoppered, shallow weighing bottle that has been previously dried under the same condition to be employed in the determination, & cooled. Note down the weight as W1. Place 1 gm or specified in monograph of the sample in weighing bottle, cover with the lid & accurately weigh the bottle and the contents. Note down the weight as W2. Distribute the sample as evenly as practicable by gentle sidewise shaking to a depth not exceeding 10 mm.

Place the loaded bottle in the drying oven by removing the stopper and leave it also in the oven. Dry the sample to constant weight for specified time. After drying is completed, open the drying oven, close the bottle promptly and allow it to cool to room temperature (where applicable) in a desiccator. Weigh the bottle and note down the weight as W3. Calculate the loss on drying by the equation :   

                                                       W2 – W3

              % Loss on drying      =   —————- x 100

                                                         W2 – W1

Dry the sample again by following the same drying procedure and same condition for 30 minutes, the difference between two consecutive weighing should not be more than 0.50 mg per gm of the sample taken.

Acceptance Criteria: Specified in monograph