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3M Drug Delivery Systems
An Evaluation of Analytical Techniques for Characterising the Plume Velocity and
the Plume Force of Pulmonary and Nasal Products
Chris Blatchford & Gemma Nixon, 3M Drug Delivery Systems, Morley St, Loughborough, UK .
Graham Hargrave, Tim Justham & Edward Long, Wolfson School of Mechanical and Manufacturing Engineering, Loughborough University, UK . .
Introduction
The pMDI units were held at an angle so that the plume had a horizontal trajectory.
The data from three selected pMDI products also show that measurements can be
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whole poster
Two analytical techniques, high speed laser imaging and plume force
The actuation was triggered by a solenoid valve with a compressed air supply held at
taken at different distances and there is obvious consistency of the data at the
60psi. The trigger was also synchronised to start the video camera. The high
different distances (Figure 4).
measurements have been investigated for measuring the ex-actuator plume from
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pulmonary and nasal products. The advantages and disadvantages of the
resolution images were transferred to a PC and the digital data manipulated using
techniques are discussed with an analysis of data from a range of marketed
products.
The Leading edge velocity data gives a better indication of the way the plumes from
specifically designed in-house software.
different pMDI products dissipate with distance (Figure 5). Some devices have
Software algorithms were set up to follow the leading edge of the ex-actuator plume
plumes with leading edge velocities of more than 20 msec-1 when close to the
over the first 10 cm and the distance/time data was converted into distance/velocity
actuator but at a distance of 5 cm these have typically reduced to below 15 msec-1.
data as shown in Figure 5.
Product B has consistently lower plume force and leading edge velocity between 3
and 7 cm firing distance, whereas Product C has the highest force and the highest
Spray Force Experimental
leading edge velocity.
Results
The Copley Scientific SFT1000 Spray Force Tester has an integrated Mecmesin
AFG 2.5N Force sensor which records the spray force from the evolved plume.
During initial testing it was found there was mechanical interference both actuating
the unit and pressing the tare button on the force sensor. The instrument was used
The spray force data showed that there was a very high range of forces for different
Leading Edge Velocity at distance from actuator - High Speed Laser Imaging
products and there was a large overlap in the plume forces for pMDI and nasal spray
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products (Figures 2 and 3).
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in a modified configuration with the force sensor and plate re-positioned so they
Boxplot of Maximum Spray Force (mN) vs Product
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Maximum Spray Force (mN)
shown in Figure 1.
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Velocity (m/s)
were facing in the opposite direction and the actuator held in a separate jig, as
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Conclusions
Product
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Distance (cm)
Product A
Product B
Product C
Figure 5 – Leading edge velocity by High Speed Laser Imaging for Products A, B
and C
Figure 2 – Spray Force of pMDI products
Conclusions
Boxplot of Maximum Spray Force (mN) vs Product
Leading edge velocity and spray force measurements are both useful analytical
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Maximum Spray Force (mN)
Figure 1 – Spray Force Tester Modified Set-Up
The Spray Force Tester can be set up in two modes, either to measure the
maximum force over the duration of the spray plume, or a high speed analogue
output. High speed analogue data capture showed that when a force was applied
to the plate there was a resonance set up in the sensor at about at about 1kHz.
This resonance interfered with the high frequency force of the plume and therefore
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on a wide range of commercially available inhalation products. The data from three
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pMDI products show that both plume force and leading edge velocity measurements
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have detected similar trends i.e. those plumes with a higher leading edge velocity
tend to have a higher spray force.
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Leading edge velocity measurements require sophisticated research equipment and
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all further studies were performed with the instrument in maximum force mode.
techniques for the characterisation of spray plumes and this has been demonstrated
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when the operator presses the buttons or actuates the MDI and from the resonance
products (Figure 2) and nasal spray products (Figure 3) at a firing distance of 5cm
using 3 shots from 3 devices for each product (n=9). Three pMDI products were
Scientific SFT1000 Spray Force Tester is much easier to use and is a less costly
option, however there were some imitations including the vibration of the instrument
Product
The equipment was used to analyse a wide range of commercially available pMDI
customised software which is not available as a commercial product. The Copley
frequency in the force sensor.
Figure 3 – Spray Force of nasal spray products
also measured at 3cm, 5cm and 7cm (Figure 4) for comparison with the leading
edge velocity experiments.
Acknowledgements and References
Peak Spray Force - Copley Scientific Spray Force Tester SFT1000.
(Error bars indicate data range)
The authors would like to thank Mark Copley for helpful discussions and for the loan
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A method was developed using a pulsed laser (20nsec pulse width) and a
synchronised high speed video camera to record images of the ex-actuator pMDI
plume at a frequency of 10kHz. The laser beam was configured as a vertical sheet of
light which passed through the ex-actuator plume in the opposite direction to the
plume trajectory. The plane of light was aligned slightly in front of the nozzle so that
any heating affects caused by the high intensity light source would not affect the
atomisation process or distort the actuator orifice. The video camera was focused
precisely on the laser light plane.
3M Drug Delivery Systems
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Peak Spray Force, mN
High Speed Laser Imaging Experimental
of a Copley SFT1000 Spray Force Tester
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Gabrio B, Stein S and Velasquez D.
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A New Method to Evaluate Plume
Characteristics of Hydrofluoroalkane and Chlorofluorocarbon Metered Dose Inhalers.
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International journal of Pharmaceutics, Volume 186, Issue 1, 10 September 1999,
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Pages 3-12.
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3 cm
5 cm
7 cm
Guo C and Doub W. Development of a Novel Technology to Measure impaction
Firing Distance
Product A
Product B
Product C
Figure 4 – Peak Spray Force using Copley Scientific Spray Force Tester for
Products A, B and C
Force of Nasal Sprays and Metered Dose Inhalers Using the Texture Analyser.
Respiratory Drug Delivery 2006.
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