HELOS/BR
SPRAYER

Laser diffraction analysis of pharmaceutical pump sprays with droplets 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 or trajectory mode.

The formation of a spray mist depends on many different parameters, and these need to be taken into account and controlled when setting up reproducible measuring conditions. Important actuation parameters include e.g. the force and acceleration 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, as well as the distance of the spray nozzle from the measurement zone, can be controlled in the HELOS & SPRAYER system with the software and saved as retrievable measurement methods (Standard Operating Procedures (SOPs)).

For the simulation of different manual thumb and actuation processes, the intelligent actuator SMACTOR is available in the SPRAYER in force, trajectory or profile mode. The force mode ensures that the spray is actuated with a definable, constant maximum force and its rise time by pushing the actuator piston onto the actuation mechanism. In the trajectory mode, the atomizer can be actuated with a motion path for the actuator piston that is defined by the travel (stroke), acceleration and maximum velocity. A profile mode allows more complex travel/time profiles to be stored. The predefined profile is run during the next spray stroke. The use of controlled actuation processes by the actuator not only supports the establishment of reproducible measurement methods, but also enables the investigation of any undesirable user influences.

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. The identification of the stable phase of spray formation forms the basis for the reproducibility of subsequent measurements in the fully developed droplet cloud. The force, velocity and stroke of the actuation process are recorded by the software and can be displayed in different 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 of a spray is carried out directly via the segmentation of the measurement just performed. A new measurement is therefore 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 accordingly both for fundamental research applications and in product development, as well as in quality control.