HELOS/BR
SPRAYER
ROTOR

Droplet size analysis of pharmaceutical nasal sprays in different spatial orientations with laser diffraction from 0.25 µm to 875 µm

Together with the flexible SPRAYER adapter, the compact laser diffraction sensor HELOS/BR offers meaningful and reproducible analysis of the size distribution of droplets in nasal and pharyngeal pump sprays in the range from 0.25 µm to 875 µm. The system can be flexibly adapted for a wide range of different atomizer types and simulates the manual application of the relevant spray with a force and trajectory release with the actuator SMACTOR. In combination with the ROTOR, it is possible to set up tilted application arrangements.

The formation of a spray mist depends on many different parameters. These need to be taken into account and controlled when setting up reproducible measuring conditions. Important actuation parameters include e.g. the force and displacement conditions when the atomizer is used. Likewise, the distance and orientation of the spray in relation to the measuring zone also have an influence on the measurement results. A suction unit ensures that laminar flow conditions are established in the measuring zone and that the spray mist is purged out. The key measurement and actuation parameters can be controlled in the HELOS & SPRAYER system with the software and stored as retrievable measuring methods (Standard Operating Procedures (SOPs)).

The intelligent trajectory and force actuator SMACTOR is available for the SPRAYER for simulation of individual thumb pressures and actuation processes. The force mode ensures the actuation of the spray process by the actuator piston operating the pump or valve mechanism with a predefined force progression. In trajectory mode, the atomiser is actuated via a movement path of the actuator piston, which is defined on the basis of stroke, acceleration and maximum velocity. A profile mode allows path/time profiles to be stored. The predefined profile is run during the next spray stroke. The use of controlled actuation processes helps to establish reproducible measuring methods and avoids unwanted operator bias.

For spatial orientation of the spray and the pump device, the complete HELOS & SPRAYER system is mounted in the traversing unit ROTOR, which lifts up the system and allows for rotation in increments of 5° to the desired tilt angle between 0° and 90°. A sensor integrated in the SPRAYER  records the tilt angle.

For reliable identification of the different spray phases (formation, stable phase, dissipation), a time-resolved measurement of the generated spray mist is performed with up to 2,000 particle size distributions per second. Identification of the stable phase of spray formation forms the basis for the reproducibility of subsequent measurements in the fully developed droplet cloud. Force, velocity and stroke of the actuation process are recorded by the software and displayed in diagrams.

Temporally segmented measurements allow a subsequent identification of the different development phases of the spray. A summary of segments allows the stable phase to be evaluated retrospectively for the evaluation. Advantages arise, for example, with single-use devices or temporally varying progressions of spray phases of a spray. The selection and evaluation of the stable phase is carried out directly via the segmentation of the measurement just performed. A new measurement is not necessary. Reports and diagrams document and visualise, in addition to the droplet size distribution, the temporal course of all data of the measurement as well as the currently made segment selection on which the result is based.

The system creates the best conditions for compliance with the requirements of regulatory authorities for pharmaceutical products, e.g. the guidelines of the US FDA (Food and Drug Administration). HELOS & SPRAYER are used both for fundamental research applications and in product development, as well as in quality control.