A technique is described for producing monodisperse (geometric standard deviation, σ g, < 1.2) labelled particles of low solubility, needed for experiments on the long term kinetics of clearance of particles from the respiratory tract. Montmorillonite clay in aqueous suspension is labelled with an appropriate radionuclide by ion exchange. An air driven spinning top is used to produce monodisperse droplets of the clay suspension, which are dried, concentrated into a comparatively small air flow and heated to 1200°C. The clay melts and on cooling forms a glass in which the label is trapped. Monodisperse particles in the size range 1-5 μm can be produced with a yield greater than 10%. The system is relatively inexpensive and is equally suited to producing particles of other materials which require heat treatment in their preparation.
Bibliographical noteFunding Information:
Acknowledgements--This work was carried out with partial support from the CEC under Contract 182-76-2 BIO UK. The authors wish to thank Dr. A. C. James for his advice and encouragement, Mrs. M. A. Byrne, Miss J. E. Hostford and Miss A. J. Savory for technical assistance and Drs O. G. Raabe and M. Hoover of the Inhalation Toxicology Research Institute, Albuquerque, who kindly provided samples of montmorillonite clay.