Methods provided in this section must be used when a determination of moisture content in desiccated biological products is prescribed in an applicable Standard Requirement or in the filed Outline of Production for the product. Firms currently using methods other than those provided in this section for determining the moisture content in desiccated biological products have until November 5, 2004 to update their Outlines of Production to be in compliance with this requirement.

Final container samples of completed product shall be tested. The weight loss of the sample due to drying in a vacuum oven shall be determined. All procedures should be performed in an environment with a relative humidity less than 45 percent. The equipment necessary to perform the test is as follows:

Cylindrical weighing bottles with airtight glass stoppers.

Vacuum oven equipped with validated thermometer and thermostat. A suitable air-drying device should be attached to the inlet valve.

Balance, accurate to 0.1 mg (rated precision ±0.01mg).

Desiccator jar equipped with phosphorous pentoxide, silica gel, or equivalent.

Desiccated vaccine in original sealed vial. Sample and control should be kept at room temperature in their original airtight containers until use.

Test procedure:

Thoroughly cleaned and labeled sample-weighing bottles with stoppers should be allowed to dry at 60 ±3 °C under vacuum at less than 2.5 kPa.

Transfer hot bottles and stoppers into the desiccator and allow to cool to room temperature.

After bottles have cooled, insert stoppers and weigh and record the weights of the bottles as “A.”

Return weighing bottles to the desiccator.

Remove the sample container seal.

Using a spatula, break up the sample plug and transfer the required amount of sample to the previously tared weighing bottle.

Insert the stopper and weigh and record the weights of the weighing bottles as “B.”

Place the weighing bottle with the stopper at an angle in the vacuum oven. Set the vacuum to <2.5 kPa and the temperature to 60 ±3 °C.

After a minimum of 3 hours of drying time, turn off the vacuum pump and allow dry air to bleed into the oven until the pressure inside the oven is equalized with the prevailing atmospheric pressure.

While the bottle is still warm, replace the stopper in its normal position and transfer the weighing bottle to the desiccator.

Allow a minimum of 2 hours for the weighing bottle to cool to room temperature or for its weight to reach equilibrium.

Weigh, and record the weight as “C.”

Calculate the percentage of moisture in the original sample as follows:

The results are considered satisfactory if the percentage of residual moisture is less than or equal to the manufacturer's specification.