| 1. |
- Bondesson, Eva, et al.
(author)
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In vitro and in vivo aspects of quantifying intrapulmonary deposition of a dry powder radioaerosol.
- 2002
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In: International Journal of Pharmaceutics. - 1873-3476. ; 232:1-2, s. 149-156
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Journal article (peer-reviewed)abstract
- Pulmonary delivery of pharmaceutical aerosols can be quantified using gamma scintigraphy. Technetium-99m, the most commonly used radionuclide in scintigraphic studies, cannot be incorporated into the drug molecule and, therefore, may be distributed differently from the drug itself, particularly if the drug is presented as a solid in a liquid suspension or as a dry powder formulation. This study demonstrated the importance of using conditions relevant to the in vivo situation in the in vitro characterisation of a dry powder aerosol of 99mTc-labelled lactose. The influence of inspiratory flow on the distribution of aerosol within the lungs was investigated in eight healthy subjects who inhaled the 99mTc-labelled lactose at four flows (30,40,60 and 80 l/min). No differences in penetration index (PI) or count density distribution of radioactivity were seen, indicating that regional distribution of aerosol in healthy airways was insensitive to differences in the inspiratory effort exerted by the subject while inhaling the experimental dry powder radioaerosol.
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| 2. |
- Asking, Lars, et al.
(author)
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An electrostatic aerosol sampler
- 1988
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In: Journal of Aerosol Science. - : Elsevier BV. - 0021-8502. ; 19:7, s. 1023-1026
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Journal article (peer-reviewed)
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| 3. |
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| 4. |
- Gustavsson, Eva, et al.
(author)
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Evaluation of Aerodynamic Particle Sizer and Electrical Low-Pressure Impactor for Unimodal and Bimodal Mass-Weighted Size Distributions
- 2005
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In: Aerosol Science and Technology. - : Taylor and Francis Ltd. - 0278-6826 .- 1521-7388. ; 39:9, s. 871-887
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Journal article (peer-reviewed)abstract
- The objective of this study was to investigate the feasibility of the Aerodynamic Particle Sizer (APS) and the Electrical Low-Pressure Impactor (ELPI) to study mass weighted particle size distributions. Unimodal and bimodal liquid test aerosols were produced to a small chamber. Simultaneous measurements were performed with an APS 3320, an APS 3321, an ELPI and a Dekati Low-Pressure Impactor (DLPI) analyzed gravimetrically. ELPI current and mass responses were simulated for lognormal size distributions using a parameterization of the impactor kernel functions. In experiments with a single coarse mode, the mass ratio to the DLPI was between 0.75 and 1.15 for both APS models up to 5 µ m and for the ELPI up to 3 µ m. For larger sizes the ELPI and APS 3320 overestimated and the APS 3321 underestimated the concentration. In experiments with a single fine mode, submicrometer ELPI and DLPI results were in good agreement. However, in contrast to the DLPI all three spectrometers showed a significant mass fraction above 1 µ m. In experiments with a bimodal size distribution, the mass ratios were altered compared to single coarse mode experiments. Simulations showed that uncertainties in ELPI measurements of larger particles occur when concentrations of small particles are high. Several mechanisms that may bias ELPI and APS measurements are described. With knowledge of these, ELPI and APS 3321 can, under many circumstances give accurate time-resolved mass size distributions for particles smaller than 3 and 5 µm, respectively.
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| 5. |
- MARTINSSON, BENGT G., et al.
(author)
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A relative humidity processing method for the sampling of aerosol particles with low growth‐ability
- 1992
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In: Tellus. Series B: Chemical and Physical Meteorology. - : Stockholm University Press. - 0280-6509 .- 1600-0889. ; 44:5, s. 632-644
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Journal article (peer-reviewed)abstract
- A method for the fractionation of aerosol particles with respect to size and ability to grow with an increased relative humidity has been developed. The system consists of cascade impactors, diffusion driers, a humidifier and a temperature stabiliser. Diffusion driers were designed and the vapour penetration was modelled below 20%. A humidifier which can be operated with an output relative humidity above 95% was developed. Flow‐rates up to 51/min can be used and the relative humidity can be controlled within approximately 1%. The ability of the system to fractionate aerosol particles with respect to growth with relative humidity was investigated. The equivalent aerodynamic diameter growth factor for sodium chloride was determined to 2 at a relative humidity of 98%, in good agreement with theory. The growth is used to collect particles with no, or limited growth with increased relative humidity in separate fractions for chemical characterisation. This is obtained with an impactor stage operated at high relative humidity followed by a diffusion drier and an impactor stage with a factor of 1.4 lower cut‐off diameter operated at low relative humidity, where the particles with low growth‐ability are collected. The system was in operation during the EUROTRAC sub‐project Ground‐based Cloud Experiment (GCE) at Po Valley, supplying important information on the particle size related scavenging and the elemental composition of particles with a low growth‐ability.
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| 6. |
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| 7. |
- Rissler, Jenny, et al.
(author)
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A Methodology to Study Impactor Particle Reentrainment and a Proposed Stage Coating for the NGI.
- 2009
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In: Journal of Aerosol Medicine and Pulmonary Drug Delivery. - : Mary Ann Liebert Inc. - 1941-2703 .- 1941-2711. ; 22:3, s. 309-316
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Journal article (peer-reviewed)abstract
- Abstract Background: Mass-weighted aerodynamic particle-size distribution (APSD) is a key attribute for pharmaceutical products developed to deliver drugs to or through the lungs. In development and quality control, APSD is primarily determined using multistage cascade impactors. For impactor techniques, particle reentrainment is critical because it may lead to an overestimation of the respirable fraction. To avoid reentrainment, the collection surfaces need to be coated with a suitable material. Methods: In this study a method was developed to test flow dependence of particle reentrainment in the Next Generation Pharmaceutical Impactor (NGI) at flow rates ranging from 20 to 80 L/min, and was used to test three coating materials: glycerol coating, aqueous coating with, and without soaked filter paper. Uncoated cups were also tested. In the experimental setup a Vilnius Aerosol Generator generated a flow-independent dry powder aerosol, consisting of micronized insulin. Results: The glycerol coating was not well suited to reduce particle reentrainment at flows >/=40 L/min. The soaked filter paper coating was found to give nearly the same particle size distributions regardless of flow and was therefore judged to be the best of those tested. Using liquid only, without the filter paper, gave the same particle size distributions as soaked filter paper for flows /=60 L/min particle reentrainment increased with flow. However, for most applications liquid coating reduced particle reentrainment to an extent at which further reduction was irrelevant. Particle reentrainment was prevalent for uncoated cups at all flow rates tested. Conclusions: This study shows the advantage of using a stable and flow-independent aerosol generation method to examine particle reentrainment at various flows through the NGI. For insulin dry powder, the use of an aqueous solution as cup coating, preferably with a filter, reduced particle reentrainment to a minimum. The results were confirmed in a study with a DPI.
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