Lars Asking

Calibration at Different Flow Rates of a Multistage Liquid Impinger

ABSTRACT The multistage liquid impinger (MLI) is an impactor suitable for size-selective characterization and testing of pharmaceutical inhalation products, especially dry powder inhalers (DPIs). The four-stage version of the MLI, which was adopted by the European Pharmacopoeia for testing at 60 L/min, has been calibrated by two different laboratories (Astra Draco AB, Sweden, and AEA Technology, UK), reaching consistent results. The MLI has been extended with an additional impaction stage and all impaction stages have been calibrated at flow rates of 30, 40, 50, 60, 80, and 100 L/min. It is shown that in this flow range, the cutoff diameter depends on the flow rate according to a simplified impaction equation, i.e., the cutoff diameter is proportional to the inverse of the square root of the flow rate. Based on the calibration data and the simplified equation, a cutoff value for any flow rate in the range 30–100 L/min can be assigned. This is an important possibility as a DPI should be tested at a flow ra...

PIGE analysis of sodium in thin aerosol samples

Abstract The detection of sodium in thin (sample thickness mg cm 2 ) aerosol samples using PIGE (particle induced gamma-ray emission) was investigated. In order to find the best energy suitable for a simultaneous PIXE and PIGE analysis, an energy scan from a proton energy 2.20 up to 3.56 MeV was made. The γ yields for the reactions 23 Na (p, p′γ) 23 Na and 23 Na (p, αγ) 20 Ne giving 439 and 1634 keV γ radiation were measured using both a 3 × 3 in. NaI(T1) detector and a Ge(Li) detector. Two proton energy intervals at 2.64 and 2.96 MeV were found to have a fairly stable yield for the 439 keV γ decay and were further investigated. For these energies, the detection limit for Na in thin aerosol samples was determined to be of the order of 100 ng cm 2 when using the Ge(Li) detector.

Evaluation of Aerodynamic Particle Sizer and Electrical Low-Pressure Impactor for Unimodal and Bimodal Mass-Weighted Size Distributions

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. *During the study, E. Gustavsson was affiliated with the Division of Ergonomics and Aerosol Technology, Lund University, Lund, Sweden. **During the study, L. Asking was affiliated with Astra Zeneca R&D, Lund, Sweden.