Procedure For Loss On Ignition (LOI)

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What is the Principle of Loss On Ignition (LOI)?

The Loss on Ignition test is a procedure to determine the processing of the material that is volatilized and driven off under the conditions specified.

This method is usually applied to inorganic drugs which lose a part of the components or impurities during ignition. The ROI results is expressed in % w/w.

How to perform Loss on Ignition (LOI)?

  1. Take a suitable crucible, (Silica, Platinum, Quartz, and Porcelain) with a lid, unless other equipment is designated in the individual STP.
  2. Conduct the ignition in a suitable muffle furnace or oven at a specified temperature for 1 hour.
  3. Allow cooling in a desiccator over (Silica gel or another suitable desiccant) and accurately weigh (W1 in gm).
  4. The test is to be performed on finely powdered material, and break up lumps, if necessary with the aid of a mortar and pestle before weighing the sample.
  5. Weigh the sample to be tested into the crucible without further treatment, unless a preliminary drying at a lower temperature, or another special pretreatment, is specified in the current individual STP.
  6. Unless otherwise directed in the individual STP, 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:
  7. Formula: 10/L
    • Where, L= limit (or the mean value of the limits) for Loss on ignition, in percentage.
  8. Take the weight of the crucible with the sample accurately (W2 in gm).
  9. Ignite the loaded uncovered crucible, and cover at the temperature (+/- 25°C) and for the period of time designated in the individual STP.
  10. Ignite for successive 1-hour periods where ignition to constant weights is indicated.
  11. Until 2 consecutive weights do not differ by more than 0.5mg/g of the specimen.
  12. Upon completion of each ignition, cover the crucible, and allow it to cool in a desiccator to room temperature and weigh accurately (Wf in gm).

The calculation formula of Loss on Ignition:

% Loss on Ignition = (W2-Wf) x 100 / (W2-W1)

Where, Wf is the final weight of the crucible.

Loss on Ignition
Loss on Ignition

References:

ReferenceGeneral Chapter
USP<731> Loss on Ignition
IP2.4.20 Loss on Ignition
JP2.43 Loss on Ignition.

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