Nitrogen aerosol propellant

A number of compressed and liquified gases are used as refrigerants and aerosol propellants. These include nitrous oxide, nitrogen, carbon dioxide, propane, and butane. The use of chlorofluorocarbons (CFCs) is restricted because of environmental pollution leading to health hazards. These have been replaced by hydrogenated fluorocarbons (HFCs), which are less likely to cause environmental pollution. 

Propellants. The propellant, said to be the heart of an aerosol system, maintains a suitable pressure within the container and expels the product once the valve is opened. Propellants may be either a Hquefied halocarbon, hydrocarbon, or halocarbon—hydrocarbon blend, or a compressed gas such as carbon dioxide (qv), nitrogen (qv), or nitrous oxide. 

Aerosols used for inhalation therapy are generally packaged in containers with metered values. The standard procedure is to discharge the entire contents of the container for assay. For betamethasone dipropionate and betamethasone valerate topical aerosols, the contents are discharged into a volumetric flask and the propellants carefully boiled off. Precautions should be taken, as many of these propellants are flammable. The residue is diluted to volume with isopropanol-acetic acid (1000 1) and filtered [50]. Another approach is to discharge the contents into ethanol or dilute acid. An alternative is to immerse the canister in liquid nitrogen for 20 min, open the canister, evaporate the liquid contents, and dissolve the residue in dichloromethane. A unit spray sampling apparatus for pressurized metered inhalers has been described [51]. The components in an aerosol product that can be the cause of assay variance have been studied [52]. A method to quantify the volatile components of aerosol products has been developed [53]. 

Carbon dioxide and other compressed gases such as nitrogen and nitrous oxide are used as propellants for topical pharmaceutical aerosols. They are also used in other aerosol products that work satisfactorily with the coarse aerosol spray that is produced with compressed gases, e.g., cosmetics, furniture polish, and window cleaners. ... 

There is another class of aerosols, known as single phase aerosols, in which the propellant is a compressed inert gas, for example carbon dioxide, nitrogen and nitrous oxide. With this type of pack a high pressure is used initially (90-150 lb/in2) since the internal pressure diminishes as the container is emptied. A single phase aerosol is more acceptable as a foam dispenser for toothpaste and hand cream than a spray pack, but if used inverted all the gas will be released quickly (unless it is specifically designed to be used inverted) and the product will remain with no means of dispensing it. 

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