LOSS ON IGNITION
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This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition
Issued and maintained by the United States Pharmacopeial Convention (USP)
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This procedure is provided for the purpose of determining the percentage of test material that is volatilized and driven off under the conditions specified.
Perform the test on finely powdered material, and break up lumps, if necessary, with the aid of a mortar and pestle before weighing the specimen. Weigh the specimen to be tested without further treatment, unless a preliminary drying at a lower temperature, or other special pretreatment, is specified in the individual monograph. Unless other equipment is designated in the individual monograph, conduct the ignition in a suitable muffle furnace or oven that is capable of maintaining a temperature within 25° of that required for the test, and use a suitable crucible, complete with cover, previously ignited for 1 h at the temperature specified for the test, cooled in a desiccator, and accurately weighed.
Unless otherwise directed in the individual monograph, transfer to the tared crucible an accurately weighed quantity, in g, of the substance to be tested, about equal to that calculated by the formula:
10/L
in which L is the limit (or the mean value of the limits) for Loss on Ignition, in percentage. Ignite the loaded uncovered crucible, and cover at the temperature (±25°) and for the period of time designated in the individual monograph. When "ignition to constant weight" is specified in a monograph, ignite for successive 1-h periods until two consecutive weighings do not differ by more than 0.50 mg/g of specimen. Upon completion of each ignition, cover the crucible, and allow it to cool in a desiccator to room temperature erature before weighing accurately (ERR 1-Nov 2020).
