Aerodynamic particle size

The grade efficiency T of most collectors can be expressed as a function of the aerodynamic particle size in the form of an exponential equation. It is simpler to write the equation in terms of the particle penetration Pf (those particles not collected), where the fractional penetration = 1 — T, when T is the fractional efficiency. The typical collection equation is... 

Flame Photometry and Gas Chromatography (CyTerra) -Aerodynamic Particle Size and Shape Analysis (BIRAL) -Flow Cytometry (Luminex, LLNL) -Semiconductor-Based Ultraviolet Light (DARPA) -Polymer Fluorochrome (Echo Technology) -Laser-Induced Breakdown Spectroscopy -Raman Scattering -Infrared Absorption -Terahertz Spectroscopy -UV LIDAR... 

PJ Atkins. Aerodynamic particle-size testing— impinger methods. Pharm Technol 16 26-32, 1993. 

RW Niven. Aerodynamic particle size testing using a time-of-flight aerosol beam spectrometer. Pharm Technol 17 72-78, 1993. 

The two critical attributes characterizing the performance of DPIs are the imiformity of the delivered dose and the aerodynamie assessment of partiele size distribution. To determine the imiformity of the delivered dose, an apparatus capable of quantitatively retaining the dose leaving the deviee is used. For aerodynamic particle size assessment, a multistage liquid impinger or easeade impaetor is used. All aerosol performance testing must be condueted under defined temperature and humidity conditions. 

Both from deposition studies and force balances it can be derived that the optimum (aerodynamic) particle size lies between 0.5 and 7.5 pm. Within this approximate range many different subranges have been presented as most favourable, e.g. 0.1 to 5 pm [24], 0.5 to 8.0 pm [25], 2 to 7 pm [26] and 1-5 pm [27-29]. Particles of 7.5 pm and larger mainly deposit in the oropharynx [30] whereas most particles smaller than 0.5 pm are exhaled again [31]. All inhalation systems for drug delivery to the respiratory tract produce polydisperse aerosols which can be characterized by their mass median aerodynamic diameter (MMAD) and geometric standard deviation (oq). The MMAD is the particle diameter at 50% of the cumulative mass curve. 

Metered-Dose Inhalers and Nasal Aerosols Content uniformity, aerodynamic particle size distribution, microscopic evaluation, water content, leak rate, microbial bioburden, valve delivery, extractables, leachables from plastic and elastomeric components. 

Tzou TZ. Aerodynamic particle size of metered-dose inhalers determined by the quartz crystal microbalance and the Andersen cascade impactor. Int J Phann 1999 186(1) 71—79. 

It is evident that drugs for application via the inhaled route have to be provided in the form of very small particles. As already described, the aerodynamic particle size should be in the range of 1 to 5 pm for topical delivery to treat the respiratory system (Moren 1987) and ideally below 3 pm to reach the alveoli and to enter the circulation for systemic delivery (Byron and Patton 1994 Patton and Platz 1992 Gupta and Hickey 1991). 

Berry, J., Kline, L. C., Sherwood, J. K., et al. (2004), Influence of the size of micronized active pharmaceutical ingredient on the aerodynamic particle size and stability of a metered dose inhaler, Drug Dev. Ind. Pharm., 30,705-714. 

TSI Aerodynamic particle size spectrometer model 3327provides two measurements, aerodynamie diameter and light-scattering intensity, in the size range 0.5 to 20 pm. The generation of paired data makes the instrument of partieular interest to aerosol scientists. 

Blackford, D.B., Quant, F.R. and Gilmore, J.R. (1994), An Improved Aerodynamic Particle Size Analyzer, Available from TSI, 500... 

Fig. 4 Aerodynamic particle size distribution 0.1 pm < Dp < 5 pm. Results obtained...

The nature of particle deposition forces and their relationship to aerodynamic particle size have been the subject of many studies and reports. A variety of models for aerosol deposition in the respiratory tract have been proposed. The most notable are those of Findeisen [80], Landahl [53,81], and Weibel [1],... 

When a therapeutic agent is formulated into a nebulizer solution or suspension, the quality of the aerosol generated, in terms of aerodynamic particle size, can... 

The aerodynamic particle size of the nebulized dose (i.e., respirable dose delivered)... 

A metered-dose inhaler (MDI) is a complex system designed to provide a fine mist of medicament, generally with an aerodynamic particle size of less than 5 microns, for inhalation directly to the airways for the treatment of respiratory diseases such as asthma and COPD. 

There is much debate about these particular tests and their appropriateness. However, the concept of the use of aerodynamic particle size testing as a compendial test is now well established. Both impactor testing and impingers testing have a role in the development of MDIs, because they are useful tools in studying aerosol clouds and can provide information that leads to formulation optimization (at least in terms of respirable dose). It should be emphasized that these data should not be taken in isolation, and other appropriate particle-sizing techniques should also be used. A more complete discussion of this topic can be found in Chapter 11. 

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