Discover the essential guide to the General Test Procedure for Loss on Drying (LOD) as outlined by the USP, BP, and IP Pharmacopoeia. This comprehensive article provides a detailed overview of the methodologies and standards required for accurate moisture content determination in pharmaceutical products.

Loss on Drying Test Procedure As per USP,BP, & IP

1.0     Objective

• • The objective of this General Test Procedure (GTP) is to describe the procedure to be used for performing loss on drying test (LOD).

2.0     Principle/Reaction

• • Loss on drying (LOD) is the loss in weight in % w/w resulting from water and volatile matter of any kind that can be driven off under specified conditions.

3.0     Requirements: As per IP/USP/BP/Ph.Eur.

• • Phosphorous Pentoxide – A white, amorphous, deliquescent powder hydrated by water with the evolution of heat. Store in an air tight container.
  • A clean and dry glass stoppered bottle

• • Vacuum oven

• • Vacuum desiccator

4.0   Test Procedure of Loss on Drying (LOD)

• Loss on Drying (LOD) procedure as per United States Pharmacopoeia (USP)

  • Conduct the determination on 1 or 2 g if the test specimen is in the form of large crystals, reduce the particle size to about 2 mm by quickly been dried for 30 minutes under the same conditions to be employed in the determination.

• • Put the test specimen in the bottle, replace the cover, and accurately weigh the bottle and the contents.

• • By gentle sidewise shaking, distribute the tests specimen as evenly as practicable to a depth of about 5 mm generally and not more than 10 mm in the case of bulky material.

• • Place the loaded bottle in the drying chamber, removing the stopper and leave it also in the chamber.

• • Dry the test specimen at the temperature and for the time specified in the standard test procedure.

• • The temperature specified in the monograph is to be regarded as being within the range of ±2ºC of the stated value.

• • Upon opening the chamber, close bottle promptly, and allow it to come to room temperature in a desiccator before weighing.

• • If the substance melts at a lower temperature, maintain the bottle with its contents for 1 to 2 hours at a temperature 5ºC to 10ºC below the melting temperature, then dry at the specified temperature.

• • For capsules: Use a portion of the mixed contents of not fewer than 4 capsules.

• • For Tablets: Use powder from not fewer than 4 tablets ground to a fine powder.

• • Where drying in vacuum over a desiccant is directed in the standard test procedure, a vacuum desiccator or a vacuum drying pistol, or other suitable vacuum drying apparatus, is to be used. 

• • Where drying in a desiccator is specified, exercise particular care to ensure that the desiccant is fully effective by frequent replacement/regeneration.

• • When drying in capillary-stoppered bottle in vacuum is directed in the standard test procedure, use a bottle or tube fitted with a stopper having a 225 ± 25 µm diameter capillary and maintain the heating chamber at a pressure of 5 mm or less of mercury.

• • At the end of the heating period, admit dry air to the heating chamber, remove the bottle, and with the capillary stopper still in place allow it to cool in a desiccator before weighing.

• Loss on Drying (LOD) procedure as per British Pharmacopoeia/Ph. Eur.

  • Place the prescribed quantity of the substance to be examined in a weighing bottle previously dried under the conditions prescribed for the substance to be examined.

• • Dry the substance to constant mass or for the prescribed time by one of the following procedures.

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

• • “In a desiccator”: the drying is carried out over Di-phosphorus Pentoxide R at atmospheric pressure and at room temperature.

• • “In vacuo”: the drying is carried out over Di-phosphorus Pentoxide R, at a pressure of 1.5 kPa to 2.5 kPa at room temperature.

• • “In an oven within a specified temperature range”: the drying is carried out in an oven within the temperature range prescribed in the standard test procedure.

• • “Under high vacuum”: the drying is carried out over Di-phosphorus Pentoxide R at a pressure not exceeding 0.1 kPa, at the temperature prescribed in the standard test procedure.

• • If other conditions are prescribed, the procedure to be used is described in full in the standard test procedure.

• Loss on Drying (LOD) procedure as per Indian Pharmacopoeia (IP)

  • Place the prescribed quantity of the substance to be examined in a weighing bottle previously dried under the conditions prescribed for the substance to be examined.

• • Transfer to he bottle the quantity of the sample specified in the individual monograph, cover it and accurately weigh the bottle and the contents.   

• • Distribute the sample as evenly as practicable by gentle sidewise shaking to a depth not exceeding 10mm.

• • place the loaded bottle in the drying chamber (oven or desiccator) as directed in the monograph, remove the stopper and leave it also I the chamber.

• • Dry the sample to constant weight or for the specified time and at the temperature indicated in the monograph. After drying is completed, open the drying chamber, close the bottle promptly and allow it to cool to room temperature (where applicable) in a desiccator before weighing.

• • Weigh the bottle and the contents.

• • NOTE – Where drying in a desiccator is specified, care must be taken to keep the desiccant fully effective by frequent replacement. (2) Where the drying temperature is indicating by a single value, dry at a prescribed temperature ±2ºC.  

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