Ozone Depletion Research Today is a free monthly online journal that collates and summarizes the latest research about Ozone Depletion, including details on hole in the ozone layer, causes, effects.

An Assessment of Beclomethasone Dipropionate Clathrate Formation in a Model Suspension Metered Dose Inhaler.

Bouhroum A, Burley JC, Champness NR, Toon RC, Jinks PA, Williams PM, Roberts CJ

Laboratory of Biophysics and Surface Analysis, School of Pharmacy.

The aims of this study were to investigate and characterize the physico-chemical properties of beclomethasone dipropionate (BDP) crystallized from tricholoromonofluoromethane (CFC-11). Physical interactions in a model pressurised metered dose inhaler (pMDI) system and changes in surface energy after size reduction (micronization) were determined. Although CFC-11 has largely been phased out of use in pMDIs due to its ozone depletion potential, the BDP-CFC-11 clathrate is a stable entity and thus suitable as a model for our initial investigations. In addition, although propellant clathrates have been known for sometime, as far as the authors are aware, their surface energies and adhesive interactions have not been reported. The structure of the clathrate was investigated using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and X-ray powder diffraction (X-RPD). In addition, atomic force microscopy (AFM) was employed to determine the dispersive surface free energy (SE) and force of adhesion (F(adh)) of the BDP CFC-11 clathrate with different pMDI components in a model propellant (decafluoropentane). The dispersive surface free energies for anhydrous BDP (micronized), the CFC-11 clathrate and ball-milled BDP CFC-11 clathrate are (47.5 +/- 4.9) mJm(-2), (11.3 +/- 4.1) mJm(-2) and (15.2 +/- 1.3) mJm(-2) respectively. Force of adhesion results show that BDP CFC-11 clathrates, even after being ball-milled for 2.5hours, have a lower F(adh) compared to micronized anhydrous BDP with different pMDI components. This shows that the formation of the crystalline CFC-11 clathrate is advantageous when compared to the micronized anhydrous form, in terms of its surface energy and potential interactions within a suspension MDI formulation. In the wider context, this work has implications for the future development of HFA formulations with APIs which are prone to the formation of propellant clathrates.

Published 26 February 2010 in Int J Pharm.
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Articles on Ozone Depletion published 25 February 2010:

Diffusion technique for the generation of gaseous halogen standards.   J Chromatogr A.

Halogens are known to play an important role in the tropospheric ozone-depletion chemistry and are of special interest because of their influence on the atmospheric oxidation capacity. In this paper, we investigate the application of a capillary diffusion technique for the generation of gaseous halogen standards like Br(2), IBr, ICl and I(2). The influence of capillary dimension (i.e. length and inner diameter), ambient pressure and headspace volume of the diffusion vessel on the test gas ... [Abstract] [Full-text]

Articles on Ozone Depletion published 22 February 2010:

LCA comparison of container systems in municipal solid waste management.   Waste Manag.

The planning and design of integrated municipal solid waste management (MSWM) systems requires accurate environmental impact evaluation of the systems and their components. This research assessed, quantified and compared the environmental impact of the first stage of the most used MSW container systems. The comparison was based on factors such as the volume of the containers, from small bins of 60-80l to containers of 2400l, and on the manufactured materials, steel and high-density polyethylene ... [Abstract] [Full-text]

Articles on Ozone Depletion published 17 February 2010:

Gas phase reactions of unsaturated esters with Cl atoms.   Environ Sci Pollut Res Int, 17(3): 539-46.

BACKGROUND, AIM, AND SCOPE: Acrylate and methacrylate esters are alpha,beta-unsaturated esters that contain vinyl groups directly attached to the carbonyl carbon (CH(2)=CHCOO- and CH(2)=CCH(3)COO-, respectively) and are widely used in the polymer plastic and resin production. Rate coefficients for Cl reactions for most of the unsaturated esters have not been previously determined, and a good understanding is needed of all the atmospheric oxidation processes of these compounds in order to ... [Abstract] [Full-text]

Interfacial reactions of ozone with surfactant protein B in a model lung surfactant system.   J Am Chem Soc, 132(7): 2254-63.

Oxidative stresses from irritants such as hydrogen peroxide and ozone (O(3)) can cause dysfunction of the pulmonary surfactant (PS) layer in the human lung, resulting in chronic diseases of the respiratory tract. For identification of structural changes of pulmonary surfactant protein B (SP-B) due to the heterogeneous reaction with O(3), field-induced droplet ionization (FIDI) mass spectrometry has been utilized. FIDI is a soft ionization method in which ions are extracted from the surface of ... [Abstract] [Full-text]

Observation of halogen species in the Amundsen Gulf, Arctic, by active long-path differential optical absorption spectroscopy.   Proc Natl Acad Sci U S A.

In the polar tropospheric boundary layer, reactive halogen species (RHS) are responsible for ozone depletion as well as the oxidation of elemental mercury and dimethyl sulphide. After polar sunrise, air masses enriched in reactive bromine cover areas of several million square kilometers. Still, the source and release mechanisms of halogens are not completely understood. We report measurements of halogen oxides performed in the Amundsen Gulf, Arctic, during spring 2008. Active long-path ... [Abstract] [Full-text]

Articles on Ozone Depletion published 9 February 2010:

Consequences of anode interfacial layer deletion. HCl-treated ITO in P3HT:PCBM-based bulk-heterojunction organic photovoltaic devices.   Langmuir, 26(4): 2584-91.

In studies to simplify the fabrication of bulk-heterojunction organic photovoltaic (OPV) devices, it was found that when glass/tin-doped indium oxide (ITO) substrates are treated with dilute aqueous HCl solutions, followed by UV ozone (UVO), and then used to fabricate devices of the structure glass/ITO/P3HT:PCBM/LiF/Al, device performance is greatly enhanced. Light-to-power conversion efficiency (Eff) increases from 2.4% for control devices in which the ITO surface is treated only with UVO to ... [Abstract] [Full-text]

Articles on Ozone Depletion published 3 February 2010:

Binding and activation of N2O at transition-metal centers: recent mechanistic insights.   Angew Chem Int Ed Engl, 49(6): 1018-24.

No laughing matter, nitrous oxide's role in stratospheric ozone depletion and as a greenhouse gas has stimulated great interest in developing and understanding its decomposition, particularly through the use of transition-metal promoters. Recent advances in our understanding of the reaction pathways for N(2)O reduction by metal ions in the gas phase and in heterogeneous, homogeneous, and biological catalytic systems have provided provocative ideas about the structure and properties of metal ... [Abstract] [Full-text]

Articles on Ozone Depletion published 22 January 2010:

Surface ozone measurements in the southwest of the Iberian Peninsula (Huelva, Spain).   Environ Sci Pollut Res Int, 17(2): 355-68.

INTRODUCTION: Photochemical ozone pollution of the lower troposphere (LT) is a very complex process involving meteorological, topographic emissions and chemical parameters. Ozone is considered the most important air pollutant in rural, suburban and industrial areas of many sites in the world since it strongly affects human health, vegetation and forest ecosystems, and its increase during the last decades has been significant. In addition, ozone is a greenhouse gas that contributes to climate ... [Abstract] [Full-text]

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