Device design nebulisers

Basically four different types of commercially available aerosol generation devices exist dry powder inhalers (DPIs), metered-dose inhalers (MDIs), classic jet and ultrasonic nebulisers and a new class of high-performance liquid inhalers. Each of these categories has many different variations of the same basic design and working principle... 

When a nasal spray is supplied in a squeeze bottle instead of one with a pump atomizer, a viscous spray might be difficult to nebulise. So, in the design of a spray formulation, viscosity has to be considered together with the intended type of container and atomising device. 

In order to overcome drawback 1 several nebulisers and spray chambers have been developed. In this field, considerable effort has been dedicated to the design of new pneumatic devices able to efficiently take advantage of the gas kinetic energy. To solve drawback 2, two general choices are available (i) pneumatic concentric nebulisers with modified critical dimensions and (ii) pneumatic nebulisers in which the geometry of the liquid and gas interaction is not concentric. Other non-pneumatic nebulisers have also been designed that overcome either or both of these drawbacks. 

Thermal, or thermospray, nebulisers also improve sensitivity. With these nebulisers, the sample goes through a narrow, heated capillary. A fraction of the solvent evaporates and the aerosol is generated as the vapour expands at the exit of the capillary. The thermospray device provides similar analytical figures of merit as the ultrasonic nebuliser and it also requires a system for solvent removal. Furthermore, the capillary is easily blocked, so the tolerance of this nebuliser design to dissolved solids is limited. 

A pneumatic cross-flow micronebuliser has been described for use in ICP-MS. The high efficiency cross-flow micronebuliser (HECFMN) has a narrow capillary placed inside the conventional sample capillary. The inner diameter of the nebuliser gas nozzle is reduced with respect to the conventional cross-flow design. Due to the characteristics of this device, the free liquid uptake rate (i.e. about 9 p-L/min) is lower than that found for either a conventional cross-flow nebuliser (i.e. 1900 pL/min) or concentric pneumatic micronebulisers (i.e. from about 30 to 100 pL/min). This fact makes the HECFMN attractive for CE ICP-MS interfaces. ... 

---