Loss on drying is described as the weight loss as a w/w percentage resulting from volatiles and water of any kind that can be removed under specified conditions. This test is performed on a mixture of substances. If the substance to be tested is in the form of large particles, then the sizes should be reduced by rapid crushing to a powder. The test consists of determining the content of water and volatile substance in a sample that is exposed to heat. Loss on drying is a technique that has been used for many pharmaceuticals. There are different methods to carry out this test and the technician chooses the most appropriate depending on the substance to be tested.
To perform the test, do the following:
Weigh a shallow weighing bottle that has been dried under the same conditions that will be used in the determination.
Transfer to the dry bottle the amount of sample specified in the individual monograph.
Cap the bottle and accurately weigh it and its contents.
· Distribute the sample evenly by gently shaking from side to side to a depth not exceeding 10 mm.
Dry the substance by placing the bottle in the drying chamber
· Remove the cap and leave it in the chamber.
· Dry the sample until constant weight.
· Open the drying chamber and quickly close the bottle and let it cool to room temperature.
Weigh the bottle and its contents.
The temperature to which the substance to be tested must be exposed is always specified and must not be exceeded so as not to obtain erroneous results. Each substance has its specific heat level.
The loss on drying test in pharmaceuticals is a technique for removing water and other volatile impurities from a sample of a well-mixed substance. the amount of heat applied to the substance depends on time and temperature.
The total moisture content of pharmaceuticals can contain both free and bound water.
Where impurities are present, the loss in dryness level will be greater compared to the water content.
Sometimes the loss on drying level can be much less compared to the water content, as some water molecules may not be removed by heating as in other methods of determining loss on drying. To calculate the percentage loss on drying, the method is shown below.
Percentage LOD = Percentage Water Content – Percentage of water molecules in the API
The type of substance that is being used must be known, the prescription must be known exactly to determine how the experiment is carried out. For the hydrated substance, the equivalent weight of the anhydrous content must be calculated before being exposed to heat. In case moisture is specified in the certificate, the pharmacy before using the substance in the loss on drying experiment.
Conclusion
Loss on drying has been used by many pharmaceutical companies to determine the concentration of drugs. These experiments are used to perform tests to also determine the substances present in moisture. This experiment requires great care and keenness if true results are to be found. The weight must be measured with non-defective devices to ensure that the wait is accurate. During heating, it must be completed to ensure that there is water left.