Loss on Drying (LOD) Practice Flashcards

A set of vocabulary flashcards covering the definition, principle, procedure, calculation, and pharmacopeial limits for Loss on Drying (LOD).

Loss on Drying (LOD)

The loss in mass expressed as a percentage, caused by the removal of moisture and other volatile matter by drying a substance under the specified conditions.

LOD Principle

A sample is heated at a specified temperature for a specified time to drive off moisture and volatile substances; the decrease in weight is measured and expressed as a percentage.

$$W_0$$

The weight of the empty moisture dish with lid expressed in grams ($g$).

$$W_1$$

The weight of the moisture dish and lid plus the sample before drying expressed in grams ($g$).

$$W_2$$

The weight of the moisture dish and lid plus the sample after drying expressed in grams ($g$).

Constant Weight

The endpoint of drying where the difference between two consecutive weighings is NMT $0.5\,mg$.

LOD Formula (% w/w)

$$\frac{W_1 - W_2}{W_1 - W_0} \times 100$$

Standard LOD Temperature

$105\,^\circ\text{C}$ (unless otherwise specified in the monograph).

Standard LOD Atmosphere

Air.

LOD vs. ROI (Measurement)

LOD measures the loss of moisture and volatile matter, while ROI (Residue on Ignition) measures inorganic residue (ash) remaining after ignition.

Typical ROI Temperature

Ignition at $550-600\,^\circ\text{C}$.

USP Typical LOD Limit

NMT $0.5\% - 10\%\,w/w$, though it varies by individual monograph.

BP Typical LOD Limit

NMT $0.5\% - 5\%\,w/w$, though it varies by individual monograph.

Ph. Eur. Typical LOD Limit

NMT $0.2\% - 5\%\,w/w$, though it varies by individual monograph.

Types of Volatile Matter

Includes water (moisture), solvents, alcohols, and other volatile organic compounds.

Desiccator

Equipment used during the cooling phase of the LOD procedure to avoid moisture uptake by the sample.