Learning Objective

• Quality check of propellants, containers and valve assembly

The propellants meant to be used in pharmaceutical aerosols should undergo rigid quality control tests. In general, all propellants require special handling procedures and test procedures. A sample propellant is sent to the laboratory to determine its identity by gas chromatography. When a blend of propellant is present, then the composition is estimated and the vapor pressure and density are determined. The propellant’s purity is determined by estimating the moisture, halogen and non-volatile residues.

The quality control of valves is a complex process since it is not made of single component. The valves, actuators and dip tubes are subjected to both physical and chemical inspection. The different valve components are assembled in order that the valve performs its function. The examination of valves is to determine whether the valves are fit to be used. The valve is tested to determine the magnitude of valve delivery and the uniformity.

The quality control of aerosol containers depends on the material. Coated and uncoated metal containers are examined for defects in lining. Degree of conductivity determines the amount of exposed metal. Glass containers are examined for flaws. The dimensions of the neck and other parts must be checked to determine conformity to the specifications.

Weight checking is done on empty containers, after filling with the product concentrate and after adding the propellant. When propellant blend is used then checks are carried out to determine the proper blend.

Leak testing of the containers is carried out by passing the final filled container through water baths. The temperature of the water baths is periodically checked and recorded.

Spray testing is carried out on all pharmaceutical aerosols. This clears the dip tube of all propellants (for products filled via process of pressure filling), to clear the dip tube of pure concentrate for products filled by pressure under the cap or around the stem. The spray test helps to detect the defects in the valve. The test primes the valves of metered-dose products such that the products are ready to be used by the consumer.