Density measurement for inhalant supervision

Hydrofluoroalkanes (HFAs) are used for pharmaceutical and medicinal purposes, especially as aerosol propellants in inhalers. With a suitable medical excipient added, HFAs can serve as drugs for the treatment of human respiratory diseases. Density measurement allows determining the correct compositions.

1 General aspects

Hydrofluoroalkanes (HFA) are gaseous components composed of carbon, fluorine, and hydrogen. These components are inert in the human airway, and do not contribute to depletion of the stratospheric ozone layer.

A representative of the family of HFAs is 1,1,1,2,3,3,3-Heptafluorpropane (HFC-227; trade name Solkane® 227 or Solkaflam® 227 by Solvay). Its molecular formula is C3HF7.

With a suitable medical excipient added, HFC sprays allow administering drugs in an efficient way, and are also easy to handle for patients.

The correct dosage of excipient is crucial for optimum treatment. The question arose whether the concentration of an excipient can be determined by density measurement thus making the density of the mixture a method for reliable quality control.

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